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General Forums => The Mess Hall => Topic started by: RNandKT on December 30, 2005, 03:10:46 PM
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Has anyone tried using a 3.0L comercial GM motor to rebuild in place of the stock 2.5L. I understand the block and piston size for the 3.0 is nearly the same as the 2.5L. So would it be possible to get a 3.0L from a boat or commercial vehical rebuild it using the it's stock longer crank shaft, bore it to .020/.030/??? put in a nice cam etc etc then bolt on all the stock externals of the 2.5L (i.e. head fuel injection pulleys power steering etc etc) and come out with a 3.1/3.2/??? stroker 4 cyl for my YJ?
I understand that just using the crank and con rods into the 2.5 block would not work because it would have clearence issues with the distributer??? So the 3.0 block would have to be retained???
I think if this was all done "stroking it", nice cam, bored out, maybe some rocker rollers for the head, (along with some of the other external upgrades, like a throttle body from a 4.0, bigger injectors, and a nice header) perhaps the little stroker motor could be pushed into the 200 hp range? That would save all the headache of rewiring in a motor swap, and put it into hp range of the stock 4.0.
Any info or thoughts on this would be welcome.
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Welcome,
I see you made it over.
Sorry I got a little to excited and posted up
here http://www.4bangerjp.com/forums/viewtopic.php?t=720&highlight=
Hopefully, someone will answer one of us.
But I found some good info just by googling.
Turns out that the motor are pretty much the exact same motor.
From what I read the 3.0L block can be a direct bolt up for the 2.5L with the exception of the distributor and the flywheel. You would just re-use yours from the 2.5L.....
Go over to the other thread and check out what I found on Google.
Good info.
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Oh, also, the cams that come in the 3.0L is supposed to be the most radical you can get but I haven't verified the lift yet so right now that is just hearsay.
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Yeah this forum is awsome already been reading a ton of stuff on here. It's nice to get away from all the people on other sites who just dawg everyone who doesn't think you have to spend lots of money buy huge axles and massive hp v8's. It's cool to find other people who like to take what jeep put in and just tweak it a bit.
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Yeah this forum is awsome already been reading a ton of stuff on here. It's nice to get away from all the people on other sites who just dawg everyone who doesn't think you have to spend lots of money buy huge axles and massive hp v8's. It's cool to find other people who like to take what jeep put in and just tweak it a bit.
Exactly! That's why Jeffy created this site. You get slammed hard on other threads for just asking questions when that is what we are all there for.
This site is very friendly and has a good bit of knowledge about Jeeps and the little 2.5L...
Glad to have a new recruit.
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I see you have the AX15 behind your 2.5L. Did you get the idea from YJ4rox?
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Yeah I read that thread, i actually started mine the same time he did. So most of the problems he ran into with the pilot bushing and the clutch slave cylinder i learned the hard way as well. But I stayed with the stock slave cyl in the end, I just made my own custom spacer using tom exhaust pipe. But it was nice because I didn't have to find what belhousing I needed and what clutch disc.
I also got my ax-15 out of the only year they put it in a grand cherokee, (rebuilt out of a 93) supposedly the internals are beefed up a bit.
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Cool, YJ4rox is parting out his YJ and I bought his full kit from him for my Dad's Jeep conversion. He just opened the boxes tonoght and YJ4rox packed everything nice and clean and included EVERYTHING for the complete conversion.
Got the tranny and all the parts for $660 shipped. Just had to buy the Master cyl. Line kit and shorten the DS.
Gonna be easy to throw this one in....
It's a good thing you already did that conversion especially if you are adding a built 4 banger. That tranny should hold up a lot better.
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Yeah I am trying to get my drivetrain preped BEFORE I throw hp at it so I don't end up stranded on the trail too much.
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Well, I mentioned in the other thread that it can be done and has. But Emission wise, it's not legal.
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Well I would like to know the specifics of it. Which block did you use the 2.5 or the 3.0? What years are compatable? What flywheel? What cam to use and where to get it? etc etc etc.
Also how were the results? I think if you did this stroker with some of the other things as mention in the other 2.5 rebuilding threads, you could really make a nice motor.
And out of curiosity why would it be illigal people make stroker motors all the time? Is that a california thing because I live in OR currently and will be in UT permantly in the future. And as far as I know in both places as long as you stick to stock engines you can do pretty much anything to them (short of NOS) as long as it passes the emissions test.
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I haven't done the swap but I've seen it done before.
It's illegal because the engine was never used in a street going vehicle. So there are no emissions on the engine. Basically if it hasn't got the DOT's seal of approval, it ain't Kosher.
Not to mention installing a carburated engine into a EFI vehicle is seen as going backwards emisison wise to the DOT.
But then, not every state enforces emissions.
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Well I had actually had in mind of using the 3.0 block and then using my head fuel injection etc from my stock engine. Or if it would work just to use the crank and con rods and put them in my block. I only want to extend the stroke of my engine increase the displacement.
Do you think that would work? I would still keep all proper emissions equipment on my vehical.
I would think if I had my head rebuilt right and if I put a different cam in the 3.0 where the carburated 3.0 is rated at 140hp with those changes and MPI injection maybe it would be closer to 190-200. Plus because it was a longer stroke it would be considerable more torque since the 3.0 carburated is 171 it should be closer to 210.
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The biggest problem is that the engine is a GM and the Jeeps is an AMC. They aren't even remotely in the same family. This means that the dimensions of the block would have to be almost identical. Spacing between the cylinders need to be the same also. Then you have to match up the jackets in the block and all the push rods will have to align. I think it would be a miracle if it all happened to work.
You'd be better off getting a TBI and a stand alone computer like a Mega Squirt to run the EFI, I think. At least matching a TB onto the intake would be easier.
