Piston to valve clearance? - Team Camaro Tech
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post #1 of 7 (permalink) Old Nov 15th, 02, 10:57 AM Thread Starter
 
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Location: Hansville,Wa. USA
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With the heads mounted to the block how can I figure piston to valve clearance?
AFR 195 heads, (new cam, 506 lift), 10.1 c.r. domed pistons.
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post #2 of 7 (permalink) Old Nov 15th, 02, 11:12 AM
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This is BY FAR not a technical explaination and is probably not complete:

Put a blob of modelling clay on top of one or more of the pistons, torque the heads to specs with the gaskets that you're going to use, rotate the engine until that piston or pistons has run through full intake and exhaust, pull the heads and see how deep the impressions are. You can then measure the clay at the depressions by either using a dial indicator or ruler and comparing the measurement from the deck surface to the piston surface compared to the deck surface to the deepest depression in the clay, and figuring out the difference.

I've never done it, but I've read a lot of stuff about checking the clearances and this is only one method.
Correct me if I missed anything....

[This message has been edited by HwyStarJoe (edited 11-15-2002).]
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post #3 of 7 (permalink) Old Nov 15th, 02, 11:22 AM
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post #4 of 7 (permalink) Old Nov 15th, 02, 04:42 PM
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One other thing, if you are running a hyd. cam you will need a solid lifter to check. A hyd. lifter will not give you a true reading. I took a hyd. lifter apart and made it into a solid by removing the internals and stacking washers in the body. once that was done I put the push rod cup/seat back in and replaced the snap ring. Of course you could just use a dial indacator and push the valve down the proper amount and then measure the clay.

Royce
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post #5 of 7 (permalink) Old Nov 16th, 02, 02:30 PM
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Eric
 
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Whatever you do, DO NOT use a head gasket when you do the modeling clay method. If you do you just wasted a perfectly good head gasket for no reason. Just put everything together WITHOUT a head gasket and measure the thickness of the compressed clay on top of the piston. Then just add the compressed thickness of the head gasket (from the packaging) and you have your number.
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post #6 of 7 (permalink) Old Nov 16th, 02, 11:13 PM
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the clay trick does work well, but IMO, the best way to do it is with a light spring, installed in place of your valve spring and a dial indicator on the retainer. this gives you real accurate readings of v to p which is really important if they are going to be close. the clay is good for a rough estimate, it's been done that way for years, but if you want to know for sure and are running close, use a light spring and a dial indicator. also, as eric said, leave the gasket out and just figure that in to the equation, using its compressed thickness. good luck! edit; after re-reading your post, i'd be very surprised, even amazed, if you don't have a ton of clearance w/ that cam, so clay will probably do, but then again, it's good to learn how to do it the most accurate way.

[This message has been edited by 68rs406 (edited 11-17-2002).]
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post #7 of 7 (permalink) Old Nov 18th, 02, 02:21 AM
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I prefer the clay method. It gives you a picture of what is realy going on and were. The valve spring method works great but it only gives you a reading at the closest point. They clay shows how close you are to walls and plugs.
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