Valve Pockets-N/A Engine

by **Neil S** » Sun Aug 08, 2010 10:07 pm

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?

by **Danny M** » Mon Aug 09, 2010 5:33 pm

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

by **escortmk1600gt** » Mon Aug 09, 2010 5:50 pm

This is one of mine

by **Danny M** » Mon Aug 09, 2010 7:10 pm

Hey David have you got a photo of the combustion chamber

by **escortmk1600gt** » Mon Aug 09, 2010 7:18 pm

Danny, not sure :cry:

possibly not, I will have a look.
David

by **Danny M** » Sat Aug 21, 2010 11:57 pm

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

Danny

by **Belly** » Sun Aug 22, 2010 8:35 pm

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

Belly 0409893491

by **escortmk1600gt** » Fri Sep 03, 2010 9:15 pm

DM, I can't answer that.
It was a recommendation of the piston supplier to "radius" all the edges, after the first set failed $$$$$$$. :^o

Also now running 110 RON fuel @ $8 + per ltr :evil:

YB's are $ big time, but once your hooked, it's game on. DM you have many work customers with the same problem :wink:

The power buzz is worth the $ pain !
David

by **escortmk1600gt** » Fri Sep 03, 2010 9:17 pm

Belly,
Your NOT going "Turbo" are you ? [-X

David

by **Danny M** » Sat Sep 04, 2010 1:25 am

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

by **SportsSedanSteve** » Tue Jan 04, 2011 6:34 pm

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.

by **Roger Miller** » Sun May 15, 2011 9:25 am

Chaps,

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

RM

Valve Pockets-N/A Engine

Valve Pockets-N/A Engine

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