Piston to Valve Clearance

this is from the Vick auto site
SOHC 42-82 82-42 high performance camshaft. 304 degrees of duration, 84 degrees overlap, 10.6 mm lift
 
so today i wasnt able to do much with the car but i was able to try to retest the piston to valve because i think when i installed the cam housing i prematurely squished the playdoh, when i did this i was able to get the piston at top dead center and the cam than put the belt on but as soon as i tension the belt the crank jumps to about -10 degrees so than i timed it +5 figuring it would jump down again when tensioned but this time it stayed dead on +5, so it this point i was very confused so i put the crank at +10 and cam tdc and when i tensioned the belt it didn't move it stayed at 10 than i tried at around 3 and it again jumped to -10 as soon as i tensioned so at this point im tired confused and annoyed so i turned the engine over to see if the out come was at-least a little more favorable than last time and it kinda was at-least this time there was clearance below is the picture of the playdoh from cylinder 4 i cut it so u could see the cross section, the exhaust valve is the deep indent and the intake barely hit the playdoh

DSC_6211.jpg


DSC_6212.jpg


DSC_6213.jpg
 
OK, these look about correct.

I was going to suggest removing the cam housing, installing two cam buckets with identical sized shims in cylinder# 1, then rotate the cam until both cam lobes are pressing down the buckets, observing/measure the bottom side of the cam bucket and rotating the cam until both intake and exhaust buckets protrude from the cam housing with equal height.

This is a test that could be done without using a dial indicator, degree wheel and getting into the complexities of setting up cam timing.

This will give an rough estimate of split over lap would be located and where the cam could be set with the pistons at TDC for the play dough test.

An adjustable cam cog would be needed to zero this in.

Anyway, It looks like the current play dough test is within the range of running engine. To get optimum performance, get the adjustable cam cog and spend a bit of dyno time.


mike3487 said:
so today i wasnt able to do much with the car but i was able to try to retest the piston to valve because i think when i installed the cam housing i prematurely squished the playdoh, when i did this i was able to get the piston at top dead center and the cam than put the belt on but as soon as i tension the belt the crank jumps to about -10 degrees so than i timed it +5 figuring it would jump down again when tensioned but this time it stayed dead on +5, so it this point i was very confused so i put the crank at +10 and cam tdc and when i tensioned the belt it didn't move it stayed at 10 than i tried at around 3 and it again jumped to -10 as soon as i tensioned so at this point im tired confused and annoyed so i turned the engine over to see if the out come was at-least a little more favorable than last time and it kinda was at-least this time there was clearance below is the picture of the playdoh from cylinder 4 i cut it so u could see the cross section, the exhaust valve is the deep indent and the intake barely hit the playdoh
Click to expand...
 
so i found a source online that said that 3mm was necessary for the intake clearance and 4mm for exhaust which is .118 and .157. i tested my clearance again and on the intake the valve didn't even ht the playdoh again and the exhaust measured .14 on all this was all at +5 degrees on the crank
 
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