I only see a problem when it's a real racing engine with the cam
operating the valve directly and
expensive light weight components.
Example: A 3L 4 valve V-8 N/A would probably be happy with 20-40 lbs.
seat pressure. It doesn't
have a big bunch of machinery rattling around trying to bounce a valve
open like a SBC.
I shimmed my stock Kawasaki valves .040 and that increased the seat
pressure to the point that
I couldn't open the valves with my fingers. Thumbs - yes, fingers - no.
It made me feel better!
Max boost was 22-24 PSIG at Bonneville (4216', DA 7500').
Bryan
drmayf wrote:
> Elon wrote:
>
>
>> Yes, he is right. A 2.02 intake valve plus 15 psi boost needs about 48 lbs
>> to be added when SEATED. -Elon
>>
>> (snip. . . ) he immediately is adding spring pressure, valve area X boost,
>> for a cam change on a motor built by someone else. I'm not sure he's right
>> about this. Thanks, BJ in the Bean
>> _______________________________________________
>> drmayf@mayfco.com
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>>
>>
>>
> I am sort of ambivalent about this. Here is why. On the intake stroke
> the vlave is open so no added spring pressure is needed. On the
> compression stroke, no added spring is required because the cylinder
> pressure overcomes that. On the exhaust stroke, for a turbo there is
> pressure in the cylinders even after the stroke is completed, so high
> possibility that bo added sprng is needed then either. And of course,
> on the power stroke the chamber/cyliner pressures are fairly high so no
> added spring is needed then either. So while, I don't think it hurts to
> add a pound or two to the spring rate, the very short times where valve
> overlap might occure and need spring pressure increase is really a short
> timep period. Really short. That's fora turbo car. On a supercharged
> car, the idea is to remove the burbed junk as rapidly as possible and
> with as littl eback pressure as you can possibly have. So the end of the
> exhaust stroke might need some added rate, but the othere seems to
> pretty much follow the same reasoning?
>
> mayf
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