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Old 12-01-2019, 03:27 PM   #7
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Join Date: Dec 2010
Location: East Coast in CT
Posts: 651
Default Re: Flathead domed pistons and 21A rods

Originally Posted by JWL View Post
Adding compression has nothing to do with exposing the weakness of the 21A connecting rod. The 21A rod will fail at high RPM, on the exhaust stroke, at the pin end, just below the pin bushing. New 21A rods will usually withstand 3 drag strip runs at 6800 RPM in the lights when used with maximum lightened pistons and pins. However, if anything, ANYTHING, happens in the driveline and the engine buzzes to 7000 RPM, for only one second, they will do serious damage to the engine.

As OlRon says, the best first step for improving your Flathead is to bump up the compression ratio. Adding compression or displacement are the only methods for improving power and efficiency at nearly all RPM levels.
We learn something new every day sure glad Im reading all this so i can learn how to do this high performance stuff with the Flathead!
I use the F word a lot no not that word these words Flathead , Focus and Finish.
"Life Member of the Bonneville 200 MPH Club using a Ford Flathead block"
Owner , Builder and Driver of the First Ford Flathead bodied roadster to run 200 MPH Record run July 13, 2018 LTA timing association 200.921 from a standing start in one and a half miles burning gasoline.
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