Relieving 8BA Block

[JWL]

The false impression that relieving is good for competition engines because they operate at higher RPM will probably never die. Why? Because visual observations of Flathead flow paths seem to indicate a relief would be an improvement. Only after following the science with back-to-back flow bench and dyno tests can the facts be revealed.

The concept of using "seat-of-the-pants" as a point of reference or to collet data does not bode well for uncovering the facts. The fastest and quickest racing runs I have ever made actually felt the SLOWEST. I think this is because things happen very smoothly during the better runs. Those "hairy" runs with jolting wheel stands and power-drift crabbing at the top end are very impressive, but slow. Often there are those who make reference to speed records as proof of the value of relieving. But, since there are equally, or even more, magnificent records established with non-relieved Flatheads and since there is no way to determine how fast the sited record setter could have gone with no block relief, this is hardly a method which will determine validity.

I have no data on systems operating with air pressure beyond atmospheric.

[Ronnieroadster]

Originally Posted by JWL

The false impression that relieving is good for competition engines because they operate at higher RPM will probably never die. Why? Because visual observations of Flathead flow paths seem to indicate a relief would be an improvement. Only after following the science with back-to-back flow bench and dyno tests can the facts be revealed.

The concept of using "seat-of-the-pants" as a point of reference or to collet data does not bode well for uncovering the facts. The fastest and quickest racing runs I have ever made actually felt the SLOWEST. I think this is because things happen very smoothly during the better runs. Those "hairy" runs with jolting wheel stands and power-drift crabbing at the top end are very impressive, but slow. Often there are those who make reference to speed records as proof of the value of relieving. But, since there are equally, or even more, magnificent records established with non-relieved Flatheads and since there is no way to determine how fast the sited record setter could have gone with no block relief, this is hardly a method which will determine validity.

I have no data on systems operating with air pressure beyond atmospheric.

The Harley KR flathead using a releived block using atmospheirc air proved with data it is the best way to go on a flathead.

[JWL]

A relief on the Harley KR might have provided a flow or combustion improvement on the Harley KR. My testing has been confined to the Ford Flathead V8 where relieving is a waste of time, compression, and adds to the undesirable residuals in the unswept areas.