Jeep Strokers

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I'm working on putting together a mild stroker for it. I'm trying to keep the CR as close to stock as possible, certainly not much more than 9:1. Here is my thoughts/progress so far:

-Purchased 4.2 Crank & Rods (had to settle for 4CW crank, couldn't find 12CW)
-0.010" decking of block
-0.010" head planing
-Stock thickness head gasket

This should result in a CR of about 8.9:1 and quench of around 0.018 below stock. I'm not real familiar with the quench value, what is desireable and if 0.018" below stock is good, bad or otherwise. I could also use some recommendations for cams.

Well, I'm pretty sure I didn't calculate something quite right. The combo I listed above will result in more like 9.5:1 from what I've figured. I'm a little unsure about aftermarket piston dish volumes for calculating so I presume there is some variation there. More than likely going to be using the standard Speed-Pro pistons

Why don't you go with a Mopar performance gasket? It'll give you a lower quench value which will help reduce chance of ping.

Off subject:
I'm from Ann Arbor myself, graduated form University of Michigan on December 06, Mechanical Engineering. I did ROTC so now I'm deployed to Iraq.

I've decided to go an alternate route altogether. The combo I was looking at just couldn't get good quench numbers. Here is what I've settled on:

-258 4CW crank
-stock 4.0 connecting rods
-KB944 pistons (21.7 cc dish & 1.353 comp. height), no more than 0.030" over depending on what the shop says upon gaging the block
-0.020" decking of block
-Comp Cams X4250H-13 cam


This should result in good CR and quench numbers

CR: 9.35:1
Quench: 0.0605" (0.012" above stock)

This is going to cost me a bit more since the forged pistons are about $75 each but in the end I think it will be more reliable and run better with less worry of knock.

So I'm trying to find a little more info on using the 4.0 connecting rods. They are longer so custom pistons are needed. I was already planning on boring 0.060" so I'd need new pistons anyway. Any benefit to either the 4.0 or 4.2 connecting rods when going 0.060" over?

PolloLoco wrote:So I'm trying to find a little more info on using the 4.0 connecting rods. They are longer so custom pistons are needed. I was already planning on boring 0.060" so I'd need new pistons anyway. Any benefit to either the 4.0 or 4.2 connecting rods when going 0.060" over?

Keith Black makes a forged stroker piston using the 4.0 rod(kb944 and kb945), so you don't have to have a piston made. The 4.0 is a longer rod, so it would be better to use. A longer rod puts less piston side load on the cylinder and longer dwell at TDC.