Mark here’s what you’re dealing with.
Note that in my photos my flow bench adapter plate I made is for a .030” 350, or a 3.91” bore.
The shallow side of a 6X head be it a dash 4 or dash 8 is .240” deep.
The head in my photos is a dash 4 just to be clear.
So this is what I found.
this means that with
No head gasket and
Zero deck
You can only run .470” lift when using the 2.11” valve before the valve hitting the cylinder wall.
The shallow side of a high comp 670 head head for example is about .200” deep.
My second photo is a 1.96” valve in the 6X head and there’s no issue with it hitting the cylinder wall.
It would be nice to have a chamfer at the top of the bore with a 1.96” valve , but in my opinion a 2.11” valve demands it .
Keep in mind that Pontiac used chamfers even in the bore of many 455 motors.
__________________
Wernher Von Braun warned before his retirement from NASA back in 1972, that the next world war would be against the ETs!
And he was not talking about 1/8 or 1/4 mile ETs!
1) 1940s 100% silver 4 cup tea server set.
Two dry rotted 14 x 10 Micky Thompson slicks.
1) un-mailed in gift coupon from a 1972 box of corn flakes.
Two pairs of brown leather flip flops, never seen more then 2 mph.
Education is what your left with once you forget things!
Last edited by steve25; 11-20-2025 at 06:04 PM.
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