CVH Oil vapour pressure

[stinkysteve]

Hi folks,

Hi Dave Baker - Hopefully

I've got a 1600 CVH with a Puma Race engines big valve head. Solid lifters, High lift camshaft, twin 45's, etc. i like to think it's a well built engine. (assembled by Jeff Wilson at HWR)

I run it in the northern saloon car championship and testing on Wednesday resulted in a 1.41 round Croft. Not too shabby for a N/A 1600 but i need to shave a couple more seconds off to be at the front.

Anyway, shaving time off isn't related to this post, as the engine runs well enough, it just seems to have very high oil vapour pressure.

The crankcase breather vents to the rocker cover, and the rocker cover to a catch tank.

It's always blown vapour through the breather coming out of the catch tank, but on wednesday it was blowing through the oil filler cap (a screwed down type on a motorsport rocker cover)

Is such high vapour pressure normal? should i be worried? and is there anything i can do/should do/ should not do to address his?

Would a restrictor in the breather pipes help?

It doesn't use much, if any oil, and runs well.

No need to panic?

Any advice will be gratefully recieved.

Dave, have you moved to Scotland yet?

Cheers, Steve

[powerstroke]

well its the result of combusion presure going past the rings!! high compression and or high revs/loads will make this worse all you can do is compare it to other simalar engines and if its worse for blow by then its a strip down and check clearances and or for broken rings , resticting the breather would be a bad move as the presure would go up in the sump /rocker cover and maybe blow a oil seal or gasket out , dont know much about the CVH engine but some times if a lot of oil is coming out of the breather into the catch tank its the crank wipping it up, then the blowby carrys it out of the breather, the fix can be a windage tray in the sump or just running with slighty less oil does the trick assuming you have a wet sump....

[stinkysteve]

Thanks Powerstroke, appreciate the post.

The rings are new, the engines just been rebuilt. Honestly, the more i think about it, i think all my CVH's have had the same issue. (I've had 4 engines with new rings built up over the last 3 years and they've all shown high vapour pressure)

There's not a lot of oil making it to the catch tank. Any oil whipped up by the crank heads to the rocker cover first and then that breathes to the catch tank.

Yes it's wet sumped, and has good baffling. Never herd of a windage plate but presume i believe i know what it is.

I guess i could do a compression test on the engine easily enough, just to confirm all cylinders are equal and one doesn't have dodgy rings. But by the way it was going last week i doubt i have a problem.

Any CVH experts/users experience the same?

[Pumaracing]

stinkysteve said:

Hi folks,

Hi Dave Baker - Hopefully

Dave, have you moved to Scotland yet?

Cheers, Steve

Yes and haven't had internet access for weeks hence my disappearance from here. I've never had a blowy CVH that had a properly built bottom end and can't see any other obvious reason for your issues.