[Land-speed] Finally an LSR Question

[Bryan Savage]

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
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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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