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Hmm ok well good to know won't work. Do you know anywhere you can get a crank shaft that will stroke the 2.5?
Thanks
Ryan
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Well, I think the only option for a crank is to locate a Mopar Performance Crank. It's listed in the FAQ. I've never seen one though.
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are the belhousing bolt patterns on that gm 3.0 the same as the amc 2.5?
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I'm not positive but I'd suspect it uses a standard 60 Degree Bellhousing bolt pattern.
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Hmmm i am going to have to do some more research into the 3.0 L engine and see whats common etc.
I do know the the GM 2.5 and the 3.0 share the same bellhousing pattarn.
How much is common between AMC's 2.5 and GM's? Anything swappable? Heads, distributers etc etc?
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If the 3.0L shares the 2.5L Pontiac Duke's pattern then it will match the 2.4L AMC bellhousing. Like I said before the AMC and GM do not share anything. For the GM, the exhaust ports are on the passenger side.
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The amc 2.4L?
The "marine" 2.5 and 3.0 have the exh and intake ports both on the drivers side. perhaps that could work. <--- slim chance.
but is there a possibility you could put a head from a fuel injected GM 2.5 and have it be a simpler wire up to the jeep?
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maybe I am just beating a dead dog here, but I just want to look at it every way.
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Whoops, that should have been 2.5L.
Like I said before you're best chance is to use a stand alone EFI. I believe the RBI's of the 2.8L and early 5.7's are like this.
The only other concern would be if the engine runs in reverse or not. I'll have to dig out that article about the CJ with the Mercruiser 3.0L and see what they say.
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Well almost all boat motors do, but that is a matter of a different cam and so on. I believe the 3.0 was also used in commercial things such as tractors whatever, where it ran normal rotation. Plus you should be able to use a cam from a chevy 2.5L to run normal rotation ... right?
I'm starting to think I'm pushing this too far though. My best guess is that it would bolt up to the tranny but getting the intake to work and still keep the MPI would be near impossible.
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Another question though, the "Mopar Performance crankshaft" does it actually increase displacement? I.e. is it actually a longer stroke requiring longer con rods?
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if the mopar crankshaft did increase displacement via a longer stroke, it would require shorter connecting rods.
what about simply using the 3.0L engine and doing away with the 2.5L entirely?
i was looking at how some guy in canada put 4.2L parts into his 4.0L to stroke it. someone correct me, but given that the connecting rods are shared between the 2.5 and 4.0--according to what i've found on the net--then it would be possible to use the shorter 4.2 connecting rods on a 2.5L. then it is a matter of getting a longer stroke 2.5L crankshaft. i've been wanting to see if the 4.2L and 2.5L share similar patters (assuming that the 4.0 and 2.5 are the same with the exception of 2 more/less pistons, though i've read that they're not). nonetheless, it would be great to simply machine a 4.2 crank to be a 2.5L pattern. if possible, then it would be possible to stroke the 2.5L slightly.
i did some calculations and the displacement increase was small (maybe 2.7 or something), and you would still need a spacer between the head and the block. then again, it would be cool to weld a machine a different stroke on the 2.5L crank and use shorter rods--4.2 or another?--and get more out of the engine. on some mopar site, it says that the 2.5 is already stroked from the smaller 2.-something, and that stroking it would be impossible or very difficult.
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Yeah wasn't thinking about shorter not longer con rods. But yeah that would be awsome. So do you think it would be possible to have a 2.5 crank custom machined to a longer stroke?
I don't know about the 2.5 and 4.0 rods being the same? But I do believe other than the length the 4.2's and the 4.0's are the same. So maybe it could be done. Who would you talk to about finding out?
Assuming all that could be done, do you think that as long as you didn't deck you block or head (at least very little) that you'd have enough clearance? It would probably push the commpresion up with out having to deck it anyway .. right?
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right, i think that increasing the deck was to keep the compression right. it's been a while since i tried computing the stuff out. i contacted a machine shop and they wanted 2-grand to grind a crank with a longer stroke. too much for me.
maybe getting shorter rods, a longer crank, and off-set pistons, you can stroke the 2.5L.
i'll look up my notes to see what scheme i was trying to create. also, try this formula: piston size x piston size x crank stroke x .0031416 equals displacement in cc's.
so, 88mm pistons and 90 mm crank would be: 88x88x90x.0031416 or about 2040 cc's or a 2.0L engine.
i started with this to figure how much more stroke and piston size would be required to get to a given displacement. you can also apply factory specs to figure what is the least that can be modified to get the most increase.
then, i got this formula to determine TDC for pistons (can't recall for sure right now), and using it i got the deck height increase needed to keep everything in line.
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if the mopar crankshaft did increase displacement via a longer stroke, it would require shorter connecting rods.
what about simply using the 3.0L engine and doing away with the 2.5L entirely?
i was looking at how some guy in canada put 4.2L parts into his 4.0L to stroke it. someone correct me, but given that the connecting rods are shared between the 2.5 and 4.0--according to what i've found on the net--then it would be possible to use the shorter 4.2 connecting rods on a 2.5L. then it is a matter of getting a longer stroke 2.5L crankshaft. i've been wanting to see if the 4.2L and 2.5L share similar patters (assuming that the 4.0 and 2.5 are the same with the exception of 2 more/less pistons, though i've read that they're not). nonetheless, it would be great to simply machine a 4.2 crank to be a 2.5L pattern. if possible, then it would be possible to stroke the 2.5L slightly.
i did some calculations and the displacement increase was small (maybe 2.7 or something), and you would still need a spacer between the head and the block. then again, it would be cool to weld a machine a different stroke on the 2.5L crank and use shorter rods--4.2 or another?--and get more out of the engine. on some mopar site, it says that the 2.5 is already stroked from the smaller 2.-something, and that stroking it would be impossible or very difficult.
