Piston to Cylinder Head Clearance

[Blue Z]

Hi Guys,

 

I am currently in the process of building my L28 and I'm interested what the minimum piston to cylinder head clearance that people have run?  If you could also provide KW and maximum timing during load that would also be really interesting?

 

The build that I working on is N42 head with flat top pistons(+1mm), I am currently looking to weld the combustion chamber to enhance squish, similar to what they did in How to modify Nissan / Datsun OHC book. The book recommends a minimum of 50 thou piston to head clearance, however I have heard that this can be taken down to 30 thou.  Due to the fact that I will have a lumpy cam I will cut valve reliefs in the flat top pistons which will offset the welding on the chambers, my aim is to keep compression ratio about 12.

 

Any information would be appreciated.

BlueZ

[dat2kman]

Take into account the gasket thickness,

Measure a new one, then a used one, to guage amount it gets squashed once torqued/used.

Quite ok for a piston to protrude 10 or 15 thou, but at rpm, it all grows out further.