Valve to cylinder wall clearance,Shrouding Question?

Erland Cox · Post by **Erland Cox** » Sun Oct 12, 2008 7:09 pm

There are both benefits and losses with relieving the cylinder. A chamber full off little crevices does nothing for the flame travel. The surface to volume ratio should be as small as possible. I know of stock racers using 2 bolt blocks in order to get rid off the relief that 4-valve blocks have. Beyond that you need at least 12% of the intake valves diameter in clearance to the cylinder wall at full lift. Erland.

blwilliams · Post by **blwilliams** » Sun Oct 12, 2008 11:54 pm

cboggs wrote: Web guys, .. ;-(

Plus I haven't had time to write any new tech articles, .. I'd really like to though. Too busy running a shop and porting.

Curtis, your tech page used to have a percentage number of bore diameter to intake valve diameter.
That is what I was looking for last week.
Thanks for all your information and time you donate to these forums.

e-tach · Post by **e-tach** » Mon Oct 13, 2008 12:29 am

blwilliams wrote: percentage number of bore diameter to intake valve diameter.

Here ya go:

52-52.5% of the bore for Wedge heads.
53-53.5% for Canted valve heads.

GrannySShifting · Post by **GrannySShifting** » Tue Jan 06, 2009 8:47 am

How is an offset dowel going to work on SBC unless its somethine like the CFE siamese port head like Ford or LS1?

They are EI IE EI IE, dowel would cheat half cylinder right and half wrong? Unless you do that for another reason?

Not sure how BBCs are pair up