The guy's who are stroking their engines are using the 4.2L crank. This engine is in the same family as the 4.0L and 2.5L. This is wht Mopar was able to make an EFI kit for the 4.2L.
The problem with the 2.5L is that there are no other engine's that share the same profile. If you bored the engine to .060" you'd get a 2.74L.
Honestly, I don't think it's worth it to use the 3.0L unless you're going to use it stock. I'm not sure if the 3.0L shares the same parts as the 2.5L either. The more common 2.5L is a Pontiac engine and usually a bit different like the Buick's.
I think the 3.0L is a dead end.
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Well thanks guys for all the info, I don't think spending 2000 to get like .2 more liters is worth it. I suppose if I want more displacement I will either have to just bore it, or go the old fasion way and swap in a bigger motor. If anyone does come up with a way to stroke it a little more affordably, I still love to hear about it. It would make a great compliment to the .060 bore.
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Well ok......I guess i will still stick with the bore .60 over and shave the head, polish and port and balance the bottom end and be done with it.
After that and my Inertia ring I should have enough power to hold highway speeds no problem.
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Only if you're geared right. :wink:
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Only if you're geared right. :wink:
Yea, I am not using my 5th gear right now except over 75mph. LOL!!
I hope to go to 4.88's eventually but will most likely rebuild the motor first...
On another note, I think my AX15 is getting ready to take a dump cause I am getting A LOT of noise between in nuetral and when I push in the clutch around 4th and 5th gears. Sounds like gears clacking together. Gonna need to rebuild or find a nother AX15 for cheap. $250 or less. Don't have a lot of money left after doing everything else to the Jeep I have lately. Not happy about that since I have only had that tranny in for about 4 months. Still drives just fine BUT make too much noise for my comfort level. Gonna add another quart of Redline and see if that helps.
What's weird is it got this loud after my SOA. Almost seems as if the TC lowering kit might have made the fluid sit at a different level that's another reason for adding the extra quart. The other is it just sounds better in general and I know it will hold it.
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::::Revival:::::
I did some reading and would be possible to have a 4.2 lt cranckshaft cut down the 2 cyl and then have it setup for the 4?
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I don't think so. I believe they use a different profile and I think 1 & 6 are removed to make a 2.5L. You'd also have to be an outstanding welder to put those pieces back together and balance it. back up. At that point it would probably be cheaper to get a custom crank.
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well a custom crank would be cutting welding (and balanceing) every cyl's so would'nt it be worse than cutting an welding and balenceing the ends? I am no mahcinist or pro welder or a good engine guy for that matter, just thinking if you were having a shop custom make your crank that that might be the way to do it. (more of a base to start with.)
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It would probably be cheaper to swap in a larger engine.
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thats a good point.
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Hey guys, just wanna chime in on some additional info regarding a stroker crank. There was a guy who races a 2.5 XJ in the Jeepspeed competitions that was working on it, but I haven't heard any further developments. Didn't sound cheap though. He could be just welding and offset grinding the crank like you guys are mentioning. No too much info but, here's a link to read up:
http://www.jeepspeed.com/forum/YaBB.pl?board=tech_1;action=display;num=1127536495
Also I'm not sure what you guys think of this, but I've been cautioned by my machinist that the max amount I should bore out is .030 with our motors. I'm told there are two reasons for this. Our cylinder wall thickness is about 3/16 of solid useable casting. Given the tolerance in core shift (the bore being concentric to the cylinder casting during manufacturing), there could be a risk to making the walls too weak if boring over .030. I never thought the 2.5 block was too different from other motors from a manufacturing standpoint, and know that boring .060 is common on other motors, so I'm wondering what is fact.
The second reason I'm told is that the no.1 cylinder is relieved (shaved) to clear the water pump vanes. Although this relieved area is not the at the thrust surface of the cylinder, and not the heaviest loaded part of the cylinder, it should be considered. This seems to be true when I inspected my block.
(http://i30.photobucket.com/albums/c345/caligold/block.jpg)
My machinist recommended sleeving the cylinders if I want to significantly increase the bore (4.00 or 4.125 inch chevy pistons) and shaving the vanes on the water pump if clearance becomes a problem, but at 100 dollars per jug, I don't know if it's the best use of my money. Chevy pistons seem to be a feasible alternative in that they have a .020 lower compression height, and will work with the stock AMC rods if the small ends of the rods are machined just a bit...given that you got the wallet to cover the sleeving.
My spare motor is completely apart with the bare block on the engine stand. I'm still trying to gather info and decide what I want to do about increasing the displacement, and been reading your posts to find out what seems to work. Thanks for all the info guys. I'm glad us 4 bangers have a place like this place to swap ideas. Although it's another one of my long term projects, I'll try to keep you guys posted.
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Oh BTW, Chevy SB guys have their cranks offset ground without welding and use rods with smaller journals. The machining price is reasonable. at $200 for a V8 crankshaft.
Adding material by welding then offset grinding is between $425 to $725 for a SB Chevy depending on how much you stroke you want.
http://www.flatlanderracing.com/crankshaft_services.html
The AMC crank shouldn't cost any more. Probably less. Then use the 4.2 pistons and rods...
Maybe could work?
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How much "stroke" is gained by "offset grinding"? I have heard that term before. There is a significant difference in the length of 4.0 (or 2.5) con rods and 4.2 con rods. So if the offset grinding is not significant enough, you would have to really deck your block to get the pistons to come up high enough in the cyl right?
Any displacement change numbers from these small block chevys? What kind of con rods do they use. Are we talking about like chev 350's and are they using con rods from SB 400's ? This would be nice to know so we could compare it to a whole crankshaft swap as in a 383.
