RS Motorsport :: Classic Speed Restored

With a N/A yb head at what amount of valve lift do you need to have valve pockets when the pistons are flat top and at deck hight?

Depends how big the cams are as they'll need a pockep of some description as well as a protruder if you want any compression

This is one of mine

Hey David have you got a photo of the combustion chamber

Danny, not sure possibly not, I will have a look.
David

Hey Dave why did they butcher the piston crowns as there is compression to be gained leaving them alone


Danny

Neil I have a set of pistons for sale if your interested

Belly 0409893491

DM, I can't answer that.
It was a recommendation of the piston supplier to "radius" all the edges, after the first set failed $$$$$$$.
Also now running 110 RON fuel @ $8 + per ltr
YB's are $ big time, but once your hooked, it's game on. DM you have many work customers with the same problem
The power buzz is worth the $ pain !
David

Belly,
Your NOT going "Turbo" are you ?
David

David sharp edges are not the issue and should not have been the reason they failed as I've run some over the top sharp edges and I know of others and it was the norm in super tourers as the consensus of it being a bit of a wives tale of poor tuning
Have you got any photo's of the piston failures and the combustion chambers as the compression ratio wont be an issue

Danny

These are the Burton sourced 11.1 Accralite pistons I'm planning on putting in my N/A Cosworth.
Previously had Mahle flat tops with approx .040 valve reliefs. Nowhere near enough compression with them.

If you look closely at the Mahle piston you can see here a valve has just touched the piston. Luckily it didn't do any serious damage to the valve. I won't mention the name of the business that adjusted the cam timing when dyno tuning the engine. And this was with BD14 cams with stuff all lift or duration.

Chaps,

What Dan is not mentioning here, is he has the chambers welded up.

RM