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Ol' Ron · 03-17-2018, 10:07 PM

The shape of the combustion chamber, not only controls flow, but also the CR. I've found a transfer area at a 12 degree angle provider good flow. But decreases CR. also the exit of the transfer area also has an affect on flow. For street I use an 8 degree angle for the transfer area and a 60 deg exit. I like to use Offy head for shaping the chamber because they are thicker than the Edelbrock heads.. Some consider flow behind the valve,but i couldn't prove that. I mill the area over the valve at a 5 degree angle. this removes less material to keep the CR as high as possible. With .045" piston to head clearance I can get 8.5 CR in a 276 ci engine. The next best thing would be to remove the spark plug to the center of the transfer area. This will shorten the flame front. Less detonation with a low grad fuel. Now that we're getting a new block, we might want to take another look at Flat 32's heads.

03-17-2018, 10:07 PM	#90
Ol' Ron Senior Member Join Date: May 2010 Location: Chester Vt Posts: 8,860	Re: 8BA tooling. The shape of the combustion chamber, not only controls flow, but also the CR. I've found a transfer area at a 12 degree angle provider good flow. But decreases CR. also the exit of the transfer area also has an affect on flow. For street I use an 8 degree angle for the transfer area and a 60 deg exit. I like to use Offy head for shaping the chamber because they are thicker than the Edelbrock heads.. Some consider flow behind the valve,but i couldn't prove that. I mill the area over the valve at a 5 degree angle. this removes less material to keep the CR as high as possible. With .045" piston to head clearance I can get 8.5 CR in a 276 ci engine. The next best thing would be to remove the spark plug to the center of the transfer area. This will shorten the flame front. Less detonation with a low grad fuel. Now that we're getting a new block, we might want to take another look at Flat 32's heads.