Valve spring ?

[richd]

You'll get valve float which would rob some power, not to mention the possibility that valve and piston may collide from the valve not retracting fast enough.

Here's the specs for spring pressure from the Ford manual:

Compression Pressure (Lb @ Length)
Intake 74-82 @ 1.78 to 211-230 @ 1.33
Exhaust 77-85@1.60 to 200-226 (doesn't say at what length, so maybe fully compressed? Non HO specifies 192-210 @ 1.05, maybe HO is at same length)

Free Length
Intake 2.02
Exhaust 1.79

Ah, I see that it says service limit is 10% pressure loss @ length. 100 lbs is close to 50% at short length.

Hope this helps,

Rich D.