Recut domes in EAB heads

[cadillac512]

A followup to the recut dome EAB head installation on my 260" Merc. I've run a few tanks of gas through it now, and where it previously delivered 16.5-17 mpg I am now seeing 18-18.7 mpg. The extra torque from the compression increase really has made a difference.



Terry

[Zeke3]

Terry, thanks for the update.

[38 coupe]

Originally Posted by cadillac512

I've run a few tanks of gas through it now, and where it previously delivered 16.5-17 mpg I am now seeing 18-18.7 mpg.
Terry

Thank you for the update. I find this very interesting, and per my memory is consistent with other back-to-back reports of modifying stock heads. Using the big flathead compression ratio file you increased compression from approximately 6.8 to 7.7 which is about 12%. You measured about 10% improvement in fuel economy. That improvement in fuel economy must come directly from improved power at the same part throttle.

The amount of improvement is much more than the normal theoretical improvement in power for a compression bump. I suspect this is because the theoretical compression benefits are not taking into account the improved combustion chamber dynamics that can be had in our ancient design side valve motors.