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11-06-2013, 11:00 PM | #1 |
Senior Member
Join Date: Jan 2012
Location: s/w Louisiana
Posts: 119
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Offenhauser Heads
I just bought a set of offy heads stamped 375 anyone have any Idea what the compression ratio may be?
Tony |
11-07-2013, 01:14 AM | #2 |
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Join Date: Sep 2013
Posts: 14
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Re: Offenhauser Heads
The heads have 57 cc combustion chambers. Used on a stock 239 w/no relief the CR will be ~8.41:1, with a relief ~8.09:1. The CR will increase as the bore size increases. In a 255 (Merc) you're looking at ~8.90:1 with no relief, and ~8.56:1 with a relief. The reliefs quoted above would be .0100" and gaskets above would be at 0.057" thick. John
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11-07-2013, 08:42 AM | #3 |
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Location: Chester Vt
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Re: Offenhauser Heads
Best to measure them, the casting can be all over the place. The 375was for Valve lift, but this didn't clear the Max #1 in most cases with out some clearancing.
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11-07-2013, 09:27 PM | #4 |
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Re: Offenhauser Heads
Thanks John and Ol' Ron info will be a big help. Ron I am planning on running a Winfeild ¾ Cam do you think I will have valve clearance problems?
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11-07-2013, 09:35 PM | #5 |
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Re: Offenhauser Heads
That's impossable to answer. Depending on the net lift and if the heads have ever been milled. are they new or used.
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11-08-2013, 10:17 PM | #6 |
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Re: Offenhauser Heads
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11-08-2013, 11:25 PM | #7 |
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Re: Offenhauser Heads
.050" over pistons and the valves should clear, for a street engine the valve clearance isn't that important. the closer the higher the CR
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11-08-2013, 11:35 PM | #8 |
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Re: Offenhauser Heads
Thanks a bunch Ron I will mock it up and check in the morning.
Tony |
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