Great info I would like to explore this option since it is an affordable option. I am still on the fence between an I-6 swap and building up my 4.
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I was just reading the services offered from flatfender racing looks like that really might work, does anyone know the legth difference on from the 4.2 rods to the 2.5's. Flat fender racing can offset grind most of the v8 crankshafts around .2" I think that is close to what would be necessary to use the 4.2 rods?
Theoretically speaking if one were to bore the engine closer to thr recommended .030 (which puts displacement areound 2.6lt) and were able to stroke it with the 4.2 rods that would push displacement to around 2.75 - 2.8 L? That combined with other things (such as a hotter cam 4.0 TB etc etc) could probably make a reliable 180-195hp and similar torque numbers?
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Just checked some specs and here's what I got:
The rods from the 4.2L will work. The diameters of the small and large ends are the same (.929" and 2.208" respectively). The length (center to center) of the 4.2L rod is 5.875" and the length of the 2.5L rod is 6.125". The difference in rod length is .250".
The stroke of the 4.2L is 3.895" and the stroke of the 2.5L is 3.190" which is a difference of .705". Half of this amount is the "theoretical" offset grinding for the rod journals which is about .353".
There is a deck to piston spec of about .015" for the 4.2L (piston lower than top of block) while the 2.5L is at zero and the compression ratio for the 4.2L is 8:1 while the 2.5L is 9.2:1.
Also a correction to my previous post...you would not be using the 4.2 pistons since they are 3.75" in dia whereas the the 2.5L is at 3.875 std.
I still need to figure out what the "real" value for offset grinding would be considering that I would want the final compression ration at about 9.5:1. I would guess I would reduce the theoretical offset figure slightly to get this kind of CR. I'd probably cc the combustion chambers and the piston tops with a burette to be absolutely sure about the true offset grinding number.
From my calculations this would yield me to about 3 liters using 2.5L pistions (with .030 overbore), the 4.2L con rods, and an offset grind of the rod journals of let's say ...about .345" (which BTW will require welding). I think at the very least you could get an additional 30 hp even with stock everything else. Cam, TB, head work, ... even more hp.
Okay now here are some unanswered questions I'm still wondering about:
1. The 2.5L has a shorter stroke than even the 4.0 where this kind of stroke mod is common. I need to make sure the cylinder bore is long enough to handle the full stroke of this modified crank.
2. Will it clear the rest of the block at the oil pan flange, etc... The 4.0 block needs to be clearanced at the bottom of the cylinders just a tad.
3. How will the MPI system take to the severe increase in displacement? I need to read up more on the results of people who did the 4.0 stroker mod to find out.
Still working on the figures, but I'm looking for any guinea pigs who wanna try first :lol:
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Well as far as the increaseddisplacement, I know a lot of the peopl who make the 4.6 liter stroker that results from a 4.0 and 4.2 together, often upgrade their injectors to the 24lb Ford injectors. Other than that no other major stuff is really required. Some get the larger 62mm throttle body but the stardand works fine. But apparently with the increased displacement and a hotter came the stock injectors are a little lean.
Now considering the 4.2 con rods, that much stroke increase would require one of their welded cranks which on their web site for v8's was about 450 or so. But you mention the 2.5's stroke was shorter than the 4.0's, how much? Would the 4.0's con rods be a better option for the offset ground crank? I think you will find as mentioned before that more than a .2 liter increase in stroke will probably be impossible due to clearence issues. I don't think I would do the stroke increase unless I was able to do it by just the offset grind. But I might be your test dummy if you want to go that route. But I think I want to at least go .040 over piston wise. And I think some major head changes. Thats were a lot of hp is lost anyway.
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Besides there are other things that can be done to affect hp and torque that don't require displacement increase such as knife edging your crank, and having everything balenced. etc etc
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Well RNandKT, the stroke on the 4.0 is 3.413" whereas the stroke of the 4.2 is 3.895". The 2.5 is at 3.19".
To offset grind amount for the 2.5 crank to the 4.0 stroke, would be about .110. I would guess it would bring the motor to about 2.7L.
With welding and offset grinding costs betwee 400 to 500 dollars, and some reasonable bookkeeping, it's probably not gonna be worth it unless you have a lot of disposable income. Same with sleeving the cylinders for bigger pistons. That's probably why there isn't too much information involving these engine mods. Oh, the voice of reason...
I'm not in the position to pour money into a custom motor with unknowns, so I'll think I will spend the bulk of my expense into a good camshaft from either Hesco or Clifford. Combined with .030 overbore, milling the head, and a little cleanup of the ports and combustion chambers, and like you mentioned, balancing and knife edging.
I think it could be a nice increase in power and torque while maintaing good reliability. Even this and all the other parts involved in a rebuild would probably run about $800. I would be happy with 20 to 25 extra hp. Hopefully enough to get up those highway grades, and keep up on backroads on my way to the trails.
Still very interested in hearing about others who've modified the internals of their motors. I
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Well I think using the 4.0 con rods and offset grinding as apposed to welding and using the 4.2 is a much better idea. (200 versus 625 for thatmuch of a change). Plus I have done some research and it appears as though 2.7 is the moststroke you can get before some major clearence issues. I am leaning towards this heavily.
I very much apprciate everyones information. If and when I get to my rebuild I will keep everyone posted.
Thanks
Ryan
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wow, everybody said I was crazy for spending so much time building my motor but you guys are talking way further out there. I'm not sure if it is worth all that effort to stroke it but I'd like to see it work. By the way the 30 bore is probably a bit on the careful side because most four cylinders can actually be bored in the 80-100 range and be ok if run properly. My machinest told me about himself taking chevette motors and boring them 120 over. Now mind you that is double what I did but you get the picture. Four cylinder blocks have thicker cylinder walls that larger motors to start because of the high rpm's. My motor is 60 over and sporting plenty of other goodies(cam, shaved deck, port and polish head, custom valvetrain, etc..) and I run it to almost 7000 rpms with no problems but I am also the first person I have seen to build this motor that far and we'll se how it does in the long run. But I outrun 4.0 and I spent under $2000.
