Compression Ratio

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Jun 1, 2007 | 02:08 PM

cts1954

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From: Peterborough, Ontario

Compression Ratio

I was been working on my heads with success so far, I have measured and calculated the compression ratio as it is just above 9:1. What is the ideal compression ratio for a 255 flathead slightly modified. Now is the time to make adjustments if neccessary. Thanks for you input.

wgc

Last edited by cts1954; Jun 1, 2007 at 02:26 PM.

Jun 1, 2007 | 02:53 PM

4tl8ford

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From: Erie, pa

I think a nice streetable Flatmotor is in the 8.5 - 10 range with all cyl balenced.

Jun 1, 2007 | 06:52 PM

ALBUQ F-1

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From: NM

I don't think I'd go any higher than 9:1. Is that including the head gasket volume?

Jun 1, 2007 | 07:44 PM

cts1954

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From: Peterborough, Ontario

Compression Ratio

Yes, I used .040" as a compressed gasket thickness. Would it run better at 8 or 8.5:1.

Thanks

wgc

Jun 1, 2007 | 10:24 PM

4tl8ford

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From: Erie, pa

What cam are you running?

Jun 2, 2007 | 07:53 AM

cts1954

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From: Peterborough, Ontario

It is a 3/4 grind, I believe it is a copy of an Insky Jr 3/4 with around a .5" lift. I made a mistake by putting this cam in and I should have went with a milder one.

wgc

Jun 2, 2007 | 07:55 AM

F6Guy

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depending on your duration but the larger cam might benefit from the higher compession.

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Jun 2, 2007 | 10:31 AM

4tl8ford

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From: Erie, pa

The Isky 400 Jr has a Lift of ,400 and a duration of around 258.
I have a friend running one in a 296 with 10.5 cr in a Roadster, it can get a little touchy in heavy traffic.
Depending on which block I finally use that could be my setup, but I will have an additional 800/900 lbs over the roadster making it a little more friendly.