Jeep Strokers

A few months back, I picked up a 4.6L stroker off Craigslist. I'll be swapping it into my '74 International 100 pickup to replace a tired 258. I got a great deal because the previous owner couldn't get it to run right. He had a pretty extensive build/troubleshooting thread on here and it was interesting to read through the issues that led him sell it. No disrespect to him, as I got a bunch of good info from it.

So, I pulled the head today and found the pistons are in the hole a good 0.2". Not .02, 0.2". He also dished some KB Silvolites to about 20cc's, so I'm estimating the static compression ratio is just over 7:1. Combined with a Comp Cam 232, I can see why he had some serious idle and power issues. I'll have to verify, but I believe he used the 4.2 rods. This leaves me two options 1) deck the block down to kill a lot of that quench or 2) use the long rods and use a thick gasket to deal with pistons .05 out of the hole.

Any thoughts? Can the block be decked that much safely? He said he already decked the block .035".

Verify what crankshaft is in it, sounds like a 3.5" stroke not a 3.895

What's the bore on the block?, it sounds like a stock 258 to me?

It is a 12-weight 4.2 crank. I just double-checked the stroke. He used the 4.2 rods, as well. It is a 4.0 block out of a '94 ZJ with stock 3.875" bore. 7120 head.

I'm thinking the KB pistons have the wrong wrist pin height. Decking the block the amount needed doesn't seem feasible. I'm thinking either longer rods or new pistons with a taller pin height.

Here's a pic at TDC.

Just curious where you were located? I saw a 4.7 listed on my local craigslist & it disappeared about a week ago. Curious if this is it.

I'm in Orange County, engine purchased in Escondido area. I bought it months ago, though.

Shadowdrop wrote:So, I pulled the head today and found the pistons are in the hole a good 0.2". Not .02, 0.2". He also dished some KB Silvolites to about 20cc's, so I'm estimating the static compression ratio is just over 7:1.

Any thoughts? Can the block be decked that much safely? He said he already decked the block .035".

Looks like the PO used the 258 crank, 258 rods, and KB forged IC944 pistons. Those pistons are supposed to go with the 4.0L rods so your best solution is to get a set of those and sell the 258 rods.
You'll end up with the pistons ~0.008" above the block at TDC but that's fine. With a 0.043" head gasket the quench will be a nice, tight 0.035".

I think you hit the nail on the head. I believe these are IC945's that he dished further, bringing them close to the IC944's in total dish. Looking at the underside of the pistons, these are definitely forged and not cast like the 2229c's. I guess I'm shopping for some reconditioned 4.0 rods! The 4.0's require different rod bearings, right?

Ugh, I just re-checked the stroke and it's 3.5"! I have a feeling the PO thought he found a 258 crank and really had an old 232 crank. So, he essentially built a 4.0 with short rods. I may need to pull my 258 and use that crank.

Shadowdrop wrote:Ugh, I just re-checked the stroke and it's 3.5"! I have a feeling the PO thought he found a 258 crank and really had an old 232 crank. So, he essentially built a 4.0 with short rods. I may need to pull my 258 and use that crank.

Ooof. Check the casting number on the crank. What a pity that someone put some time and $$ into a build and did not take the time to confirm the combination of parts were correct. I hope you got a good deal on it. I would go through the whole thing and verify what was done. Keep us posted.

3214722 - AMC 1972-74 232 3.8 3.75 L-6 W/Rocker Shaft, Spec. Flat Back or Flanged Style Crank. I got a good deal, thankfully and I have a 12-weight 258 in my original engine. So, not a total loss.

Shadowdrop wrote:Ugh, I just re-checked the stroke and it's 3.5"! I have a feeling the PO thought he found a 258 crank and really had an old 232 crank. So, he essentially built a 4.0 with short rods. I may need to pull my 258 and use that crank.

If the PO really used the 232 crank then the pistons must be stock replacement cast pistons (probably Silvolite 2229) on 258 rods.
You could either:

1. Keep the 232 crank, cast pistons, and add 4.0L rods for a mini-stroker.
2. Use your spare 258 crank with the existing 258 rods/cast pistons to build a full 4.6 stroker.

Whichever rods you use the rod bearings (and rod bolts) are the same anyway.

Mini stroker ftw! I regret not aiming for more compression on my build. I ended up right at 9.0:1 & 7.8:1. Quench of .038.

I could of run 9.5-9.8 happily on pump gas without issue I think.

So, a year later and I finally got back to this project. Unfortunately, with bad news. My buddy had a 4.2 crank but it was thrashed. I had my machine shop go through everything else and here's what they found:
Rods were ground wrong. Ground across and not along the length of the rod, and ground on the pin boss areas. Not smart. Trash.
The "brand-new" cam is trash. The distributor gears are mangled.
Piston rings installed in the wrong order.
Pistons were balanced wrong. More grinding on the pin boss areas. Maybe trash, maybe not but I won't be able to use them because....
Block was decked but never bored/honed. The worst cylinder-to-piston clearance was .09, shouldn't be bigger than .02. Also, several cylinders out of round. They'll need at least a .020 over bore.

So, I'm having the block cleaned, mag'd, and checked. If all is good, I'll bore/hone the cylinders and start over. My shop thinks they have a crank and rods for me. I'll have them dish out some new 2229c's, new rings, install ARP bolts on the rods, a good crank, new bearings, new cam. Then I'll be back to where I started and I can think about swapping this into my truck.

Mickey Mouse wrenching!