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Offset grinding..... You have to start with a rod that has a smaller large end than the rod thats being currently used. Thats how you can offset grind. With that being said... If you can find one with say .100 smaller you can offset grind the crank by an aditional .095. The reason for the .005 less is you have to allow your self enough materal to ensure that all the strokes come out to be the same. Other wise it has to be welded to add enough materal to come up with extra stroke.
I just come across this forum and have spent the last couple days researching more indepth what I can do to my 2.5. Still not much more than I already know... I've had my TJ for about 6 yrs now and love my 4banger but its time for more power. I will stroke this motor and bore it .060 over and cam it. The rest of the known mods have been done already 4.0 throttle body header stage 3 jet chip bla bla bla.. Its time for all or nothing.
My hat is off to YJMech for going .060 on his motor, I read about how people say you shouldn't do it. If that was the case they wouldn't offer the pistons..... I was a machinist for 15 yrs and 4 of that I had a side job in a engine shop. I have built several motors to say the least and some were strokers and they have ranged from chevy to ford to VW aircooled. Not to toot my own horn I'm just trying to say it can be done. I just need to dive into the books and find the right rod and piston.
I love this forum so far, you guys are great. its nice to have a place were someone isn't saying put a small block in it. I'm with YJMech do what cant be done..... or was suposable cant be done... Lookig forward to haveing some fun here, I'll keep everyone up to date with pics... the only thing that sucks is I travel with work but its looking to be slow for a few months ...hopefully its long enough to get this stroker built lol :-) and have some fun with it.
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Offset grinding..... You have to start with a rod that has a smaller large end than the rod thats being currently used. Thats how you can offset grind. With that being said... If you can find one with say .100 smaller you can offset grind the crank by an aditional .095. The reason for the .005 less is you have to allow your self enough materal to ensure that all the strokes come out to be the same. Other wise it has to be welded to add enough materal to come up with extra stroke.
I just come across this forum and have spent the last couple days researching more indepth what I can do to my 2.5. Still not much more than I already know... I've had my TJ for about 6 yrs now and love my 4banger but its time for more power. I will stroke this motor and bore it .060 over and cam it. The rest of the known mods have been done already 4.0 throttle body header stage 3 jet chip bla bla bla.. Its time for all or nothing.
My hat is off to YJMech for going .060 on his motor, I read about how people say you shouldn't do it. If that was the case they wouldn't offer the pistons..... I was a machinist for 15 yrs and 4 of that I had a side job in a engine shop. I have built several motors to say the least and some were strokers and they have ranged from chevy to ford to VW aircooled. Not to toot my own horn I'm just trying to say it can be done. I just need to dive into the books and find the right rod and piston.
I love this forum so far, you guys are great. its nice to have a place were someone isn't saying put a small block in it. I'm with YJMech do what cant be done..... or was suposable cant be done... Lookig forward to haveing some fun here, I'll keep everyone up to date with pics... the only thing that sucks is I travel with work but its looking to be slow for a few months ...hopefully its long enough to get this stroker built lol :-) and have some fun with it.
Wow dead thread, although I've read it once before... some cool stuff here!
Please explain more on offset grinding, I'm intrigued! Got a second engine, too!
My current engine is .030 over, most of the power difference between it and the last is just the fact that it's fresh... i wanted a performance cam and springs, but I needed it done fast and I was short on money... next one will be a more serious build.
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Yea I noticed after I posted the answer the thread was old, I seen you was asking alot of questions when you did go threw yours. Nothing wrong with that. I guess I'll start a new thread on this subject. I've spent the past few days reading pretty much everything to offer on rebuilds in this forum just thought I would throw in my 2 cents.
Well basically to off set grind you have to have a rod journal thats smaller on the rod your going to use in the build. By doing this it allows for moveing the stroke. Draw a circle then draw another smaller one inside and put the end of the smaller one on the edge of the bigger one. This will give you a better idea of what I am trying to get across.
Also with useing a smaller rod journal you have less friction than the larger stock journal, on these motors it isn't a issue your not spinning it to 9k like a race motor, we are pretty much wanting to make our max power around 4 to 4500. I'm running around 3200 on the highway, and thats not very often. I mostly use mine jeep offroad and very seldom see's anything over 2500 to 3000. We mostly woods ride and hill climb bla bla bla. I just want to be able to put it in 5th and not down shift the thing when I do decide to take it for a cruise.
I picked up another motor to go threw so the jeep dont have any down time while I'm doing this project, Ended up finding a motor, trans and tcase for 300 only had 80k on it but was out of a 1990, mine is a 97. I dont think there will be many issues witht the year differance but we wil find out.
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Yea I noticed after I posted the answer the thread was old, I seen you was asking alot of questions when you did go threw yours. Nothing wrong with that. I guess I'll start a new thread on this subject. I've spent the past few days reading pretty much everything to offer on rebuilds in this forum just thought I would throw in my 2 cents.
Well basically to off set grind you have to have a rod journal thats smaller on the rod your going to use in the build. By doing this it allows for moveing the stroke. Draw a circle then draw another smaller one inside and put the end of the smaller one on the edge of the bigger one. This will give you a better idea of what I am trying to get across.
