ZZ4 compression ratio mystery...
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From: Charlotte, NC
ZZ4 compression ratio mystery...
The ZZ4 is rated at 10:1 compression ratio, I can’t figure out how they got that. The pistons are 6cc valve relief’s, the head gasket is .051, and the heads are 58cc. According to this calculator: http://216.121.161.76/files/EngineCalculator.xls that should make the compression ratio of the ZZ4 9.73:1. Can anyone shed some light on this?
The reason I would like to know I bought a GM goodwrench caprice engine which comes with ZZ4 pistons and I am putting ZZ4 / corvette heads on and I am trying to figure out what my compression ratio will be.
[Modified by 89 Iroc Z, 2:06 AM 12/17/2003]
The reason I would like to know I bought a GM goodwrench caprice engine which comes with ZZ4 pistons and I am putting ZZ4 / corvette heads on and I am trying to figure out what my compression ratio will be.
[Modified by 89 Iroc Z, 2:06 AM 12/17/2003]
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Re: ZZ4 compression ratio mystery... (89 Iroc Z)
Wow,Thats a good question and I really dont know.Maybe GM rounded it off to 10:0:1? Didnt "Ford" do that with their 4.9 liter engines back in the 80's and called it a 5.0?
Anyways,is there any extra math that may require something like deck height,milling,machine work,different head gasket thickness,etc, etc?Maybe you need to find out if the ZZ4 short block is the same as this caprice engine block youre using.Maybe the blocks have different part numbers(If GM didnt round the compression numbers off) and that affects compression ratio.Something to check out.Im unsure if youll find the answer here.
:)
[Modified by Bill's86Coupe, 1:51 AM 12/17/2003]
Anyways,is there any extra math that may require something like deck height,milling,machine work,different head gasket thickness,etc, etc?Maybe you need to find out if the ZZ4 short block is the same as this caprice engine block youre using.Maybe the blocks have different part numbers(If GM didnt round the compression numbers off) and that affects compression ratio.Something to check out.Im unsure if youll find the answer here.
:)
[Modified by Bill's86Coupe, 1:51 AM 12/17/2003]
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Re: ZZ4 compression ratio mystery... (89 Iroc Z)
I went to your link and played, a little. Your question does not address deck clearence. With a .030 deck, I too get 9.73:1. Just for grins, I plugged in .020, and got 9.95:1. THAT you can round to 10.0:1. Measure the deck height on the new engine. If you don't like it have the block decked. Use a different gasket. Don't forget about production tolerances. I'd be surprised if those heads are really 58 cc. You might want to check them. No mystery, just not enough facts. Good luck, and...
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