Topic: 98' TJ 2.5 Rebuild Questions

[JeepLess]

  I plan on getting a 2.5 block and rebuilding it for my 98' TJ.......because I want a back-up AND to keep me busy for a bit. What I would like to know is what others have done with their rebuilds and their findings. I'm looking for info on bore / cam size and any other mods that would be beneficial.

Thanks in advance!

P.S. I did a search and didn't really find the info I was looking for.........I'd welcome links to point me in the right direction too!

[sharpxmen]

  I plan on getting a 2.5 block and rebuilding it for my 98' TJ.......because I want a back-up AND to keep me busy for a bit. What I would like to know is what others have done with their rebuilds and their findings. I'm looking for info on bore / cam size and any other mods that would be beneficial.

Thanks in advance!

P.S. I did a search and didn't really find the info I was looking for.........I'd welcome links to point me in the right direction too!

projects section maybe...

[TexWalther]

This project is actually one of the reasons i joined this site. http://4bangerjp.com/forums/index.php/topic,6007.0.html guy was getting right around 200 on both HP and torque. had around 1500 invested which wasnt very bad for a rebuild

[sharpxmen]

This project is actually one of the reasons i joined this site. http://4bangerjp.com/forums/index.php/topic,6007.0.html guy was getting right around 200 on both HP and torque. had around 1500 invested which wasnt very bad for a rebuild

keep in mind that you can build the engine to whatever specs you want but you won't make more power unless you add more fuel - the Jeep PCM would reach a limit at some point - 200HP with the same amount of fuel flow as for 120HP won't be possible (I also doubt you will get 200HP at the same top rpm as stock, seems a bit of a stretch but to be honest I can't tell you for sure is not possible, just fyi to manage your expectations, 50 HP increase would be a more realistic goal with a hi-perf build based on Mopar numbers for competition cams).

[Jeffy]

Supposedly Mopar Performance was getting 215-230HP from the 2.5L's when they were doing the Craftsman Truck Series.  Although these were race trucks that get torn down after every race.  Service intervals probably weren't that great.  Also, the parts were originally designed to be used with the OBD-I era engines.

Realistically 150-175Hp would be more then adequate.  Especially if you get raise the Torque.  Torque is what the 2.5L really lacks.  If it had 190-200ft-lbs, no one would be complaining.

[FourbangerYJ]

Realistically 150-175Hp would be more then adequate.  Especially if you get raise the Torque.  Torque is what the 2.5L really lacks.  If it had 190-200ft-lbs, no one would be complaining.

The AX5 would! 

[Jeffy]

The AX5 would! 

Build it up as well.  I'm still curious about Marlin's W56's...

[FourbangerYJ]

Build it up as well.  I'm still curious about Marlin's W56's...

I don't see why it wouldn't work. I don't know of anyone running one. But knowing Marlin he knows how to make it work.
Find a pass. drop D44 and run Toyota boxes.  Or use their lefty and keep the D30.

[FourbangerYJ]

We are getting off  topic here but there is info here on Toyota trannies behind the 2.5L

http://board.marlincrawler.com/index.php?topic=5449.0

[sharpxmen]

Supposedly Mopar Performance was getting 215-230HP from the 2.5L's when they were doing the Craftsman Truck Series.  Although these were race trucks that get torn down after every race.  Service intervals probably weren't that great.  Also, the parts were originally designed to be used with the OBD-I era engines.

Realistically 150-175Hp would be more then adequate.  Especially if you get raise the Torque.  Torque is what the 2.5L really lacks.  If it had 190-200ft-lbs, no one would be complaining.

probably 8000rpm (if not more) - i think they were rpm limited but don't know what was at, maybe 9000

not to mention forged pistons, not pump fuel, who knows what CR and possibly crank and connecting rods

idle probably at 1500 or even higher, and like you said rebuild the engine every race.

a set of custom forged pistons for the 4 banger would take you about $500

my statement about mopar was to the numbers over stock they claimed out of the performance cams (and that included roller rockers and springs and i think also longer valves but can't be sure).

you can get a torque cam for the 4 banger though but would lack top end

[TexWalther]

agree that 200 hp would be a little much to expect, but he was looking for information on a performance build and this was the best i found having searched through many different forums

[sharpxmen]

agree that 200 hp would be a little much to expect, but he was looking for information on a performance build and this was the best i found having searched through many different forums

the limitation for power would be the rpm (if you keep all the major components the same) - think about it this way:

stock is 120HP and i think it was 125 for the ones on the Cherokee so we can start with that as a base. Your power is given by the amount of fuel you can burn and that's a direct relation to the air that the engine "inhales" per cycle. A better cam would give you better VE (volumetric efficiency) at high rpm so there's more air and you can burn more fuel. More rpms mean more air in the unit of time (more engine cycles in the same given amount of time). At the same rpm you would only increase the power by increasing VE and adding more fuel, not sure what the VE for the 2.5 is but I calculated it at some point and it was something between 70 and 80, even with it at 70 the best you're going to get (but very unlikely) is 30% increase, so that makes it about 40HP. so to get 80HP increase you'd need more rpm or forced induction - this is all a quick approximation but just to give you an idea.