Also with useing a smaller rod journal you have less friction than the larger stock journal, on these motors it isn't a issue your not spinning it to 9k like a race motor, we are pretty much wanting to make our max power around 4 to 4500. I'm running around 3200 on the highway, and thats not very often. I mostly use mine jeep offroad and very seldom see's anything over 2500 to 3000. We mostly woods ride and hill climb bla bla bla. I just want to be able to put it in 5th and not down shift the thing when I do decide to take it for a cruise.
I picked up another motor to go threw so the jeep dont have any down time while I'm doing this project, Ended up finding a motor, trans and tcase for 300 only had 80k on it but was out of a 1990, mine is a 97. I dont think there will be many issues witht the year differance but we wil find out.
Different cam at least, the 90 might have a higher compression ratio... Let me try to remember how it goes...
TBI 86-90 2.5 has 9.2:1 compression ratio, YJ OBDI is 9.1:1, XJ is 9.2:1, OBDII XJ and TJ 2.5's are 9.1:1. I'll check out my FSM soon to confirm...
Start an engine build thread of your own and I'll chime in on external differences you'll have to deal with.
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Fly wheel is a issue do to the crank sensor. Cr is going to have to be ajusted due to the .060 over, that added volume will raise it alone, the added stroke will raise it again. Deck height will need to be adjusted for proper quench, but wont know untill I CC the head to find that out. Pistons might have to be cut a little to put it were i want it. Cam sounds a little big but you have to remember the bigger the displacment the more it tones down the cam. Its not going to be easy........
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Fly wheel is a issue do to the crank sensor. Cr is going to have to be ajusted due to the .060 over, that added volume will raise it alone, the added stroke will raise it again. Deck height will need to be adjusted for proper quench, but wont know untill I CC the head to find that out. Pistons might have to be cut a little to put it were i want it. Cam sounds a little big but you have to remember the bigger the displacment the more it tones down the cam. Its not going to be easy........
Reuse the 97 flywheel, it'll bolt right up no problem. I'm fairly certain there is more than one size head gasket, and there is a WIDE selection of pistons and rods thanks to the 4.0/4.2 interchangeability.
Wont offset grinding to the 4.0 stroke and using 4.0 rods get you the same CR as the 4.0? I'm pretty sure the head volume and head gasket are the same between the two. The CR will actually go down to 8.7:1 if they are, but the quench height will go up, so you'll want to deck the block and raise the CR higher than 9.2:1, so you can run dished pistons to increase volume and bring the CR back to stock... correct me if I'm wrong, but I believe that is the correct train of thought?
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yea your on the right path, provided all jeep parts were used. It could end up being a nissan rod or anything at this point. This is what is the hold up is. I'm basically looking at every rod on the market to see whats the easiest and what will provide the most stroke. A short rod puts more side load on the piston, thats causes friction, premature wear, over heating issue's. Plus it limits the rpm range to 5k. A longer rod could take away from bottem end TQ, but hold up very well at higher rpms. Some were there is a happy medium, its just a matter of finding the needle in the hay stack.
I'm pretty sure the head will work with the TJ injection, I have one on the way, another intake that is picked it up for 20 bucks. I also figured the flywheel and bell houseing can be used from mine unless I can find a deal on one. These are minor issues, but there is easy fixes and work arounds. The pullies and externals will all be swithed over, I'm really just interested in useing the block and head basically and what ever internals can be rebuilt or reused.
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This thread came at a good time. Thursday evening I was talking with a long time mech that works at the Dodge/Jeep dealership, he also builds hi-per 4x4s, about more power/displacement for the 2.5L. he said that it was possible to use the crank and rods and flat top pistons out of the 2.8L Mercruiser engine. I did a search and this engine is a diesel. I've just got back into town and haven't asked him if that's the right one. If it is I can see a second engine being built. I have a friend at a marine shop that could get me an old engine. Hopefully I'll be able to check for sure this week. I'm like ya'll I'd like to keep the I4 just build it up.
JR
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This thread came at a good time. Thursday evening I was talking with a long time mech that works at the Dodge/Jeep dealership, he also builds hi-per 4x4s, about more power/displacement for the 2.5L. he said that it was possible to use the crank and rods and flat top pistons out of the 2.8L Mercruiser engine. I did a search and this engine is a diesel. I've just got back into town and haven't asked him if that's the right one. If it is I can see a second engine being built. I have a friend at a marine shop that could get me an old engine. Hopefully I'll be able to check for sure this week. I'm like ya'll I'd like to keep the I4 just build it up.
JR
If this is true, all the offset grinding talk isn't really necessary (depending on how much extra stroke the 2.8 crank provides). I'm VERY intrigued.
I'm running a later model intake with later model pullies and accessories, there were only minor problems with valve cover mounts and such, but I resolved them... make sure to swap your later-model engine mounts, or you wont be able to mount the voltage regulator on the alternator. I'm sure there are other minor challenges that you'll need to figure out, good luck!
Wow, just read that the mercruiser stroke is 3.94! I'm fairly certain that with .030 that would make a 3.1L engine... I'll do some real calculations, that was just off the top of my head...
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3.149 @ .060 bore motor would be 3.94 x 3.94 thats a square motor my friends, when your talking max TQ out of a package thats how its done.
I'm still on my first cup of coffe, need to look intot to this 2.8 a little more, but this is VERY interesting to say the least. I've been looking at more involved options. :smokes:
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192.149 cubes :hitit:
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Ok this is the storey its the 2.8l merc made from 1987 to 1989, its a gas motor and based off the gm iron duke... thats all pretty promising. I cant find the cranks and rod details on line though. So it looks like a trip to the machine shop in the morning to go threw there books.
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That sounds about more like the motor he was talking about. Don't know why I didn't find the gas version when I did my search. He also said he may have one that I can pick up from a friend of his if he still has the old boat. He said something about taking the hole boat, has a busted hull. The wife is looking REAL forward to that one. I guess I can cut it up with a sawsall. I do have a question, are all the blocks the same from the XJs, MJs and YJs? The block that the salvage yard has is like a 1986-1990 vintage, or will I have to use my 1993 block. He was talking about this engine combination (stroker) in the mini sprints that he use to race. when I talk to him again I'll try and get more info.
