rebuilding engine

[nitroxsteve]

I plan to pull my engine this weekend and rebuild it. I'm planning to go back mostly stock but was wondering if anyone has any ideas on adding a little better performance. What Cams Are you running? by the way its a 88 4.0 5speed.

 

Thanks

[jimoshel]

When I rebuilt my 2.5 I took a good look at the camshaft. It just seemed like to me all those bumps required horsepower to make the lifters ride up and over the bumps. Took my grinder and smoothed all the bumps until the shaft was perfectly round. It worked. After assembling the engine ,I could rotate it with just hand. Now if I can just figure out why it won't start. :dunno: :thwak:

[nitroxsteve]

When I rebuilt my 2.5 I took a good look at the camshaft. It just seemed like to me all those bumps required horsepower to make the lifters ride up and over the bumps. Took my grinder and smoothed all the bumps until the shaft was perfectly round. It worked. After assembling the engine ,I could rotate it with just hand. Now if I can just figure out why it won't start. :dunno: :thwak:

 

Sucks you can't get it to run but when you figure it out you will probably need some high speed bumper bolts and chrome foot gas pedal just to keep it under controll.

[mnkyboy]

When I rebuilt my 2.5 I took a good look at the camshaft. It just seemed like to me all those bumps required horsepower to make the lifters ride up and over the bumps. Took my grinder and smoothed all the bumps until the shaft was perfectly round. It worked. After assembling the engine ,I could rotate it with just hand. Now if I can just figure out why it won't start. :dunno: :thwak:

 

 

You can also try cutting the cam in half making it a twin cam :thumbsup:

[4X4COMANCHE]

you guys are brutal

[64 Cheyenne]

Now how about some serious input.

 

I'd like to follow this thread if it was serious, I'm in the beginning of an engine build myself and would like any serious input.

 

92 HO motor for HO conversion in the 87.

[jimoshel]

The HO engines are so well designed and built that there is really very little can be done to improve their performance without going to 'big bucks' outlay. Because of the small market not to many manufacturers make parts for them. A couple years back Crower listed 2 cams for the 4.0 but nothing for the 2.5. There are headers being advertised on EBay but I don't see where they would be that much improvement, just looking at them. They don't give any performance specifications on them. IMHO the best single thing that can be done to these engines is blueprint them. Time consuming but cheap and effective. Again, IMHO the one single improvement to be made is turbo charging, with more noticeable gains inland and at altitude, than along the coastal areas. You can have a cam reground at any machine shop but the disadvantage here, or advantage, depending on your point of view, is your moving, and, or narrowing your torque curve. There is also the option of milling the head for a point or two compression ratio. Have to be more selective with your choices of gasoline with that route. The old standby, headers and dual exhaust don't really gain that much with these engines. For just every day driving and reliability you're just not gonna beat the stock engine. If your building a full out race, competition machine you need big bucks, a trained, knowledgeable staff and limitless resources. If you have all that then your not going to be in CC asking for advice.

[johnj92131]

A turbocharger will help a bunch. A low bucks stroker with dished out pistons will help the low end power. A smaller turbo would be better than a large/huge turbo.

 

If you have to rebuild the engine - your first choice should be a stroker crank.

[87Warrior]

Head over to JeepStrokers. You can learn a lot just by understanding what parts are out there for the 4.0. I have done a lot of research over there for engine advise and I am not doing a stroker. I selected the 321 cam as it is highly recomended by the stroker crew for a higher output 4.0.

 

My plan:

Comp Cam 321

Sealed Power Pistons 0.030 over

Zero Deck cleanance

0.052 Quench with factory size head gasket

 

The Sealed Power pistons are a little shorter than stock with a larger dish. (they are as close to factory as you can get) This is why I am opting for 0.00" deck clearance. It should yeild a static compession ratio of about 9.7:1 (just a shade over stock, not really important) and a dynamic compession ratio of 8.9:1. (going from memory, my CR numbers may be wrong) Should be able to run it on pump gas without issue.