sharptech

So I did a valve adjustment about 5k ago and so I figured I would check today just to see how they are. Well I let the car sit for 2 days so motor was way cold and poped off valve cover and all my intake valves were .06"-.07" I had set them at .08"... So I didn't touch them at all drove all day today and as soon as I got home I hurried and poped cover off again and with the motor super hot intake is .12"-.10".... exhaust went up as well. Does anyone know why its doing this I thought the clearence is supposed to be closer the hotter it gets. and further away the colder.

sharptech

bump for any answer?

sharptech

does anybody know?

R3DS2K

metal is softer when hot? besides you shouldnt be messing with it when its super hot..

2poor2mod

waiting for billman to respond

sharptech

my thoughts exactly

ZDan

Hot clearances are bigger than cold, but usually not by that much. On the Datsun, cold clearances are .008 and .010, hot .010 and .012. The aluminum head expands more than the steel valves when hot.

chris_barry

When the engine gets hot the alloy head expands and gets taller. The valves dont expand as much so the clearance increases.

One way of thinking about it is that the as the head gets thicker the valve gets pulled down relative to the top surface of the head.

The exhaust valves do expand with the head a bit more so they are generally set with more clearance.

Some race engines are built with almost no cold clearance and rely on the head expanding to introduce clearance. When they start to get difficult to start cold you know its time to redo the clearances.

Chris.

jyeung528

waiting for official answer...

sharptech

bump