Cutting valve pockets into M30B34/B35 pistons

[szacsi72]

Hi guys,

Has anyone sucessfully cut deeper valve pockets into the mentioned pistons? How much material can I mill away? I know M30 pistons are quite thick - but I wonder: exactly how thick?

Thanks.

[Chimi-Changa]

Yes, local machine shop did my piano top 10:1's recently for valve relief with the 290 cam. Made a punch for center marking out of an old valve. Should be plenty of material...From my build thread in eye candy:

[szacsi72]

Thanks. Looks more than deep enough. I'm also running or well.. will be running a 290mm cam with 10.2mm lift from KM cams.

[Chimi-Changa]

Mine has Dblias 290 cam that has 11.0mm lift

[szacsi72]

Mine has Dblias 290 cam that has 11.0mm lift

Cool, then I'll be more than fine. Altogh I'll have the block shaved 0.4mm and the head 0.3mm.

[Chimi-Changa]

^Stock gasket, thicker stock gasket or MLS?

[szacsi72]

Stock gasket.

I don't like MLS gaskets. Will bump my compression ratio up by .8, and the pistons will still not interfere - the only question is, of course, the valves

[szacsi72]

Finally getting the time do cut the valve relief pockets, before taking the block to the machine shop...

Yes, local machine shop did my piano top 10:1's recently for valve relief with the 290 cam. Made a punch for center marking out of an old valve. Should be plenty of material...From my build thread in eye candy:

Do you remember how deep your pockets are?

I'm thinking 3mm on the intake side and 2mm on the exhaust side.

[Chimi-Changa]

With my setup ( 290 cam, believe head decked once- still strong witness markings, block not decked, b35 valves and springs, factory gasket) My machine shop looked at the kiss marks on the top of my pistons and cut pockets with 1mm clearance for sides, and 1.5mm for intake and 2.3mm for exhaust clearance. I do not know the actual depth, here is the pic he drew explaining them the space needed:



He made me this punch out of an old valve, and I used that with an empty b34 head to mark one piston both sides.

[szacsi72]

Awesome, thanks!
Interesting that they added more clearance to the exhaust side.
I'll measure the original clearances before cutting anything, that's for sure.