86 chomanche upgrade Posted May 26, 2015 Share Posted May 26, 2015 I got the 2.5 n a 86 I wanna run 33s is a 2.5 worth rebuilding and can I put a cam n it or stroke it for more power Link to comment Share on other sites More sharing options...
87Warrior Posted May 26, 2015 Share Posted May 26, 2015 Yes. Checkout JeepDriver and MnkyBoy build threads. Link to comment Share on other sites More sharing options...
outlaw star Posted May 27, 2015 Share Posted May 27, 2015 I'm building a 2.9L stroker for mine as well. Link to comment Share on other sites More sharing options...
mnkyboy Posted May 27, 2015 Share Posted May 27, 2015 My 2.5l when it was still TBI turned 33s pretty well with just a regear to 4.88s. Revolution gear recently released 5.13s for the stock axles so you could go even deeper. Link to comment Share on other sites More sharing options...
johnj92131 Posted May 27, 2015 Share Posted May 27, 2015 I'm building a 2.9L stroker for mine as well. What are you doing to the crank to stroke it to 2.9 l?? That is a big increase in displacement. Link to comment Share on other sites More sharing options...
Eagle Posted May 27, 2015 Share Posted May 27, 2015 I'm building a 2.9L stroker for mine as well. What are you using for the stroker crankshaft? Link to comment Share on other sites More sharing options...
outlaw star Posted May 27, 2015 Share Posted May 27, 2015 Using custom pistons, rods and crank. Displacement = Bore (stock) x Bore (new) x stroke (crank/rod) Stroke can be achieved by either a new crank offset and rod length. Link to comment Share on other sites More sharing options...
jimoshel Posted May 27, 2015 Share Posted May 27, 2015 Curious as to how you can increase stroke with a longer rod. The piston is going to travel the same distance in the bore depending on the stroke. Not rod length. Or is this the new math they're teaching in schools now? Link to comment Share on other sites More sharing options...
outlaw star Posted May 27, 2015 Share Posted May 27, 2015 Sorry, still medicated, my mistake. I meant the stroke of the crank not rods. You can change the rod length to aid as well. The SD4 (Super Duty 4) Pontiac Fiero crank will work in our 2.5L but was available in in five different strokes. 2.6", 3.00", 3.25", 3.625" and 3.937" (don't attempt to use this one as it was a race only crank that will push the pistons too far into the combustion chamber!) With this Crank, Use SBC 6.00" w/ Large journal 2.1" x .955" rods. (With this measurement you can find custom rods easy like Manley or Eagle. Link to comment Share on other sites More sharing options...
outlaw star Posted May 27, 2015 Share Posted May 27, 2015 On the 3.25" & 3.625" cranks, if you do not use at least a 6.00" rod, you risk the chance of pulling the piston out of its bore (more or less the rings) on BDC. I've got a whole notebook on all my math and research but its a lot to type. I'm using custom 3.960" bore pistons and a 3.25" stroke crank. Final math is 2.926402 (2.9L) Link to comment Share on other sites More sharing options...
outlaw star Posted May 27, 2015 Share Posted May 27, 2015 If you source a SD4 crank w/3.25" stroke and bore your 2.5L .060 over, you end up at 158.09cid 2.59 (2.6)L The 3.960" pistons can be bought through 505performance or made by any good company like Ross, JE or Keith Black. I had a SD4/Marine crank already. If you get a SD4 Pontiac crank you will have the hole for harmonic balancer already. But if you source a marine crank like I did, you will have to drill and tap for the balancer bolt. Link to comment Share on other sites More sharing options...
jimoshel Posted May 28, 2015 Share Posted May 28, 2015 I once installed a set of rubber connecting rods in a souped up engine. When the piston hit the cylinder head the rubber would give, saving the head and piston from damage. Link to comment Share on other sites More sharing options...
outlaw star Posted May 28, 2015 Share Posted May 28, 2015 I once installed a set of rubber connecting rods in a souped up engine. When the piston hit the cylinder head the rubber would give, saving the head and piston from damage.Lmao. Link to comment Share on other sites More sharing options...
