98 Grand Stroker with no power

[Evanchek]

Hi guys, I am new to this forum but am need of desparate help. I have a 98 Grand Cherokee which we pulled the 4.0L and did the following mods:

New Engine Parts Installed:

Icon forged pistons IC944-060
Skat 9000 crank
Ibeam forged rods
Moly piston rings
Comp Cam 68-232-4
New timing set & lifters
New freeze plugs
High volume oil pump
Harland Sharp rockers on head
New exhaust and intake valves
New valve springs
Banks torque tube header

Machine work Included:

Boring and honing block .060
0 Deck the block
Mill & Port the head

With the engine completely assembled the final compression ratio we got was almost exactly 10:1. We reinstalled the motor and put FMS 24lb injectors and connected everything back as if it was stock in the grand. We used the factory distributor with autolite plugs, and stock coil as well. Fired the engine up and broke cam in per procedure and everything seemed to be good (minus not having a tranny cooler line hooked up first go around so spewed tranny fluid all over my garage for about 10 seconds ). Good idle, smooth running (no pings, knocks, or misses). Also should have mentioned the tranny was rebuilt with a high stall torque converter as well. Went out for a test run and there seemed to be VERY LITTLE OR NO CHANGE IN THE PERFORMANCE!!! Not sure what was going on we have tried a few things. Changed fuel pump and measured fuel pressure at rail (49 PSI as per stock I believe). Put new air filter setup on it (K & N I believe). Still the vehicle seems to just drive like a basic grand cherokee 4.0L. It seems like it has good acceleration power from about 0-20 mph on the road and then seems to lack from there up. Not sure if that is just me or not, it just seemed like it when I drove it. We are still at a loss as to what we should do next. We have a scheduled dyno appointment for it friday morning which is what the tech guys told us to do when we called them about this. They said it might be that the computer is not able to adapt to the new performance mods. I know it has an OBD2 computer in it, which I thought would not be a problem and we wouldn't have to make any changes to it? Am I wrong there? Do we need to have it re-flashed or run a chip? If so who can reflash it or what performance chip should we run? Is there anything else we should look at?

All in all we know it should be doing MUCH better than it does. It has been pretty disappointing over the last month or so. Also we have broken the motor in. It has about 740 miles on it now or maybe more. Wanted to make sure new valves and other components got well seated before dyno test. PLEASE ANY HELP WOULD BE APPRECIATED!! Our team has never done a rebuild like this and we are just looking for some insight. Thanks!

[Cheromaniac]

At 740 miles the engine's still going to be pretty tight so don't expect a massive performance boost from the outset. There's nothing radical about your stroker so the OBD 2 engine management system should have no problem adapting to it. I suggest you wait until you've passed the 5000 mile mark before you dyno test it çause by then the engine should be nicely loosened up.

[SilverXJ]

Try to reindex the distributor. I doubt thats the problem, but worth trying.

Check the MAP TPS and O2 sensors. Do you have a wideband?

What injectors are you running?

Was the cam degreed in and what timing set are yo using?

[Evanchek]

Haven't checked the MAP TPS yet. We will look at that tonight. Dont have wideband. Running Accel 150824 injectors (24lb). Have to see about the cam being degreed in. I think the timing set was bought as a kit from summit racing with the cam (SK68-232-4 I think is the number).

[dwg86]

I will agree with silver on checking the cam indexing(degreeing).

[superstingray77]

did you ever find the culprit?
how much stall did you put in it? If its way too loose the added tq of the striker will just be wasted, ie a 4000+rpm stall will just start to transfer power 1500 rpm before the engine runs out of steam. 2200 stall and proper line pressure set in tv cable so trans doesn't slip it should move well, unless timing and afr are way off.

[superstingray77]

did you ever find the culprit?
how much stall did you put in it? If its way too loose the added tq of the stroker will just be wasted, ie a 4000+rpm stall will just start to transfer power 1500 rpm before the engine runs out of steam. 2200 stall and proper line pressure set in tv cable so trans doesn't slip it should move well, unless timing and afr are way off.