Jeep Strokers

Hey all,

My first stroker build for my 2001 XJ is well underway at this point (after breaking a piston skirt at 240,000 miles)... Below is the recipe I've used thus far:

• Stock/original 4.0 block, bored .040 over.
• Stock/original non-TUPY 0331 head (hey, it made it 240k, and I'm a masochist - let's just call it an experiment).
• Silv-O-Lite UEM 2229 pistons (+.040) (11cc dish is what Silv-O-Lite told me).
• Comp Cams 68-115-4 camshaft and lifters.
• AMC 232 crank (apparently the one I received is .020" undersized, with matching bearings).
• Stock valvetrain and valve springs (fresh valve job though - new seats and seals, ground, etc).

Long story short: I took the pistons to a machinst and asked them to dish them to 22cc, and then install them on the rods. I come back to a set of assembled pistons and rods with NO dishing having been performed (apparently they couldn't figure out how to do it). Apparently due to an internal error they assembled them anyway, so I've been patient and decided to forgive them... I called every other damn machine shop in San Antonio, and nobody could dish them, nor did they know of anyone who could. Given they had been installed, I'd be out the cost of another new set anyway, so I decided to proceed with the build.

I took the block and head back to the machine shop for a test assembly to determine how much the block needed to be decked to hit a .030-.045 quench height with a Mopar Performance gasket (.043 compressed). Based on the mini-stroker recipe thread here, I anticipated up to .020 needing to be removed...

Turns out that with NO changes to the deck height, I'm already sitting .004-.005 out of the hole?! Between this and the fact that they needed to take .010 off the head while working it over, I'm starting to worry about my resulting static compression ratio.

This leaves me with a few questions:

1. How much did that .010 affect my combustion chamber volume? I know stock is ~58cc.
2. Given that the 68-115-4 cam only adds .002 of lift on exhaust (and brings the intake lift up to match), I should be fine sticking with my stock valve springs, right? The shop tested them and verified they're still within factory spec (but I don't have the exact numbers).
3. With .010 having come off the head, but the block being at stock/original deck height, I *should* be able to re-use my original pushrods (provided I can find a head gasket in the ~.053 territory), right?

Thanks for y'alls help in advance. Let's avoid any argument on the 0331 head, though - this was a deliberate decision because I'm a masochist and would love to be that one sh*thead with an anecdote saying the 0331 is perfectly fine. That, and I want to stick with the factory 2-piece exhaust manifolds (already replaced 2 different 1-piece manifolds on this effing engine over the years due to cracking, and outright refuse to spend $600+ on quality two-piece headers).

Pic for attention:

Not sure why I didn't realize this before but...

1. Ignore the decking question. I forgot this is one of the reasons I went the mini-stroker route. Seems like .005 out-of-the-hole is pretty common on these setups.
2. Rough math indicates I lost about 2cc's to planing of the head .010". This assumes a perfectly cylindrical relief in the head, though, so it may be less based on the actual shape.

The valve spring question with the 68-115-4 remains, though. Any and all input would be most appreciated!

One last update... The more I read about the relationship between static compression ratios and cam profiles, the more it seems like the 68-115-4 has insufficient intake duration for a ~10.2:1 compression ratio, and detonation/pinging is possible. Is this true?

Man, I sure do seem to love asking questions before really doing my research... And talking to myself, as a result.

Ended up getting a hold of Comp Cams support and explained my situation, and they confirmed that the 68-115-4 was *not* a good cam for the specs I provided (10.2:1 static compression ratio was too high for such short duration, and not enough lobe separation/vacuum for the 2001's EFI setup).

Since I'm shooting for less lift (stock-ish valvetrain - likely heavier springs once broken in), they recommended a custom grind of the 68-201-4. Same specs, but with 113° of separation (instead of 110°). Given that I'm doing a double-roller timing setup, I've had them do the grind on the old style blanks (confirmed my timing cover has the little nipple cast into it, and already have the bolt/spring/pin setup).

