balance questions and then some

[Zorm]

OK, the inital question is, did a 258 ever have a serp belt set up. #2) since the 258 is externally balanced and the 4.0 internally, what would I need to do to put a 4.0 serp set up on my 258 with the 4.0 head and soon the 2000 4.0 MPFI?
I am thinking if I can find a 258 that had a serp belt, try and find that harmonic balancer then have the 4.0 fly wheel balanced the same as the 4.2 flywheel.

OR can anyone of the stroker pros tell me what the difference is between having the 258 but with a 4.0 head and fuel system/ over the 4.0 package with the 258 crank and rod arms?
would not both engines be the same?

thanks for any input

[Missourian]

OK, the initial question is, did a 258 ever have a serpentine belt set up.

In short YES, from 1987 to 1990 in the Jeep Wrangler.

#2) since the 258 is externally balanced and the 4.0 internally, what would I need to do to put a 4.0 serpentine set up on my 258 with the 4.0 head and soon the 2000 4.0 MPFI?

What makes you believe that one is and the other isn't internally balanced? You see, both are internally balanced just having varying weights to accomplish the task.

[amcinstaller]

what he said, also the 258 was treated to serpentine setups even earlier in amc eagles. both are intenal balance, and the head swap wont net you as much of a gain as the stroker. my best guess would be likely because of the bore size, but im sure theres more to it than that. ive read quite a few posts of people doing the head swaps, and most are happy with it, but you dont see the true potential until you do the efi. even just to bolt in a stock 4.0 would feel better than a head swap, IMO.

[Zorm]

ok, thanks for the info so far.
I have already done the 4.0 head swap along with a HEI dizzy and the morotcraft 2100 2 bbl carb. Now I was going to toss in a 4.0 with the 2000 intake and up grade to MPFI but after taking the head off the 4.0, I found that the engine needed more work than my already running 258 with the 4.0 head. So, I thought why not just swap over the serp drive stuff I got from a 2001 and run the intake while up grading to the MPFI. So my thought is, would this be kinda a "stroker" then as far as the low end torque and highway driving?
So, then I saw on a few posts that folks were having issues swapping a serp belt onto a 258 that was v belts due to removing the harmonic balancer and causing vibration issues. Anyone hear of this?

[Missourian]

So, then I saw on a few posts that folks were having issues swapping a serp belt onto a 258 that was v belts due to removing the harmonic balancer and causing vibration issues. Anyone hear of this?

Harmonic balancers do go bad. I would consider this as a possible source for the vibration.

[Zorm]

they go bad? I thought they were just a chunk of metal

[amcinstaller]

nope. two chunks of metal with some rubber in between them. the problem could have come from the balancers being pulled incorrectly. you need to use a special kind of puller, like a steering wheel puller to pull from the inside, not a standard pulley remover, or jaw type puller.

[tequila mike]

Correct me if i am wrong but for an engine to vibrate from an internal source without a catastrophic failure is near impossible.
Maybe a bad spark plug, plug wire, distributor cap. chunk missing from belt, missing fan blade.+++

[Missourian]

It depends upon the severity of the imbalance. Most OEM engines are not perfectly balanced but their close.

Some vibration is reflective of RPM, cam profile, and the performance of the aspiration system (FI, Carb). You thoughts on spark plug and timing are part of the big picture too.