BritishV8 Forum

Does anyone have any experience with stock valves at extreme (6500-7000) rpm?  Curios about the strength of the necked-down valve stems.

Why would you ? Stock valve sizes will likey flow/power peak, below 6k ?

Actually, Art, I am using larger valves from an older 225 Buick. They are the largest valves that will fit in the heads without installing larger seats. They are also about maximum size for the ports with reasonable porting done. The stems are necked down and use the same keepers. Therefore the question. Thanks.

Nice. Some flowbench data would be good.  

The question about rpm is critical to the engine I am building at the moment.  There are, unfortunately, a number of things to be determined that depend on the rpm available. I have generally, within reason, selected components that are capable of operating at reasonably high rpm. My target horsepower is 425.  Somewhere, rattling around in my head, is the idea that I will probably need around 6500 rpm limit. Now I'm an old guy and a fairly conservative driver, but when I push the pedal down, I like to see results. Hopefully, the pair of KKK turbos will give me a fat torque curve. I have spoken to Dan Jones about designing a roller cam to do the job.

I would rather not be looking for custom valves. Thanks.

425 "actual" hp., is a LOT, for an RV8 !  Say perhaps 20+ lbs, manifold pressure ? Care to describe your build plan ?  Good Luck, roverman.

The turbos are from a 996 that is 3.6l and makes 420 "actual" horsepower at 6000 rpm and 10.6 lb. boost. They have 4-valve heads, but I will be able to run a more aggressive camshaft. I also want a little more rpm to work with. Hence the original question. How many rpm will new stock valves handle?

IMHO, I would know what the RV8 heads flow, from .05" - max. lift. Buick Grand National/turbo valves, "may" have better suited metalurgy. I still suspect, with reworked RV8 heads, you will need close to 20 lbs. manifold boost. Understand, with ported TA heads, you would need much less boost to equal the output. You have a rotating assembly, that will sustain this-reliably  ?  Good Luck, roverman.

It's a balancing act, enough spring to not float the valves vs enough lift to fill the cylinders and then there's the life of the valvetrain to consider, etc, etc. I've gotten 7 grand with less than 120 lb seated pressure...

Jim

Jim, what kind of valves were you using?

Buick 215

That's the answer that I have been looking for. Thanks!

No problem, hope it helps.

That was with CC's hottest SBB hydraulic which they don't offer anymore. The springs were the ones they sold with that cam. Back about 1985 or thereabouts.

Jim