Hi all. I joined the forum to research the possibility of doing a stroker on the 2.5L engine. I can only find two references on the forum to someone who has done an actual stroker:
Rex Lair's 2.7L stroker, and
someone's 3.0L stroker.
Here is what Rex had to say about his 2.7L stroker on the yahoo group:
The head has been ported with bigger intake and exh. valves.
The engine is actually board 30 over. It has a custom crankshaft and I beam rods. If you do the math you will find out that boring your engine 60 over we'll give you a 2.55L. There's not enough room to move the rod journal out any further without serious modifications to the block itself. The rods would hit the inside of the block. The crankshaft, rods and pistons are all custom made. I have well over $5,000.00 invested into the bottom end of this engine.
This motor ran good with the stock port injection system. I just needed to get more air fuel into the motor. The stroked crankshaft was made by Ohio Crankshaft; they also provided the rods and the pistons. There's definitely a noticeable difference between the 2.5 and the 2.7. There are no dyno tests I'm sorry to say. The motor was originally built for the sportsman class jeepspeed off road series. It was the only four cylinder running with all the 4.0L six cylinder. Jeepspeed combined the pro class and the sportsman class. In the roughest part of the race tracks the 4 cylinder had no problem keeping up with the six cylinders. On the long straight aways the 4 cylinder just could not keep up with the six cylinders. The truck consistently came in third or fourth out of 20 to 30 Jeepspeed Cherokees. Go to www.jeepspeed.com and check out the jeeps. The head is the heart of the motor; I had all sorts of porting done with the use of a flow bench till we got it right. I ran a 600 cfm Holley projection fuel injection system and the jeep would only get about 4 miles a gallon. The motor could turn about 8000rpms the power band came on about 2100rpms and never stop. We would run the motor up to 6200rmps and then shift gears.
I contacted
Ohio Crankshaft and asked them if they remembered Rex's setup. They told me that they have only ever done a few offset grinds. So it would appear that Rex's 2.7L is an offset grind with custom rods and pistons.
Then according to
dwtaylorpdx's post a 3.0L stroker was done with a custom billet crank from Scat. Dave, do you have any more information on this build? Rex seemed to be of the opinion that a 3.0L can't be done without considerable work on the block... Anyone measured the width of a 2.5 vs. a 4.0? Considering all that is shared between the two engines I'd be surprised if the 2.5 couldn't take a stroke of at least 3.670" (Stock 4.0 stroke is 3.413", stock 4.2 stroke is 3.895" so .482" in stroke is gained in a 4.0 stoker. Adding the same .482" to the stock stroke of a 2.5, 3.188" is how I got 3.670"). But that would yield slightly less than a 2.9L displacement with a +.030 bore.
I found this
thread on Pirate4x4 where Martin(jpfrk2001) is planning a build of a '93 2.5 from a YJ that he claims will make 220HP and 300TQ naturally aspirated. But, he doesn't share any of the build details on how to get there. I don't see how this is possible without stroking his 2.5.
The only other source I can find is from
505 Performance. But, based on the opinion of them from other boards, and their
tendency of not providing details, I would only consider their products for a race engine that isn't designed for a long life.
Finally I contacted
Scat Crankshafts to see if their price had changed for the billet crank (answer: no). So it would appear that there is currently no good economical way of stroking the 2.5. Out of curiosity I asked what it would take to get a 2.5L stroker crank to be a standard part like the 4.0L stroker crank. They said they would need 150 orders to make it worth their while to invest in the tooling.
The 4.0L stroker crank is $399 from Scat, so I would expect the 2.5L to be less. With the swapability between the 4.0 and 2.5 we would then have all the same options as a 4.0 stroker, and at a reasonable cost. Is this something people would be interested enough in to put their money where their mouths are?
Rob
