[steve25]

That’s good mark. I just hope you can move the valve enough to reach the limit you need to confirm.

Since you have a valve compressor I might take that spring off and then reassemble it with just the outer spring and then the lesser force needed to open the valve should allow you to open it as far as necessary without the keepers popping out on you.

[Squidward]

When I built my 72 350, I put the heads on with a used gasket, and checked max lift with low tension checking springs. Block had 2 chamfers each cylinder, at 40 over. I measured max lift of .509 with my big valve #12's before the valve contacted the bore. As a result, I made sure to keep my lift reasonable, so I went with the Lunati Voodoo 702 (219/227 @50, .468/.489 with 1.5 rockers). Checking with NO gasket would give even greater margin, and would build in a safety factor by the gasket thickness.

As mentioned, the safest plan is to measure, for sure. I checked a set of 061 heads I have, and the valve to deck clearance was definitely smaller. Rebuilds, milling, decking, etc can all stack up.

Thinking an 068 would be easily doable. And at .444/.466, the 2801 would likely be a fun cam in a 350 with the right converter and gears.

[Squidward]

Exhaust valve lift will be your constraint. Later 2.11/1.66 heads will likely give you more lift with the smaller exhaust valve.

Steve has probably forgot more than I will ever learn, so not looking to dispute. I just never saw an issue with the intake valve clearance, but the exhaust was the constraint in my setup.

The original heads on this motor were 72 7H1 heads, which were 1.96/1.77 valves. Cam lift was small in that application, tho. Weird.

Glad there are more "tree-fiddy" motors getting some love!

[242177P]

Nice seeing the 2.11 clear that small bore. As Squidward says,
deck clearance will change depending on casting used.

Now here's the $60,000 dollar question: at what point do you
sacrifice valve lift for compression? There's like 20cc worth of
difference between the late 6X-4s and early 17s (IIRC).

And if it's just some bowl blending, you could add a big valve
to a '69 47. There's enough variables to make one's head spin,
but it's all so very intriguing.

[srmmmm]

Originally Posted by 242177P

Nice seeing the 2.11 clear that small bore. As Squidward says,
deck clearance will change depending on casting used.

Now here's the $60,000 dollar question: at what point do you
sacrifice valve lift for compression? There's like 20cc worth of
difference between the late 6X-4s and early 17s (IIRC).

And if it's just some bowl blending, you could add a big valve
to a '69 47. There's enough variables to make one's head spin,
but it's all so very intriguing.

Going to a 4.25" stroke, the 6X-4 heads gave me a comfortable CR of about 9.3 to 1. I've had no issues running 92-93 octane in it as a result.

[Squidward]

Originally Posted by 242177P

And if it's just some bowl blending, you could add a big valve
to a '69 47. There's enough variables to make one's head spin,
but it's all so very intriguing.

That's what I had done to the 47's on the 400 in my Lemans - big valves. Paul Carter did those heads, and said his previous testing showed an increase in flow numbers.