[steve25]

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.

[MarkS57]

Originally Posted by steve25

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.

Hi Steve, I'm looking at a 77 350 I want to wake up. I have a nice set of 62's that can bolt on tomorrow. So, beyond an 068 which I know will work, I'm considering a 2801 that gets close to .470.

[srmmmm]

Originally Posted by steve25

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.

My 1970 350 block is bored .060 over with .003 milled off the deck. The 6X-4 heads were milled .005 and Butler performance head gaskets used with a crush thickness of .045
Pistons are Ross flat top set even with deck height, Cam is Comp XE276HR with .502/.510 lift and 224/230 duration @.050 with 1.5 rockers.
442 Lb Ft @ 4300 and 453 HP @ 5600