I'll post updates once I receive it in the next week or two, and will share my overall results.

Sounds like you're going for a mini-stroker recipe that somewhat resembles this:

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

The HP output will be lower in your case since you're using an unported 0331 head.

Cheromaniac wrote: ↑October 19th, 2018, 12:21 am Sounds like you're going for a mini-stroker recipe that somewhat resembles this:

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

The HP output will be lower in your case since you're using an unported 0331 head.

You got it, just with a hair higher compression ratio. I started with the milder stroker recipe you posted, only to discover nobody in town could dish the pistons... so I got stuck with the 11cc dishes on the same pistons. I also only went +.040" due to the price and availability of said pistons over +.060's.

Have you run into any issues with your recipes in EFI engines? The guy I spoke to at Comp was insistent that 110° LSA was insufficient for EFI (which is what the majority of the cams you recommend are spec'd at).

It won’t help you now, but to others I have a 2229 Silvolite CNC program for those looking for custom dish volumes.

I agree with the advice you received from Comp Cams on LSA on our computer controlled fuel injected Jeep engines.

I have a full shelf of Comp Cams with the lobe separation angle changed to 113°and 114°

Feel free to contact me,

Russ Pottenger
Bishop-Buehl Racing Engines
531 N. Lyall Avenue
West Covina, California 91790
Work (626) 967-1000
Cell (626) 673-2203
Email/PayPal: [email protected]

Thunderdonkey wrote: ↑October 19th, 2018, 6:24 am Have you run into any issues with your recipes in EFI engines? The guy I spoke to at Comp was insistent that 110° LSA was insufficient for EFI (which is what the majority of the cams you recommend are spec'd at).

The 110* LSA is quite narrow and can produce a low idle vacuum and poor idling if a longer duration cam is specified due to a longer valve overlap. Widening the LSA can mitigate that effect, hence Russ specifies custom CC grinds with a 113* LSA.

What color is the block painted btw? Looks like the same color as my Olds motor

SkylinesSuck wrote: ↑October 29th, 2018, 5:26 pm What color is the block painted btw? Looks like the same color as my Olds motor

AMC Blue - had to give a nod to its roots (first engine build, so I might as well have some fun, right?).

Everything is starting to finally come together... Installed a custom-ground CC cam (basically 68-201-4 but with 113° LSA) that was better suited for the ~10.3:1 CR I've ended up with, but still somewhat mild since I didn't do any head work beyond having it checked and planed.

That being said, I've run into a weird issue with regard to pushrod length... Using a CC 7704-1 checker, I understand that the easiest way to check for the correct length is to drop the checker into the pushrod bore, install the rocker arm, and expand it until it's somewhat snugly seated against the arm (each rotation being 0.050")... and then add 0.040-0.060" for correct preload. In doing so, I got 14 turns to get it to the "snug" length, meaning I'm looking at a length of ~9.540-9.560". Stock length is 9.640".

Given that the machine shop only removed 0.010" off the head, nothing from the block, and I'm running a Mopar Performance head gasket (already installed and torqued, 0.044" compressed thickness), how am I in this situation? I figured I'd be within spec to re-use the factory pushrods.

It would be better if you can find someone with a 12" dial caliper to measure the length of the pushrod checking tool. Otherwise it's an educated guess. Hate to see you buying more pushrods later. Ask me how I know....Haha.

GreenYJ wrote: ↑November 20th, 2018, 5:11 am It would be better if you can find someone with a 12" dial caliper to measure the length of the pushrod checking tool. Otherwise it's an educated guess. Hate to see you buying more pushrods later. Ask me how I know....Haha.

You really don’t need a caliper.

Comp Cams Pushrod Length checking tool #7704-1 measures 8.800 to 9.800 and is clearly marked, and every evolution is equal to .050
For about $20.00, it’s a good tool to have in your box.