Jeep Strokers

Hello, long time lurker, fist time post ...
So I chose the KB424C-030 pistons for my build ...
Using 4.0L rods obviously.
From my understanding this combination will have the piston .027" down in the bore.
Since this is all fairly new to me (stroker, not mechanics), should I have the block decked .020" or combine a .010" block and head clean up and call it done.
Now, this engine will be for my 88 Comanche, daily driver/trail rig and tows a 3500lb travel trailer 1480 km (return) once a year for work. It sits on 35's and has 4.56 gearing with an AX15 5spd. When towing I drop to a set of 255/75R17 to reduce the marshmallow effect.
Generally it runs from idle to 3000rpm (shift point), cruises at 18-2500rpm (speed dependant) and once in a while sees 4000rpm (rarely). I currently run a shadbolt rockcrawler grind on a stock core, so she starts to wheeze over 3500rpm, and pulls hard off idle.

Which leads to the second part ...

I have two cranks available ... One 12wt from and early 80's block, and the other is an 88YJ crank which from my understanding will be a lighter 4wt crank. Which would be better suited? I like the idea of the heavier crank for crawling, but I also daily this pig, and add in the need to tow periodically, I'm wondering if the later YJ crank might be a better choice.

I know about Russ's pistons, I just honestly can't afford them sadly. This is a "simple" low budget replacement build. My current 97 block has reached the polished bore stage.

My advice is:

1. Deck the block 0.020" and merely flat mill the head.
2. Use the heavier 12cwt crank.

Cheromaniac wrote: ↑January 24th, 2022, 12:03 am My advice is:

1. Deck the block 0.020" and merely flat mill the head.
2. Use the heavier 12cwt crank.

X2,

I would only add to this would be sure you punch in all the numbers in the compression calculator to make sure and verify you come up with the correct static compression ratio when done.

If you are going to deck the block why would you not zero deck it?

On a 4.6 stroker with IC944 pistons, the static CR will typically come in at ~9.6:1 if you shave 0.020" from the block deck. Going for zero deck clearance would raise it to ~9.75.

Using the KB242C numbers (0.030" overbore and 27.5cc dish), it looks to produce a stockish 8.85 static and 7.37 dynamic ratio's at 0.007" deck height. I used a lunati 63503 as it most closely resembled the cam grind I have currently.

This is how it looks on the outputs

Is 7.37 dynamic CR too low? Can you post the full calculator?

The stock Renix numbers produce 8.7 static and 6.36 dynamic CR's so this looks about right to my eye.

Had to screenshot it in three parts. My phone doesn't play well with the format of the calculator.

This doesn’t address the OP’s question but I just want to throw out some general information regarding the choice of a piston

Significant advantages to tightening up the quench.
If you’re able to put the piston at .035 to .045 from the cylinder head including head gasket at TDC, you’ll easily be able to 87 octane at a static compression ratio of 9.5:1

This only applies to a normally aspirated application and with a piston dish that is a reverse mirror image of the combustion chamber of the cylinder head. Meaning it’s not a full circular dish.

Cheromaniac wrote: ↑January 24th, 2022, 11:14 pm On a 4.6 stroker with IC944 pistons, the static CR will typically come in at ~9.6:1 if you shave 0.020" from the block deck. Going for zero deck clearance would raise it to ~9.75.

Wouldn't you want 9.75 cr with the cam specs listed? Dynamic cr comes in at 7.94 at .040" quench.

That would be fine.