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914World.com _ 914World Garage _ Radius-ing heads

Posted by: krazykonrad Sep 18 2017, 08:41 AM

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Is there any performance advantage here or is it just to back off the compression ratio to avoid pinging?

Thanks,
Konrad

Posted by: Dave_Darling Sep 18 2017, 11:34 AM

In theory, sharp corners would provide hot-spots that would promote detonation.

In practice, I'm not sure it matters unless you have tuned your engine to the Nth degree.

--DD

Posted by: Mark Henry Sep 18 2017, 12:27 PM

Also called the Semi-Hemi, I used to do this back in the early nineties.
OK if you want to lower your CR, but I've found doing the math and shims under the barrels do a simpler and performance wise better job.

Posted by: HAM Inc Sep 18 2017, 07:31 PM

Sharp edges in iron heads are a problem as they can light off under pressure, like a glow plug.
Sharp aluminum edges turn dull when they get that hot, preventing the kind of pointed hot spots that light off.