I know there will be a small variance with almost every engine but I'm wondering what the factory stroke and combustion chamber CC would be for my '83 225 peanut head motor. I'm attempting to figure out my true CR since milling the block. There has been a bit of debate as to whose CR calculator is the best. Can anyone direct me to one that they feel confident with?

Thanks, Pat.

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My WAG... .185 down in the hole and 60 cc in the chamber.
Let me know if I win the Lotto...
DD

My combustion chamber came out around 58cc but I wasn't sure how accurate it was. After trimming .100" off the block my deck height is .047". I'm also looking for the actual stroke and for that matter, I guess I also need the thickness of a compressed stock head gasket (fiber, not steel).

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Sounds like you were pretty close to "spec" on the deck height.

For head gasket thickness, figure .040 for a Fel-Pro and .045 for all other composit type gaskets.

Stroke for a 225 is 4.125 and that is a good number to use.
DD

The calculator that I'm attempting to use is asking for the "piston dome volume (CCs) negative if dished pistons". Does this mean the combustion chamber volume plus the deck height CC? And if so is that just bore diameter times deck height?

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This calculator came-up with 9.6 to 1 C/R at a standard 3.400 bore size.
http://www.csgnetwork.com/compcalc.html

If the piston is a flat top, the piston dish / dome value is zero.
This calc. wants negitive deck as a positive value in that field.
DD

I was using the same calculator but I had measured my bore as 3.397 with a telescoping gage that isn't very accurate if you ask me. My figures came out to 9.509. I'll assume that my bore is a standard 3.400 and be happy with my 9.6 CR.

Thanks for all your help Doc, this has been a fun study, I look forward to doing our race 440 with the step head pistons.

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dd, using your calculator, my .030 225 -.084 deck 40cc head with a felpro shows 11.5-1. with a .020 mopar shim it shows 12-1. can the mopar shim gasket take 12-1? can a felpro take 11.5-1? which one would you use and why ? i have both. thanks ron

I would use the shim gasket on fresh / clean, machined surfaces.
A light coat of spray sealer on both sides of the gasket and ARP head studs torqued at 80 ftlbs. (or where ever the hone plate was torqued to)

Your cam specs will have a lot to do with the final cylinder pressure the head gasket really sees. You want to see around 185 -195 psi or a little more if you don't mind an "on the edge" race engine.
DD

i agree doug, on my 11.4/1 comp motor the fel-pro gasket had no trouble but on the blown motor , 5bls boost, it wouldn`t ho;d in high gear. the steel shim(used) with mopar spray sealer worked great.

d, i have a mopar 244/.436 cam for this engine. i was shooting for 200psi and want a max torque build, not a high rpm screamer. is there a erson or another cam that you would use or suggest? ron

is the erson cam group buy still going on? ron

Call Erson and find-out, I bet it is.
You are going to need more cam duration with that much static compression. Fuel quality will be an issue with your combo.
DD

Mine is 200psi with a 240@50 .518 cam advanced 2* and you know it when you get some 93 thats not all there. Total timing set at 24* After a heat soak thats still a little to much.

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67Cuda,FAST EZEFI,340cu,CR=10.25,RollerCam&Rocker (XR268HR,#20-810-9)(#1622-16)(EddyRPM#60779,#7576), (MSD6AL,#6425) A904, GearVendorsOD, 8 1/4,3.55:1, ClassicAir

Brennan,

Who made your cam, is it a custom grind?

Thanks,

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Aggressive Ted

http://cid-32f1e50ddb40a03c.photos.live ... %20Swinger


74 Swinger, 9.5 comp 254/.435 lift cam, 904, ram air, electric fans, 2.5" HP2 & FM70 ex, 1920 Holley#56jet, 2.76 8 3/4 Sure-Grip, 26" tires, 25+MPG