Jeep Strokers

Hi All – This site has been an invaluable source of information for my stroker build, but I’m afraid I’m suffering from a bit of information overload. I built a “poor man” stroker with 4.2 crank & rods, Sealed Power H825CP pistons, bored +030, and stock deck height over the summer for my CJ-7 project, which sat until now, and I’m finally getting back to the final electrical and plumbing.

I understand from countless threads the advantages of the “modified poor man”, but why all the hate for the original poor man? I went this route because I already had all the components except pistons and rings. What am I not seeing here? Am I going to be OK to run this thing?

Based on 15.1cc pistons, 58cc chamber, stock .0215 deck clearance, .044 HG thickness, and stock 2002 GC camshaft, I’m calculating a SCR of 9.85:1, DCR 8.52:1 and .0655 quench. It was always my expectation to run 93 octane, but I’m reading threads saying I might be in trouble with these ratios. Will I be ok with 93 octane pump gas?

Also, I purchased a used head that had been leveled by a machine shop by the previous owner. I see changing the combustion chamber will have a potentially big impact on compression ratios, and I understand it’s a guessing game, but how much of a decrease would you typically expect from flattening the head?

Finally, can anyone confirm that the Victor 54249S MLS is .044 compressed? Information seems to be sparse.

Again, thank you all for all the insights.

The quench will actually be ~0.081" because the deck clearance with H825CP pistons will be ~0.038", and the HG thickness is 0.043". By my calculations, the SCR will be 9.63:1 assuming the chamber is 57cc.
While it's a less than ideal combination, you'll be fine running it on 93 and should be OK even on 91 octane gas. Just make the combustion chambers and piston dishes as smooth as possible to reduce the risk of pinging. Any work you can do to gain some chamber/piston dish volume and lower the SCR a couple of tenths will help, especially if you're going to run the stock cam.
You need not worry about long term reliability with the original poor man's stroker. Mine was still going like a raped ape when I sold it after 86k miles of use. The modified poor man's stroker is obviously a better build but for anything other than extreme use, the original poor man's can still get the job done.

Thank you for the reply and putting my mind at ease. Also, thanks for the clarification on the deck height. I built it based on an online kit that advertised a 9.6:1 CR, and I was wondering why my calculation was so much higher. While I know my way around a jeep, this has been my first engine build, and I've learned A LOT from this forum and the build process. It sounds like even with the components I used, I could have helped myself by polishing up the pistons, but with the engine assembled it's a little late for this build. They were far from shiny as they came from the supplier, but you think I'm still okay running 93 octane? I guess at this point, finish the plumbing and electric and see how she runs...

The build has been a very interesting and rewarding process. Once I have the CJ up and running, I'm looking forward to one day stroking my WJ or TJ, avoiding some of the pitfalls I encountered this time around. Thanks again.

R4TER wrote: ↑January 23rd, 2019, 10:31 amThey were far from shiny as they came from the supplier, but you think I'm still okay running 93 octane?

Yeah it'll be fine. Just run slightly colder plugs (Champion RC10LYC) than stock and a 180* t'stat if you live in a warm climate.