mustangs killer

Does anyone know the cc volume of a .125 domed piston. The piston is for a 355. I need to know it to find my compression ratio. Thanks

The ODB

approx 12.87cc

mustangs killer

how did you come up with that? and if that is right the would the compression ratio of my engine be 11.3:1. The motor is 350 .030 over the deck height is .030 the gasket is .041 and the heads are 67cc. I hope that I caculated wrong or I'm going to have to change heads because that will never run on pump gas. Thanks

[This message has been edited by mustangs killer (edited March 10, 2001).]

The ODB

Well I did the math the best I could. If you don't count valve reliefs or ring land area or spark plug, then I come up with 11.54:1 compression.

Even with the tricks I know, that is still too high for iron heads. You would have to add 10cc to get down to 10.0:1

The best way I could think of is to just get some flattop pistons.

ODB

AlkyIROC

Ahh. Finally a cc for the dome. My calculations for your engine specs now put it at 11.544:1 compression. Way too high for any pump gas. If you put on some large 76cc smog heads such as 993's you can lower the compression ratio down to a reasonable 10.327. 92 pump gas may just get by with that.

mustangs killer

That can't be right. the compression should only be about 10.3 - 10.5:1. The valve reliefs in these pistons are deep. That should lower the compression,right? Anyways the company rated the piston at 10.23 with a 68cc head so mine should only be a little higher, or am I wrong. these are the specs. on the piston.
Sterling Pistons
Compression height: 1.560 in.
Compression ratio: 11.57:1 (58cc heads), 11.20:1 (60.5cc heads), 10.72:1 (64cc heads) , 10.23:1 (68cc heads), 9.78:1 (72cc heads), 9.38:1 (76cc heads)
Head type: .125 in. dome
Oversize: .030 in.
Ring size: (2) 5/64 in., (1) 3/16 in.
Weight: 596 grams

Vader

Yes. My 355 barely makes 423 BHP with 11:1 pistons on 93 octane gasohol. Any higher might be a problem.

(TRW MR4019-B, 12.9 cc of dome in 74cc heads. I calculate that the recess volumes of the 2.10/1.65 valves reduce the static ratio to 11.03:1, but that's close enough for argument.)

If you wnat a calculator, try this:

Engine Calculator.xls

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Later,
Vader
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"I'm'a do Things My Way - It's My way or the Highway."
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Guest

Using the information you gave above (are you sure about the pistons being .030 below the deck?) and the compression ratios and head cc's given by the manufacturer and assuming .022 below the deck from the compression height of the pistons, I came up with the pistons having a 2.3cc dome overall. That leaves your compression ratio at 10.16:1 given the .030 below the deck and .041 head gasket.
I have a catalog here, though its not Sterling, that lists a .100 dome piston and it has 1.2cc so the 2.3 is probably correct. To get up to a 12cc dome you are looking at around a .250+ dome... alot more than what you have.

AlkyIROC

OK Vader. I looked at your .xls sheet. Very nice however on the "typical values" sheet your combustion chamber sizes for big blocks is very wrong. You list them as low as 54 and as high as 76. One of the smallest combustion chambers offered was 98.4cc in cast iron closed chamber while most of the open chamber heads are 119 and the largest being 124.

mustangs killer

No i'm not sure about the deck height. My calipers are off a little. the read .022 but I bumped it up to .030 beacuse I know stock deck height is .035 so I just guessed somewhere in the middle. Thanks for all your help. I should have any probs. with that comression set at around 32-34 degrees total timing I shouldn't have any problems should I. Thanks again for everyones help.