This might be a dumb question, but I am confused. I know I need to check pushrod length and piston to valve clearance on the new motor. Which one do you do first? I realize that you have to have the entire valvetrain assembled to check piston to valve clearance, but if you change pushrod length, won't that change the piston to valve clearance measurement? Maybe I am just confused and not picturing this correctly. :confused: Can somebody give me some ideas about which one I need to check first?

Originally posted by THE DUDE:
This might be a dumb question, but I am confused. I know I need to check pushrod length and piston to valve clearance on the new motor. Which one do you do first? I realize that you have to have the entire valvetrain assembled to check piston to valve clearance, but if you change pushrod length, won't that change the piston to valve clearance measurement? Maybe I am just confused and not picturing this correctly. :confused: Can somebody give me some ideas about which one I need to check first? HI Mark,
One will have almost nothing to do with the other.
The valve will still move very close to the same amount with bad geometry especially on overlap where the pistons & valves like to get close.
The ex will be closest at about 10 degrees before TDC & the intake about 10 after so don't just check it at TDC, check from about 20 before to 20 after on overlap.

Thanks Dude for asking this question, I can scratch it off my lonnng list smile.gif
Mike,is it ok to check piston valve clearance when mocking up the engine. I mean when the pistons have no rings yet and may rock in the cylinders too much to give an accurate measurement.

Originally posted by blumont:
Thanks Dude for asking this question, I can scratch it off my lonnng list smile.gif
Mike,is it ok to check piston valve clearance when mocking up the engine. I mean when the pistons have no rings yet and may rock in the cylinders too much to give an accurate measurement. Yes in most applications it is no problem.
Every shelf piston I have seen has the notch bigger in diameter than the valve by a bunch & this is where you can get into trouble with larger valves or custom pistons
I like about .100" minimum dia. larger notch or .050 clearance than the valve you are running
When you start getting close to the notch edge in the piston then you need to be concerned with piston rock ;)

Jerry,
I edited my last post as I meant to say .050" minimum radial clearance which would be .100" larger diameter notch not .050" dia which would only be .025" radial clearance graemlins/clonk.gif

just like a machinist, right down to the micron! smile.gif keep up the good work Mike.

Once again, thanks Mike graemlins/thumbsup.gif