Jeep Strokers

What is a safe Compression Ratio for a stroker to run 5 PSI of boost?

I currently have the following:

4.5L Low-buck simple stroker

~ Jeep 4.2L 3.895" stroke crank
~ Jeep 4.2L 5.875" rods
~ Jeep 4.0L 3.875" standard bore pistons
9.7:1 CR
~ CompCams #68-231-4 206/214 degree camshaft
~ Stock 0.051" head gasket
~ Ford 24lb/hr injectors with stock 49psi FPR for '96 and later engines
~ 260hp @ 4850rpm, 321lbft @ 3500rpm ?

4.6L Low-buck stroker

Option 1: Same as above except:
~ Speed Pro H825CP +0.060" bore pistons
~ 9.5:1 CR
~ Unknown quench height
~ 260hp @ 4800rpm, 324lbft @ 3500rpm ?

on the recipe page there's a good list for mild boost.

NEW: Modified "poor man's" stroker

Jeep 4.0L 6.125" rods, Keith Black UEM-IC944-020 forged pistons, and 0.070" quench height. This is a great stroker build for a mild supercharger/turbo application with up to 6psi of boost. The 4.0L connecting rod/IC944 piston combination offers 155g less reciprocating mass than the 4.2L rod/677P piston combination (1275g v 1430g), thereby giving this engine a potentially higher rpm capability than the traditional "poor man's" stroker.

5 pounds is not much but 9.5 is pretty close to the upper limit. I would not go any higher.

Coffee Commando wrote:What is a safe Compression Ratio for a stroker to run 5 PSI of boost?

A 9.5:1 CR should keep you well within the margin of safety but PLEASE DON'T RUN IT ON LOW OCTANE GAS.

My CR is about 8.8/1 with bulltear custom pistons and maximum boost about 5.5 psi. I'm running with I.O. 95 RON, without any knocking and without any electronic adjustament (so far).
Previously I broke my Titan engine with CR 9.6/1 (CR was about 10/1, measured by myself).

You had a failed Titan Engine too? I live in Ocala.

I had a cam failure with them twice, then I rebuilt it myself last year.

After I rebuilt it I wondered what I actually paid them for the first time because I provided ALL of the parts to them and then spent 2300 on the engine.

Then they rebuilt it for me after it failed for 730, no parts provided by me. Crooks, the whole lot of them. Especially stone-face.

My engine broke because I was running with the Supercharger M90 (I melt a piston), and the C.R. was too high and I didn't any electronic adjustment for the air-fuel ratio or spark advance.
Now I have two wideband air-fuel ratio sensors (cylinders 1-2-3, 4-5-6) and a knock alert.
I have seen two Titan engines with serious problems.

montelibre wrote: I have seen two Titan engines with serious problems.

Yes, me too. Unfortunately they were my own. I've heard of others having them fail as well from various forums for Cherokees.

montelibre wrote:My engine broke because ...the C.R. was too high... and I didn't any electronic adjustment for the air-fuel ratio or spark advance.

WOW, that was brave. I just finished the install on a Sprintex and will use the AEM FIC and controll the timing and the '7th 50lb injector'.

Several months ago I have bought a Split Second FCT-019B, but I do not installed it yet. I need tuning the electronic because the A/R is lean a few seconds sometimes at low load and low rpm.
When I install it I will be able to run with a smaller pully (I think about 7 psi) and safer.

I've got this figured out:

6PSI of Boost
180-190 engine temperature
8.7311 SCR
7.38 DCR (CompCams 68-231-4)
91 Octane

Would the stock cam for a 4.0 (non-Renix) raise my DCR?