hello, i put L16 valve in my h10 head 38\33. I've checked the inlet valve to cylinder wall clearance and its good. the exhaust needs opening though(about 1.5 mm wider).

now i also have a .423" lift cam i was trying to figure out if this could clear with stock dish .040" over pistons, to do so i need to find out what the stock piston to valve clearance is, dose anybody know? also how far dose the exhaust valve protrude into the block deck so i know what depth to cut out of the stock valve reliefs?

Put the head on with the gasket a layer of plastecine ontop of the piston with some light oil so it wot stick to the valves

Rotate the engine with cams pushrods in obviosly and this will leave a contact area on the plastecine

Take the head of and you can cut the contact area in half and measure the depths to determine how much you need to cut the piston tops for clerance


To make flycuts u can use a circle sanding pad that you can glue to the head of the valve and put a drill on the stem and cut away at the pistons slowly

Probably beter methods but has worked for me in the past

i was going to try that method but i need to do the ex to block clearance first.

Dunno what stock clearance is, but 0.035 inch is safe.

for the valve to block clearance the easiest method i think (probably not the right method) would be to buy those very light valve springs that you use to dial cams in with.

then open up the valve (with head on block bolted down with head gasket) to the max valve lift including rocker ratio etc and see if it contacts the block if not keep going until it touches and read on the dial indicator how far it goes down until contact and find the difference and see if the clearance is sufficient

allowing extra for heat expansion etc etc.

ive never personally done this and im thinking out loud so i would get others input on it.

stock A12 blocks already have notches in them for the valves not sure if it would be sufficient for you bigger valves and greater lift.

I used one of the springs from the rocker shaft (had a bunch of extras) when checking the clearance. I believe the clearance spec I got was .040 with the head gasket removed which would work out to 2mm (fel-pro gasket is 1.2) I used some silly putty style stuff that my son had lying around for years. once the valves put indentations in the putty I cut it down the center and measured.

Also try this manual it has some good info I what may need to be done to the block.


http://www.datsuncherry.ch/PDF/Rennteile75.pdf


Tom

Good info. It says

Quote:

that is 0.039 to 0.079 inches.

I'll definitely try that, thanks everybody! i just have to cut my valves down first.