New 4.2L mini-stroker recipes

[jpradcliffe]

Hey, thanks alot. I really appreciate it! I've got a 96 4.0 head that I ported and polished, port matched to 99 intake and valve job. Purchased a 232 from a 72 gremlin. going to harvest the crank and run stock bore silvolites. No dish and the comp #68 cam you recommended...looking forward to the 10:1 compression!

Question. What pistons would i need to run in the 232 with the 4.0 crank, so as nit to waste a good carbed motir?

[Cheromaniac]

Here's your answer:

4.2L Wilder mini-stroker

AMC 232 3.500" stroke crank
Jeep 4.0L 6.125" rods
Silvolite UEM-2229 +0.060" bore pistons
9.6:1 CR
CompCams 68-235-4 210/218 degree camshaft
Russ Pottenger ported HO 2.00"/1.55" 62cc cylinder head
Mopar/Victor 0.043" head gasket
0.040" quench height
Ford 24lb/hr injectors for '96-'04 engines
268hp @ 5300rpm, 303lbft @ 3900rpm

[jpradcliffe]

Looks schweet!

What I am asking tho is, can i use my 4.0 crank in the 232 block? What pistons would I need to do that? Thanks in advance.

[Cheromaniac]

You could but why bother?

[Cheromaniac]

What I am asking tho is, can i use my 4.0 crank in the 232 block? What pistons would I need to do that?

The 232 block has a deck height of ~9.531" so if you use the 4.0L crank (~3.411" stroke) and 232 rods (~6.125" length, same as 4.0L rods) to recycle those parts, you'll need pistons with a compression height of ~1.700" to achieve zero deck clearance (quench height 0.045" with 0.045" thick Felpro 8169PT head gasket). If you overbore the cylinders by 0.060", the result will be a 3.810" bore and a displacement of 233.3ci (3824cc or 3.8L). You could go for an 8.8:1 compression ratio (Felpro head gasket, 9cc dish pistons) and use a mild performance cam e.g. Crane 750501 to give the engine great low/midrange torque. Pistons would have to be custom made to the aforementioned specs (3.810" bore, 9cc dish, 1.700" compression height) as you won't find any off the shelf.
Your cylinder head options are also limited so your best bet would be to have the stock 232 head refreshed and ported to improve airflow. I'm not sure if the higher-flowing 4.0L head would be compatible with the 232 block.
You obviously want to keep the engine carbed so you could reuse your existing intake manifold and add a 390cfm Holley carb with a 4-barrel adapter.
Giving your old 232 a new lease of life with a nice boost in performance could be an interesting, low-cost project. Now there's some food for thought!

[jpradcliffe]

Hmmmm. So is there a combo, maybe different rods or crank, that wouldnt require custom pistons?

[Cheromaniac]

Unfortunately not. You could potentially use a set of aftermarket 258 pistons but there are two problems with those:

1. They're not quite tall enough so you'd need to shave quite a bit off the block deck (as much as 0.070") to achieve a decent quench.
2. The dish volume is too high and the result would be a compression ratio (~8.0:1) that's too low to provide decent performance.

[jpradcliffe]

Ok man thanks! I'll let you know how my wilder mini stroker turns out.

[jpradcliffe]

Wait a sec. Can i not use a 258 crank? Yes. Right? But what pistons? Is there an engine calculator i can use, instead of pestering you?

Heres a few of my jeeps as well

[Cheromaniac]

Wait a sec. Can i not use a 258 crank? Yes. Right? But what pistons?

Of course you can use the 258 crank in your 232 block and end up with, you've guessed it, 258ci of displacement with standard bore pistons (266ci with 0.060" cylinder overbore). Then again, why not use the 258 crank in the 4.0L block and build a 4.7L full-blown stroker instead of a 4.2L mini-stroker?

[jpradcliffe]

Yes, of course. I like the idea of the mini stroker as as opposed to the 4.7 for the fact that its cheap and cheerful.

[jpradcliffe]

Another question: There seems to be alot of confusion/ misinformation about pre 1988 jeep 4.0 valves being a different valve size diameter than post 1988 4.0 valves. As far as I can tell there is not a difference, maybe I am wrong.

So my question to the experts is: can I use the Comp Cams K kit #68 235-4 or not?

Here is the link: https://m.summitracing.com/parts/cca-k68-235-4

Thank you in advance and I look forward to your input.

[Cheromaniac]

The valve sizes on the Renix 4.0 and the HO 4.0 were the same (1.91" intake, 1.50" exhaust).
You can use the cam kit you mentioned but I wouldn't use the valve springs (too stiff) that are included in that kit.

[Russ Pottenger]

The valve sizes on the Renix 4.0 and the HO 4.0 were the same (1.91" intake, 1.50" exhaust).
You can use the cam kit you mentioned but I wouldn't use the valve springs (too stiff) that are included in that kit.

To expand and clarify Dino's comments.

It's a little misleading how Comp set up their kit and components section for AMC/Jeep/Chrysler.

Camshafts, lifters, and timing sets can't be shared throughout the six-cylinder family of engines.
The earlier 199-258 engines utilized a 3/8 valve stem and had a different installed height the the 242/4.0 engines.
Therefore the valve springs retainers, valve locks, and valve seals supplied in that kit will not work on a 4.0 head.

If you're willing to upgrade the stock valve spring, I stock the 68-235-4 cam on 114° lobe separation angle rather than the 111°. That would produce better manifold vacume.

[Cheromaniac]

I stock the 68-235-4 cam on 114° lobe separation angle rather than the 111*. That would produce better manifold vacuum.

You're the man yet again.