Topic: Getting more out of your 4 squirrels

[Wrench]

On my setup, I found the Felpro gasket to be somewhere in the 0.060" thickness range, and the Victor was in the 0.070" range.  In order to get a usefull squish clearance of under 0.040", I had to deck the block nearly 0.070" to get in the 0.030" squish range with the Felpro gasket.

There is a Jeep 4.0 piston that has a larger compression height that is a direct fit, but it still doesnt get you close enough.  If you could find a source for the Jeep 2.5 steel shim gasket (0.020") that I found on my 1986 spare engine, you could get it within range without decking the block.  I have searched high and low and cannot seem to find where that head gasket came from.

[sharpxmen]

If you could find a source for the Jeep 2.5 steel shim gasket (0.020") that I found on my 1986 spare engine, you could get it within range without decking the block.  I have searched high and low and cannot seem to find where that head gasket came from.

that was a Mopar branded performance gasket, i think it was made by Victor - not available anymore from what i remember.

[Wrench]

I just picked up a '92 Wrangler with 130k miles on it (has a very clean/stock MPI engine in it).  I plan to swap my upgrades one by one of the XJ and hope to get some dyno time to document the actual improvements.

[dwtaylorpdx]

Just a sidenote on the gaskets, The Victor gaskets are pretty notorious for failure if used in a engine run very hard in other engine, Mine were felpro and have held up well, so strictly from watching others re-head their BMW's..

On my build the builder did some light port work on the valve guide, he shortened the guide and a light grind on the head material around it to provide a more tear drop shape than round, and a 5 cut grind on the seats/valves. He commented several times about how big the ports on my 95 head are. (He was a motor man on a Winston cup crew for  a few years. ) He mentioned that overall the 2.5 isn't too bad and thought a longer intake runner was probably what it was missing, thought it would pull better torque and still get good rpm with the fairly healthy port and runner size, might also pick up mileage a bit.

I have the Hesco grind clay smith cam.

Something else to check on the intakes some have a flow splitter below the throttle body some don't. The one with the splitter makes better pulling torque near as I can tell on my commute, pulls better at cruise and doesn't fall off power quite as quick. (Mine is MPFI)
My original plan was to cut two and weld them together to see if I could get some runner length.. But so far life is conspiring to steal my fun..



 

[dwtaylorpdx]

The stroker kit from 505 performance for the 2.5 is 1700 bucks..
Not that bad if you consider the cost of machining the original crank and that it comes with cam and valvesprings..

My last build the parts were about a grand as I recall. Machine work and assembly 800.



 

[Wrench]

I looked into the 505 kit, but I remember hearing about reliability issues.  The factory stroke/bore ratio on this engine is actually pretty good, but the HP per cubic inch and economy are not so good in stock form.

I have a lot of respect for the Chevy LS engine design, so I have been doing a lot of comparing between the two. 
-The 5.3 intake has a runner length of 10.3", and I believe the combined total length including the head is around 14-15".  The 2.5 combined port length is nearly the same. I suspect there is little to gain with longer runners.
-The 5.3 intake runner volume is 0.54 liters, and total manifold volume is 5.2 liters.  The 2.5 Jeep manifold has no taper to the runners like the LS, and it has virtually no plenum (which I believe is why the larger TB and TB spacer are reported to work well on this engine).  I believe tapered runners and a larger plenum may really help.

I agree with your assessment of the Victor gaskets.  I blew one and switched to Felpro.

I now have 3 complete 2.5 engines on hand and two MPI intakes to play with.

I took the YJ out the other day for a test run.  It pulls better below 2k rpm than my carbureted one, but by 3500 there is no comparison.  It definitely needs some work.

[dwtaylorpdx]

I've been considering the runners because the 2.5 Neon ACR's have a dual path intake, and the short runners are the same length as the 2.5 Jeep, the longer runner path is about 6" longer. Haven't done much other research yet.. My fundemental plan is a new EFI controller and ditch the POS jeep one. Hoping the bonuses are UP this spring.. :D

[Jeffy]

Might as well ditch the Jeeps ECU and run a programmable/logging unit.

[Wrench]

Might as well ditch the Jeeps ECU and run a programmable/logging unit.

Mega Squirt is at the top of my list.

I think that may be the key for those running fuel injection and wanting the most out of the engine.  My carbureted version has no limits to tunability, and I used a Summit digital box for a rev limiter.  I havent checked to see what the '92 has for a limiter, but if it kicks in at 5200 like some of them, that can really put a damper on the potential of this engine.  Seriously, the stock ports are large enough to support ~7000 rpm.  I dont know the actual peak limit of the crank and rods, though.

The valve train is a massive limit to rpm.  I am curious to see if the Chevy LSx lighter vavles/retainers/beehive springs can be adapted to this engine to help.  The stock valve train is much too heavy and under-sprung to go over 5k rpm with the stock cam, and gets much worse when you get a real cam in there with decent lift.

[h20pumper]

add a Turbo

it spins

https://www.youtube.com/watch?v=M3dl5gFPaGc&list=UUpmMtyWMsI2KXWlHf5zQQIQ

[sharpxmen]

Mega Squirt is at the top of my list.

I think that may be the key for those running fuel injection and wanting the most out of the engine.  My carbureted version has no limits to tunability, and I used a Summit digital box for a rev limiter.  I havent checked to see what the '92 has for a limiter, but if it kicks in at 5200 like some of them, that can really put a damper on the potential of this engine.  Seriously, the stock ports are large enough to support ~7000 rpm.  I dont know the actual peak limit of the crank and rods, though.

The valve train is a massive limit to rpm.  I am curious to see if the Chevy LSx lighter vavles/retainers/beehive springs can be adapted to this engine to help.  The stock valve train is much too heavy and under-sprung to go over 5k rpm with the stock cam, and gets much worse when you get a real cam in there with decent lift.

I wouldn't spin this particular engine over the factory redline, it is just not designed for that (I mean you can get it if you want to spend the money but not worth it as in the end you're better doing a swap).

[Wrench]

My '84 engine has had the rev limiter set at 5500 for 4 years now, frequently bouncing off the limiter.  That is with the stock cam advanced 4 degrees and "de-ported" head (both of which are supposed to lower the effective rpm range).  The only issue I have had is the valve train; floated valves and nearly lost the stem locks on one valve (stock springs).

The two things that I have found on this engine in stock form that make it run flat before redline are 1) valve float and 2) squish clearance way too loose (stock ~0.080").   

In order to get the squish to work for you on pump gas, you will need to open the combustion chamber or use pistons with a larger dish.

I didnt mean to imply anyone run this engine to 7k.  6k is a reasonable goal for this engine to handle, and can bump the peak potential quite a bit over stock.

[sharpxmen]

My '84 engine has had the rev limiter set at 5500 for 4 years now, frequently bouncing off the limiter.  That is with the stock cam advanced 4 degrees and "de-ported" head (both of which are supposed to lower the effective rpm range).  The only issue I have had is the valve train; floated valves and nearly lost the stem locks on one valve (stock springs).

The two things that I have found on this engine in stock form that make it run flat before redline are 1) valve float and 2) squish clearance way too loose (stock ~0.080").   

In order to get the squish to work for you on pump gas, you will need to open the combustion chamber or use pistons with a larger dish.

I didnt mean to imply anyone run this engine to 7k.  6k is a reasonable goal for this engine to handle, and can bump the peak potential quite a bit over stock.

your power drops off past the peak, so really don't see the point. You're better off getting some other mods (6 speed and axle gearing would do a lot more than 500 rpm as it would keep it in the power band better which is the only reason to go higher in rpm anyway). Not to mention the added mechanical stress.