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Old 09-21-2003, 09:15 AM
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350 Chev Compression ?

Recently purchased a car with a chev 350 and am trying to determine compression ration in order to choose a cam. It's a '71/'72 motor with fuelie heads/64cc chambers and flat-top pistons. Motor has about 10K since rebuild and previous owner doesn't know much more about it than what I told you. Current cam is stock.

Anyone know how I can determine compression ratio without pulling the heads?

Scott

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Old 09-21-2003, 09:23 AM
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Use the head casting numbers and determine the chamber size (64-...?) cc... And then you can determine a close ratio... If the pistons are true flat tops w/4 valve reliefs it makes it easier to figure...
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Old 09-21-2003, 10:26 AM
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I have identified the heads as having 64 cc chambers but can't tell if the pistons are true flat-tops without pulling a head.

Scott
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Old 09-21-2003, 10:40 AM
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What is the number on the block? Oh wait are they stock pistons? oppsy...if they are just us the block numbers and i think you can find the CR on the net.
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Old 09-21-2003, 12:31 PM
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compression testers are fairly cheap to buy id try that or borrow one like i do
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Old 09-21-2003, 12:51 PM
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What kind of numbers should I see with a compression tester. Is there a range that corresponds with 8.75:1 to 9.0:1, 9.0:1 to 9.25:1?

Scott
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Old 09-21-2003, 12:55 PM
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screw it in the spark plug socket start engine and run it...needle will go to what your compression is
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Old 09-21-2003, 01:20 PM
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It's probably around 9.5:1 - hard to say without more specs. No, a compression test can't really tell you.
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Old 09-21-2003, 01:25 PM
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I know how to use a compression tester, what I don't know is once I take the reading how do I relate that number to a compression ratio.

Scott

Okay, thanks for everyone's input. I think I better pull one of the heads to see what kind of piston I have and measure the deck heigth. Don't want to end up with a cam that requires a certain compression that I don't have.

Scott
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