[chiphead]

Check your results again. You changed the pushrod length .200" and the pattern did not change a whole bunch. Changing the pushrod length almost a quarter-inch should put the pattern way off the valve.

Are you setting up the test on the cam's base circle each time?
Are you rolling the motor 2 complete revolutions for each test?
What are you going to use for guideplates?

[ta man]

Agreed.Large pushrod change for a minor mill on heads?Don't overthink this.I've had milled heads kept same pushrods no problems.

[kenneth77]

yes i startet at base cam lobe,and did 2 rev on engine.im using stock pontiac guideplates that i had to modify to make them fit.

there is a big difference for stock to +.200 on the lenghts. the pattern moves from intake side ,to the exhaust side.

[chiphead]

Are you using the weak checking valvesprings, or the full-power valvesprings? Are you sure the checking pushrod is not distorting or bending when you do the test? Are you sure the lifter is not collapsing?

You usually change the pushrod length in the order of .030" to .090". .200" difference is huge! It shouldn't work at all....

[kenneth77]

im using full power valvesprings.what will couse a difference in wear pattern using light check springs vs full power springs?

[kenneth77]

how much preload should i add to the pushrod length?

rohads lifters

[kenneth77]

i measured again today and came up with a total lenght of the pushrod on 8.768".
then the roller rocker is approx center on valve stem at half lift.

my readings before was not good.


are you saying that i should not add any preload to the pushrod lenghts?
the lenght i came up with was with plunger pressed up against the retaining clip. when i screw down for preload

[ta man]

How much were your heads milled?

[kenneth77]

0,0040