How would you measure piston-to-valve clearance with a dial gauge and stand? Using the modeling clay makes sense.. this doesn't. I'm probably missing something really obvious! Plus, how does the degree wheel fit into all of this?

Also, here's an easy one: It makes no difference if a degree wheel is used on a V8 or V6, right?

Thanks!


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-Tom P (Hot rodded 1986 Firebird 2.8l)

 

It makes it easier if you have some soft springs. That way you can turn the motor over at very small increments.

Put the light springs on the #1 cylinder. Put the dial indicator on the valve spring retainer. Make sure the cam is on the basecircle.

Depress the dial indicator until you have about .4" of the dial indicators range used. Now Zero the dial indicator.

Rotate the motor through the overlap cycle (at about 10 degree intervals) and press the retainer down at each 10 degree point. See how far the dampener goes before it contacts the piston at the valve reliefs. That is your piston to valve clearance in thousands of an inch.

V6 or v8 does not matter.
I think thats it. If i have misquoted something this group will surely point it out.

 

Wow! Thanks! So it's not the actual camshaft that moves the valve for checking, it's me pressing on the valve? Now, I guess if I find out I've got zero clearance, that's when I stop turning the crankshaft, right?
Then, would I spin the crank "backwards" to find out at what range of degrees the interference is?

Er, wait... how do I know how "far" is okay? Seems like I could push the retainer (as in valve stem?) down as far as I want to, and always hit a piston... or, does it not matter, just so I know the clearance?

Thanks!


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-Tom P (Hot rodded 1986 Firebird 2.8l)

 

Yes, you are going to manually determine how much is left after the cam puts it at the closest proximity.

Quote:

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Now, I guess if I find out I've got zero clearance, that's when I stop turning the crankshaft, right?

Yep . Even though it's not likely. In most cases, if that has happened, the dots were not correctly aligned up on the timing marks.

Quote:

<font face="Verdana, Arial" size="2">
Then, would I spin the crank "backwards" to find out at what range of degrees the interference is?

Er, wait... how do I know how "far" is okay? Seems like I could push the retainer (as in valve stem?) down as far as I want to, and always hit a piston... or, does it not matter, just so I know the clearance?

You need about .1 inch between the exhaust valve and the piston and at least .090" for the intake.

If its over .1 inch (one full rotation of the dial indicator), you are good to go.

 

Thanks! I kind of want to tear my engine apart just so I can try this! Is more clearance needed for the exhaust valve because it expands more with heat?


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-Tom P (Hot rodded 1986 Firebird 2.8l)

 

Yep, thats the biggest part of it.
I would not do it just for grins though..

 

(laughs) Thanks again!

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-Tom P (Hot rodded 1986 Firebird 2.8l)