Quote:
Originally Posted by steve25
Heres what I get from looking at the specs for the springs on these heads.
Closed = 117 lb
Open = 292 lb, but this was stated with what was the original cam that had .470 lift, which is not what the production 323 cam had.
The 323 cam only had .406 lift!
Now with no info on what the actual springs rates where my best guess is a open pressure with the .406 lift of 260 lbs .
This to me would be marginal with with the valve weight of even the 4.980 length valves, no less the longer heavier valves in the SD motor.
Just to make a comparison the 1968 428 HO motor had springs that provided 129 on the seat and and 272 open @ .414 .
What do you folks think?
Mike do you still have the stock springs to do a check on?
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I think the SD valves are 4.980 long. The exhaust valves are made from Inconal so they are fairly heavy. The intake valves have some mass due to their tulip shape. I don't think you need more than the factory springs to keep up with the RPM capabilities of the factory cams..... and the Super Duty 455 is an all around Bad Azz engine.