JR
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he atually ran this in his sprint car with the amc/jeep block?... are you sure he wasn't useing the chevy iron duke 150?
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he atually ran this in his sprint car with the amc/jeep block?... are you sure he wasn't useing the chevy iron duke 150?
This is my concern too...
If we're talking about using the 2.8 to stroke an iron duke, it just goes back to the commercial 3.0 discussion... I do believe they are all the same block.
Oh and it's the pontiac iron duke, just for nit-pickey purposes.
To answer another question; all 86-01/2 blocks should be the same. I do believe they added a girdle and NVH stuff in 97ish, but otherwise they all have the same dimensions...
Now, my own question; in all these pages did anyone take an Iron Duke crank and compare it to the AMC2.5 crank? Or have any other cranks been compared otherwise? If not, let's try, or we're just going back to the offset grinding discussion...
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Ok this is the storey its the 2.8l merc made from 1987 to 1989, its a gas motor and based off the gm iron duke... thats all pretty promising. I cant find the cranks and rod details on line though. So it looks like a trip to the machine shop in the morning to go threw there books.
The Chevy 2.8L is a V6 and not in the same family as the Pontiac 2.5L I4...
If you have a decent engine shop, they should be able to find some pistons and connecting rods that would work though. IIRC, a guy on the mailing list mentioned finding some pistons and forged rods that might work.
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The Chevy 2.8L is a V6 and not in the same family as the Pontiac 2.5L I4...
If you have a decent engine shop, they should be able to find some pistons and connecting rods that would work though. IIRC, a guy on the mailing list mentioned finding some pistons and forged rods that might work.
Is that what we're talking about? The diesel 2.8 I read about earlier is actually a four cylinder, but I don't know about the gas one.
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Bikerjr1 friend is talking about a boat motor that was only used from 86 to 89. They had a 2.5 and a 2.8L but they were not refered to as such. It was a mercury marine 160 or something to that effect and it is a 4cyl. Thats all I know at this point, I'll get this pinned down in the morning when I go to the shop. they have a room the size of a two car garage full of every know tech manual to man. I have a couple other things I need to look at too. I have this week actually, then I'm off the france and Noway for 5 weeks.
I'll do a compare with the iron duke crank to our 2.5 as well.
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Bikerjr1 friend is talking about a boat motor that was only used from 86 to 89. They had a 2.5 and a 2.8L but they were not refered to as such.
Mercruiser used GM engines. The standard were the 2.8L and the 2.5L Iron Duke.
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Mercruiser used GM engines. The standard were the 2.8L and the 2.5L Iron Duke.
yeah, once again we're getting back to that discussion... hopefully littletj97's research will prove something useful, if not from the iron duke, but other four cylinders that could work....
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Its sure sounded nice first thing this morning, but a headache later it does seem to come right back to were this thread started from.
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Just a quick update :'( I've turned over just about every stone and nothing has been found thus far. Starting to think it would have been easier to go .060 over and supercharge it instead. My quick run to the shop the other morning for a morning of research has turned into several days of going threw books. If I dont come up with something today, I'll call off the search.
On another note these 2.5 crank and rods have plenty of beef to take a turbo of supercharger and live a long time. :pot:
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Just a quick update :'( I've turned over just about every stone and nothing has been found thus far. Starting to think it would have been easier to go .060 over and supercharge it instead. My quick run to the shop the other morning for a morning of research has turned into several days of going threw books. If I dont come up with something today, I'll call off the search.
On another note these 2.5 crank and rods have plenty of beef to take a turbo of supercharger and live a long time. :pot:
too bad the crank didn't come forged from the factory like most amc v8's! But yeah, compare pretty much any part of the rotating assembly to a honda four cylinder, everything is like twice the size.
Hm... wish turbo and supercharging was as cost-effective and stock-like as the strokers the 4.0 crowd gets to make!
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Turbo or SC is cost effective IF you do your own work.
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I haven't been able to catch up to my friend to verify some facts we are talking about. He does know that my Jeep is a 1993, it was parked right outside when I talked to him. He said that the only thing that I needed from the other engine was the crank, rods, and flattop pistons. I sure that him being a Jeep/Dodge factory mechanic he knows the differance between the two Jeep motors.
more later when I find out,
JR
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Turbo or SC is cost effective IF you do your own work.
yeah, you're right... I only haven't looked into it because I can't weld, or at least haven't learned yet... my dad knows how, but isn't confident enough to weld anything up like a custom header...
and to bikerjr1, good luck on extracting that information! *crosses fingers*
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Good news.
I talked to him last night. This is the motor we want (2.8L Merc). The crank will bolt in with no clearance problems. There are a couple of choices for the rods and pistons. When I track down my Merc-cruiser engine and start building I'll post every thing I can.
The wife even said I could build the stroker :dance:
Gotta go at work.
JR
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Good news.
I talked to him last night. This is the motor we want (2.8L Merc). The crank will bolt in with no clearance problems. There are a couple of choices for the rods and pistons. When I track down my Merc-cruiser engine and start building I'll post every thing I can.
The wife even said I could build the stroker :dance:
Gotta go at work.
JR
Hmmmm I'm really interested in more info on this crank, and a better spec as to what motor year and such it's comming out of to make it easier to find. This could be a great start at making a monster of a build. :doggy:
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Another friend that I'll be seeing Saturday works as a marine mech. I plan on having him pull the engine specs from their computer or copy the pages that I need from the manual. He doesn't know it yet but he is going to help me find my Merc motor. I'll post them as soon as I can get them. I'm still curious about the 3.0L indust motor that started this. I don't know how hard this Merc engine is going to be to find.
