valve float, rpm limitations

[Eric Walter <ewalter@domain.elided>]

Tom Mandera wrote:

> 
> Would someone describe what happens during "valve float".. some quick
> calcs shows I had my '72 Scout II w/ 304 around 4800 or 4900rpm before 
> -Tom

Valve float occurs when there is insufficient valve spring pressure to
fully close the valves at high rpms.  Assuming IH's valve springs are
comparable to other makers (I think around ~100-200 lbs. closed) you
shouldn't have any problem (well, no valve float anyway) till 7500 rpm.
A buddy of mine put 400 lb. springs in his 396, can you imagine how
horsepower it took to turn that camshaft!
Some other high rpm problems: 
Fuel pump has the same problem as valves, spring doesn't return the arm
fast enough.
Piston speed, the top of the piston detaches from the rest, basically
snatched off by the quick reversal of direction. Long stroke motors
achieve max speed before short stroke motors, cast pistons before
forged.
Main journal surface speed, bearings gall after a certain speed. This is
why small journal 327's are more desirable than large joural ones.
Oil may not be able to drain out of heads and lifter valley fast enough,
lowering oil level in pan.
Other valve train problems, timing chain stretch, cam twist, push rod
flex, rocker shaft flex...
Keep it under redline,
Eric