Could this be true???

Old 11-06-2009, 03:39 PM
  #1  
Scooterz
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Default Could this be true???

I was told by a guy who built a BBC that due to the amount of work done on a set of heads (extensive port & polish, valves etc...) + other things done to the heads I am not aware of... that the heads brought DOWN the actual compression of the pistons. Example: He said: "due to the amount of work done to the heads & pistons being 12.5's, the compression comes out @ 10.2". Is this BS??? How is it possible? Scooter
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Old 11-06-2009, 04:16 PM
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zipper06
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I doubt that, by doing the chambers and useing tuliped valves they might drop 1 point at the most. The porting it's self has no effect on the compression ratio, only the combustion chamber volume does.

JMO

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Old 11-06-2009, 05:35 PM
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Scooterz
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Okay that makes more sense to me. What is a tuliped valve exactly Zip?

(forgive my ignorance)
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Old 11-06-2009, 07:08 PM
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zipper06
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A tuliped valve is just what it sounds like, it's dished concave in the center to make it lighter, but they're not used too much any more with titanium readly avaible. They actually look like a tulip or morning glory flower and add a little to the combustion volume. They were real popular in the old days on sm/blk chevies, when we didn't have oll the good valve springs that we do today when the only roller cam manufacturer was Chet Herbert, and Isky was only making flat tappet cams. I'm talking mid 60's.

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Old 11-06-2009, 08:23 PM
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signsbyesa
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bought my first cam from chet herbert and he would answer the
phone himself, good guy rip
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