Piston to Valve Clearance with oversized valves on M20

[dstevenson]

So I got my M20 head back from the shop. What I run is a stock M20 bottom end and a mild 272/272 cam (one bump up from the OEM 264/264). This setup had no issues with piston to valve clearance. When I got the head back they told me the valves I gave them were larger valves. These are SuperTech valves and they do make them 1mm oversized. I will measure these again next to the old ones.

So assuming both intake and exhaust valves are both 1mm over, is there a chance that these valves will be to wide and overshoot the valve pockets on the top of the OEM M20 pistons ?

Thanks

[Panici]

So I got my M20 head back from the shop. What I run is a stock M20 bottom end and a mild 272/272 cam (one bump up from the OEM 264/264). This setup had no issues with piston to valve clearance. When I got the head back they told me the valves I gave them were larger valves. These are SuperTech valves and they do make them 1mm oversized. I will measure these again next to the old ones.

So assuming both intake and exhaust valves are both 1mm over, is there a chance that these valves will be to wide and overshoot the valve pockets on the top of the OEM M20 pistons ?

Thanks

I'm sure others will chime in, but if it were me I would want to verify for myself with Plastigage.

[ForcedFirebird]

I would clay to be sure, but +1mm valves aren't going to protrude much more than stock since the valves are only 22° from vertical.

[digger]

the stock pistons have a intake pocket diameter of D44mm so D43mm valve is too small to reliably ensure the radial clearance is fine, you need minimum 1mm to be safe, the axial clearance is unaffected. the exhaust pocket is D39 so D37 valve is a borderline pass

I'm sure people have risked it before id break out the die grinder or make a fixture to machine them

[TobyB]

Me, I'd carefully clay it, and then if digger's 1mm isn't everywhere, make sure that it is.

t
has gotten it too tight, and has coffee tables to prove it.

[ForcedFirebird]

Me, I'd carefully clay it, and then if digger's 1mm isn't everywhere, make sure that it is.

t
has gotten it too tight, and has coffee tables to prove it.

OP actually phoned me, I told them how to use clay and the old gasket.

[TobyB]

Awww.... but the blocks make such nice furniture...

t
still feels stupid about that one.