johnj92131 Posted May 28, 2015 Share Posted May 28, 2015 On the 3.25" & 3.625" cranks, if you do not use at least a 6.00" rod, you risk the chance of pulling the piston out of its bore (more or less the rings) on BDC. I've got a whole notebook on all my math and research but its a lot to type. I'm using custom 3.960" bore pistons and a 3.25" stroke crank. Final math is 2.926402 (2.9L) If you source a SD4 crank w/3.25" stroke and bore your 2.5L .060 over, you end up at 158.09cid 2.59 (2.6)L The 3.960" pistons can be bought through 505performance or made by any good company like Ross, JE or Keith Black. I had a SD4/Marine crank already. If you get a SD4 Pontiac crank you will have the hole for harmonic balancer already. But if you source a marine crank like I did, you will have to drill and tap for the balancer bolt. Outlaw star: You want to check your math for 2.9L. If a .060 over bore and a 3.25 stroke equals 158 cu. in. then an .080 overbore to 3.96 equals 160 cu. in. with 3.25 stroke. Now, with a 3.625 stroke and a .080 you get 178 cu. in. or 2.92L Good find on that SD4 crank. Does it just drop in? Now that SD4 engine could be interesting at 3.3 litres and with the 4 valve head. Link to comment Share on other sites More sharing options...
outlaw star Posted May 28, 2015 Share Posted May 28, 2015 You're right, Thanks. Used the wrong crank number. .060 Over bore = 3.94" x 3.625 stroke crank = 176.787cid/2.897L (2.9L). Think I used my Chevy Marine notes instead of the AMC notes. Lol. Link to comment Share on other sites More sharing options...
outlaw star Posted May 28, 2015 Share Posted May 28, 2015 Damn pics didn't load last post.. Here's the math conversions. Link to comment Share on other sites More sharing options...
outlaw star Posted May 28, 2015 Share Posted May 28, 2015 Now that I'm awake and non-medicated, I just read over my first few posts. All I can say is building/designing an engine is a lot like being on a date with a really hot girl. Because one unexpected period will screw the whole thing up. Link to comment Share on other sites More sharing options...
jimoshel Posted May 28, 2015 Share Posted May 28, 2015 You're gonna be OK... Link to comment Share on other sites More sharing options...
64 Cheyenne Posted May 28, 2015 Share Posted May 28, 2015 You're gonna be OK... Thats what she said... Link to comment Share on other sites More sharing options...
outlaw star Posted May 28, 2015 Share Posted May 28, 2015 You're gonna be OK...I'm trying. This damn Heart meds and pain meds they got me on are really getting to me... But thanks for the laugh. Link to comment Share on other sites More sharing options...
dasbulliwagen Posted May 28, 2015 Share Posted May 28, 2015 Are you sure a GM crank will go right into an AMC block? Some people get the pre 84 GM 2.5 mixed up with the 84 and later AMC 2.5. I just want to clarify this. I don't want to get excited over nothing. I've done some preliminary research on the AMC 2.5 and have never seen this mod mentioned. On www.4bangerjp.com I've never seen this mentioned. And if it would be mentioned anywhere it would be there. Link to comment Share on other sites More sharing options...
outlaw star Posted May 28, 2015 Share Posted May 28, 2015 I'm using the OMC version. I've measured and mic'ed it. The caps will have to be line bored/machined a little along with the flywheel flange. There are also two different styles, 1 piece rear main and two piece rear main. I'm using a one piece. Link to comment Share on other sites More sharing options...
outlaw star Posted May 28, 2015 Share Posted May 28, 2015 AMC/Chrysler used to own OMC and manufactured the Mercruiser before Chevrolet bought them out around 89-90. Link to comment Share on other sites More sharing options...
outlaw star Posted May 28, 2015 Share Posted May 28, 2015 Are you sure a GM crank will go right into an AMC block? Some people get the pre 84 GM 2.5 mixed up with the 84 and later AMC 2.5. I just want to clarify this. I don't want to get excited over nothing. I've done some preliminary research on the AMC 2.5 and have never seen this mod mentioned. On www.4bangerjp.com I've never seen this mentioned. And if it would be mentioned anywhere it would be there.I tried to register there (4bj) just to look around but I couldn't for some reason. I have seen it on fb but looks like only Wranglers there which I don't really care for. Link to comment Share on other sites More sharing options...
mnkyboy Posted May 29, 2015 Share Posted May 29, 2015 Alot of us with 2.5l's are on there,you can't just join the forum,you have to Message Jeff on Facebook and he will add you to the forum. Kind of a pain but it makes for a very problem free forum since you have to go out of your way to be there. Link to comment Share on other sites More sharing options...
Recommended Posts
Create an account or sign in to comment
You need to be a member in order to leave a comment
Create an account
Sign up for a new account in our community. It's easy!
Register a new accountSign in
Already have an account? Sign in here.
Sign In Now