Jeep Strokers

I'm a long time lurker, first time poster. I am in the planning stages my first stroker. Sorry if the post is long, but I'll try to provide as much info as possible.

My Jeep is a '97 XJ, AW4, 4.56 gears & 33" tires. It is a daily driver / weekend wheeler.

Since it is nearing need for a rebuild anyway, I would like to upgrade. My goal is better acceleration and more useable power at highway speed. I have no intention to measure 0-60 times or take it to the track. I would like gobs of torque from off idle to 3500-4000, or so. Also, it needs to be reliable & long lasting. It will need to function reasonably well with OBD2 as I am not experienced in custom programming/tuning.

It would be great to be able to run on 87 octane, but if not, I could live with 89 or 92.

I think a cross between Cheromaniacs modified poor man's stroker & low-buck stroker may suite my needs. I would like to use the stock cam to keep costs down and make my first build as simple as possible. Here is what I came up with:

4.2L 3.895" crank
4.0L 6.125" rods
KB IC944-030 Pistons
Stock 4.0L HO Camshaft
Port HO Head
Mill Block for .008" Clearance
.051 Quench
SC 9.55:1
DC 7.88:1
.043" Head Gasket
24# Injectors

As you can see, it is pretty much the low-buck option, but with the stock cam (or a modified poor-man's with the block milled). It seems many people run the 231-4 cam. I am not opposed to a cam swap, but would it give any better low end grunt than the stocker or is it designed to breathe better at higher rpms? I do not want to sacrifice low-end power for horsepower made in an rpm range that I never use, anyway. Also, if anyone knows an ideal cam that suits my needs, I'm open to suggestions.

Would there be any measurable improvements to bore .060 over and use IC944-060 pistons to up the displacement to 4.7L? The SC comes out to 9.68:1 and the DC shows to be 7.98:1 if everything else in the recipe stays the same.

If I mill the block less to lower compression, at want point is it self defeating because of giving up quench?

Also, at the moment, I have pretty much standard upgrades installed:
AFE cold air
JBA Header
MagnaFlow converter
MagnaFlow Cat-Back
D.U.I. Coil, Cap & Plugwires
63MM Machined throttle body

Thanks for any advise.
Adam

adam518 wrote:I'm a long time lurker, first time poster. I am in the planning stages my first stroker. Sorry if the post is long, but I'll try to provide as much info as possible.

My Jeep is a '97 XJ, AW4, 4.56 gears & 33" tires. It is a daily driver / weekend wheeler.

Since it is nearing need for a rebuild anyway, I would like to upgrade. My goal is better acceleration and more useable power at highway speed. I have no intention to measure 0-60 times or take it to the track. I would like gobs of torque from off idle to 3500-4000, or so. Also, it needs to be reliable & long lasting. It will need to function reasonably well with OBD2 as I am not experienced in custom programming/tuning.

It would be great to be able to run on 87 octane, but if not, I could live with 89 or 92.

I think a cross between Cheromaniacs modified poor man's stroker & low-buck stroker may suite my needs. I would like to use the stock cam to keep costs down and make my first build as simple as possible. Here is what I came up with:

4.2L 3.895" crank
4.0L 6.125" rods
KB IC944-030 Pistons
Stock 4.0L HO Camshaft
Port HO Head
Mill Block for .008" Clearance
.051 Quench
SC 9.55:1
DC 7.88:1
.043" Head Gasket
24# Injectors

As you can see, it is pretty much the low-buck option, but with the stock cam (or a modified poor-man's with the block milled).

The only problem with milling the block to raise the SCR is that you could also raise the cylinder pressure above the detonation threshold. I suggest you polish the combustion chambers and increase their volume to 60cc (not difficult) if you're going to mill the block for a lower quench. With the stock cam you'll have a low rev torque monster.

So you suggest bumping up the combustion chamber to 60 cc's if I go for a .008 deck clearance to get quench to .051?

Would there be any advantage to increasing bore to +.60 and increasing combustion chamber size...versus a smaller combustion chamber at +.30 with the same compression ratio?

1. Yes.
2. Not really.

adam518 wrote: If I mill the block less to lower compression, at want point is it self defeating because of giving up quench?

Milling the block will lower your quench value but raise your compression. A lower quench can better handle a higher compression ratio than a higher quench. Getting quench and compression in the sweet spot will result in a better, more complete burn. My first stroker had much better (lower) quench than stock and a higher CR, but I was able to run low grade fuel without pinging whereas my stock motor wanted mid grade. From what I've seen through searching is that the optimal quench is around .055 - .045.

adam518 wrote: Would there be any advantage to increasing bore to +.60 and increasing combustion chamber size...versus a smaller combustion chamber at +.30 with the same compression ratio?

Since Dino says not really, I would go with only .030 over and give yourself room to go to .060 if you have to rebuild later. That is unless you just flat out want yours to be a 4.7.