What is valve lash? is that the clearance when doing a valve adjustment? thanks
Luis

 

Valve lash is how long the rocker arm sits on the cam lobe. Using slight adjustments in vavle lash can vary total duration and cam overlap.

Increasing valve lash, which would make smaller vavle clearance, increases cylinder pressure in low and midrange rpms, closes the intake valve sooner, and reduces cam overlap and total cam duration.

Reducing valve lash, which would make a larger valve clearance, will do the opposite of increasing.

 

i'm sorry if i'm not just getting this, but can i get some clarification? if valve lash is the amount of time the rocker sits on the cam lobe, then when you increase valve lash shouldn't the duration on the cam be increased too? if so, then increased valve lash means more time on the cam which would open the valve sooner, close it later, and increase overlap. am i missing something here?

 

Increasing lash puts the rocker farther away from the cam lobe, which means the valves will not open as far, thus decreasing lift and duration. If you set it too loose, the valvetrain will become very noisy. If you set it too tight (very small clearance), the valves might not close all the way and you will lose cylinder pressure. Always check and adjust valve lash when the engine is bone cold. The specified lash measurement is listed on the emissions sticker on the underside of your hood. I think it's .006-.007" intake, and .007-.008" exhaust for a GS-R.

 

a snug .006 on the intake side(.007 should not fit)
and a snug .007 on the exhaust side(.008 should not fit)

thats what i do on my gsr.

 

I understand where you're coming from here... but slight differences in valve lash shouldn't affect overlap enough to be noticeable (w/i spec)... (Am I alone on this ?)

X2

 

I agree, but also valve lash is the clearance between the rocker arm and cam lobe, not the length of time the lobe sits on the cam.