Later all,
JR
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Another friend that I'll be seeing Saturday works as a marine mech. I plan on having him pull the engine specs from their computer or copy the pages that I need from the manual. He doesn't know it yet but he is going to help me find my Merc motor. I'll post them as soon as I can get them. I'm still curious about the 3.0L indust motor that started this. I don't know how hard this Merc engine is going to be to find.
Later all,
JR
I don't think it'll be too hard to find it, the hard part will finding one without a boat attached to it...
I'm still skeptical, but once you post some numbers and proper comparisons I'll have more confidence in this option!
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If I do find one with a boat, well, that's no problem. I have a SawsAll, beer cooler,and a big trash bin that will take care of the boat. I'll probablly have some help too, how many times do you get to cut up a boat. It will be a big trash day.
later,
JR
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If I do find one with a boat, well, that's no problem. I have a SawsAll, beer cooler,and a big trash bin that will take care of the boat. I'll probablly have some help too, how many times do you get to cut up a boat. It will be a big trash day.
later,
JR
If it is a fiberglass boat, I recomend you cover yourself as best as possible; fiberglass on your skin itches like hell!
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If it is a fiberglass boat, I recomend you cover yourself as best as possible; fiberglass on your skin itches like hell!
I know exactly how it feels, ever retrofitted houses for surround sound and satellite? running wires through insulation-filled attics really kills...
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I know that a stroker has been brought up before :twofingers: and is always shot down but hell why not do one. If I were to do it, the goal displacement would be 3.0l and build it to be turbocharged. :pot: Im just wondering if there is anyone who knows what it would take to do this and what kind of numbers this sucker could put out. Just trying to start a discussion and maybe inspire some people to push the limits on the little motor that can.
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Another friend that I'll be seeing Saturday works as a marine mech. I plan on having him pull the engine specs from their computer or copy the pages that I need from the manual. He doesn't know it yet but he is going to help me find my Merc motor. I'll post them as soon as I can get them. I'm still curious about the 3.0L indust motor that started this. I don't know how hard this Merc engine is going to be to find.
Later all,
JR
The 3.0L Merc is the most common boat engine on earth. If you are looking for one to screw around with, you can get them cheap since they are pretty much un-rebuildable (Cannot be bored out). My last couple boats have had 3.0L in them, good motor but they are all carburated.
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One other thing I should mention is that there are basically no performance mods available for the 3.0L even though it has been in use for 20 plus years. The reason is that the motor tends to self destruct if you get much over the stock 135 HP rating.
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Well I was checking out a later FSM today, just looking at specs for the VM Motori 2.5TD, while it has a longer stroke than our 2.5's, I think the crank is just too short. Not that it matters too much, because it's europe-only...
But anyways, I was surprised to learn the VM is actually an OHV, two valves per cylinder, driver-side drought engine. Roller lifters unlike our engines, but it's still pretty interesting. I wish the crank and connecting rods were interchangeable, they pretty much have to be forged because of the high CR, I'm still looking into it but I doubt I'll find anything...
I'd like to know what progress bikerjr1 has had too, if possible?
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another old thread brought back to life/ nice to see people still looking for more options/ if we get a solid answer on fitment maybe my monster will come out and get that last bit of push to cap off my engine build
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It will probably be another week or so before I can get the specs. My friend has to download them at work and burn them then I have to catch him when I'm in town. Hopefully it will have some useful info. Still no luck finding a 2.8L Merc motor to tear apart. The search goes on....
JR
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I'm out of town untill late may, In Luxembourg at the moment. Hopefully someone can source info while i am gone. if not I will continue on the quest when I return. I know we could get cranks made to our spec, and it would be cheaper if several of us was serious about the project. I know people at crower cams they have the ability to custom make any crank shaft, but one off's are costly.
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Extremely intresting stuff here!
Read the whole thread from start to here and gotta know did anyone ever figure out if the crank from
the 2.8l merc work?????
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Extremely intresting stuff here!
Read the whole thread from start to here and gotta know did anyone ever figure out if the crank from
the 2.8l merc work?????
i remember going thru this also and didn't find a definite answer - dwtaylor mentioned in another thread that he knows somebody that was running a 3.0L stroker (if i remember correctly but not sure) but i don't know if that was the pre-chrysler motor (whatever was used in Pontiac & such) or the one we all have - maybe he can clarify that and if he's got more info i'd be really interested to hear.
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The 3.0 stroker was a custom SCAT crankshaft. I called them a year or so back when I was doing my rebuild to see if they would still build one. 4500 bucks was a bit high for me :yikes: .... Di-spite the potential of a forged billet balanced crank... :hump:
Dave
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The 3.0 stroker was a custom SCAT crankshaft. I called them a year or so back when I was doing my rebuild to see if they would still build one. 4500 bucks was a bit high for me :yikes: .... Di-spite the potential of a forged billet balanced crank... :hump:
Dave
awhmmm, yeah - way too much.
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the only place ive read of doing a 2.5l to 3.0l stoker was with the iron duke 2.5l using the 2.8l merc crank (as far as one where they actually did it)..
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The 3.0 stroker was a custom SCAT crankshaft. I called them a year or so back when I was doing my rebuild to see if they would still build one. 4500 bucks was a bit high for me :yikes: .... Di-spite the potential of a forged billet balanced crank... :hump:
Dave
wow.... for that price I would HAVE to look into a new motor... that is really discouraging....
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For 4500 I can almost drop a corvette engine in there....
Yea I was kinda surprised, especially since SCAT supposedly had built them before, it was for the SCORE and ARCA desert racing in the early 90's.
Dave