Valve to head clearance

[cadillac512]

I just built an 8CM engine with original iron heads that looked to be untouched. With a depth mic measuring the areas over the valves, closest point on most chambers was .375" from machined head surface to roof of chamber.

I also checked cc's on the chambers, and don't have the notes with me right now but the numbers agreed with what I've read in this forum and other sites,also leading me to think no prior milling was done.
So...take this info for whatever you think it's worth, and measure your own to make sure!


Terry

[rotorwrench]

Ford made the chambers large in the Mercury 8CM heads so that is could pull well. The Mercury cars are relatively heavy. The 8RT truck heads have even more room in the chamber. They should be OK with a cam but you should always check with clay or aluminum foil to see where the valves end up. With a blower, you can afford more chamber room and still have good flow. Folks that don't use a blower commonly use the 1952/53 EAB Ford car prefix heads and router the edge of the pockets if needed but that's usually after they are milled for piston clearance. That might be too much compression for a blower application but I don't know if there is such a thing with the flatheads.

[Desoto291Hemi]

My 8CM heads mic about .376 -.382 in most of the chambers,,,,so that is pretty much dead on from the factory I would think.

I plan on doing my heads last after I have done all the valve work.

Tommy

[Karl Wolf]

I put the whole engine together, and with no head gasket, and the heads loose, turn the engine over.
Look for the heads to be lifted off the block by the valves.

If there is no valve to head contact, there will be at least the thickness of the head gasket to provide valve to head clearance.

Karl

[elwood]

Thanks again all ..