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Old 04-28-2011, 09:41 PM
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will a stock bottom end sbc handle 11.5 to 1 compression

i have a stock bottom end 327 with 64cc heads its 10 to 1. but now im using 58cc heads n im thinking im around 11.5 to 1. my question is will the stock rods, crank etc handle a little amount of abuse.

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Old 04-28-2011, 09:55 PM
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It may all come down to the rpm but "a little amount abuse" usually turns into the big bang theory. if the short block is a well built 350 hp 327 then don't let 58cc heads stop you
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Old 04-28-2011, 10:16 PM
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The bottom end was pretty much the same from a 250HP 327 to a 375HP 327.
Shouldn't matter much what the compression ratio is.
As said, RPM is the main factor to consider.
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Old 04-29-2011, 03:02 AM
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Quote:
Originally Posted by crankshaft3rd
i have a stock bottom end 327 with 64cc heads its 10 to 1. but now im using 58cc heads n im thinking im around 11.5 to 1. my question is will the stock rods, crank etc handle a little amount of abuse.
Whatcha going to use for gas? E-85?
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Old 04-29-2011, 06:42 AM
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11.5:1 is in itself not a problem, the problem comes from the cam that matches 11.5:1 compression on gasoline- it'll put you in HIGH RPM's, like 7,000+. I would push thta RPM on a stock rotating assembly. If you plan to run E85 though and pick a mild cam that peak below 6,000 you'll be fine. The starter will feel the extra strain though.
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Old 04-29-2011, 12:45 PM
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Quote:
Originally Posted by crankshaft3rd
i have a stock bottom end 327 with 64cc heads its 10 to 1. but now im using 58cc heads n im thinking im around 11.5 to 1. my question is will the stock rods, crank etc handle a little amount of abuse.
About 11.37:1 w/the 58 cc heads.
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Old 04-29-2011, 02:10 PM
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If this a small journal 327 then I wouldn`t trust it unless it has aftermarket rods in it. To run that kind of compression will require 105 octane fuel, because if it goes into detonation you`ll be referring to the engine in the past tense. Detonation, small journal stock rods don`t go together well.
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Old 04-29-2011, 03:19 PM
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Quote:
Originally Posted by crankshaft3rd
i have a stock bottom end 327 with 64cc heads its 10 to 1. but now im using 58cc heads n im thinking im around 11.5 to 1. my question is will the stock rods, crank etc handle a little amount of abuse.
What is the fuel? and what are the heads made of?

The thing that really counts is the Dynamic Compression Ratio which is camshaft dependent. If that computes out around "8 to 9" to 1 then pump gas will cooperate having 8ish on the iron head side and 9 ish on the aluminum head side your OK with unleaded.

Chevy bottom ends are pretty robust they will be reliable up through about 450 hp and 6200 RPMs.

Bogie
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Old 04-29-2011, 03:43 PM
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I'm no cam guru but I'd think the lobe separation would have more to do with actual combustion pressures, or so I've been told.
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