Piston to valve clearance before installing cam - Team Camaro Tech
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post #1 of 10 (permalink) Old Feb 25th, 07, 04:00 PM Thread Starter
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Dave
 
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Piston to valve clearance before installing cam

Is there a way to calculate (estimate) piston to valve clearance before I have the cam installed? Is there a calculator out there?

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post #2 of 10 (permalink) Old Feb 25th, 07, 05:10 PM Thread Starter
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Dave
 
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Re: Piston to valve clearance before installing cam

...obviously using assumptions for cam lift and rocker ratio

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post #3 of 10 (permalink) Old Feb 25th, 07, 06:04 PM
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Re: Piston to valve clearance before installing cam

I'd think that it would be VERY hard to figure. Possible I suppose, IF you know exactly what the cam events and lobe profile are, but you'll never get the lobe profile unless you map it out your self, and if you have the cam to map it, why not just slide it in?





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post #4 of 10 (permalink) Old Feb 25th, 07, 06:24 PM Thread Starter
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Re: Piston to valve clearance before installing cam

Quote:
Originally Posted by JimM View Post
why not just slide it in?
I don't have the cam yet, so I want to figure out how much valve lift I can go with before I order it. I'd hate to get the cam and then determine there's not gonna be enough clearance.

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post #5 of 10 (permalink) Old Feb 25th, 07, 06:45 PM
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Re: Piston to valve clearance before installing cam

This indeed would be a good calculator. Seems like if you know all the specs, it could be done.

Robert

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post #6 of 10 (permalink) Old Feb 25th, 07, 06:55 PM
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Re: Piston to valve clearance before installing cam

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Originally Posted by rojo View Post
...Seems like if you know all the specs, it could be done.
Problem is it's more than just specs. The valves and pistons typically come their closest at 20-30 degrees before (intake) and and after (exhaust) top dead center. You could pull 4 standard profiles with 280 advertised duration (magnum, XE, hydro roller, mech roller) and get VASTLY different measurements depending on how quickly the valves are coming off the seat.





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post #7 of 10 (permalink) Old Feb 25th, 07, 07:40 PM
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Re: Piston to valve clearance before installing cam

Quote:
Originally Posted by JimM View Post
.....You could pull 4 standard profiles with 280 advertised duration (magnum, XE, hydro roller, mech roller) and get VASTLY different measurements......
So that means we really don't have all the specs. Right? Wrong? These cam co.'s surely know even though the info might not be accurately advertised.

Robert

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post #8 of 10 (permalink) Old Feb 25th, 07, 08:25 PM
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Re: Piston to valve clearance before installing cam

There are so many variables to this, more than cam specs, it's better to measure. Better safe than sorry.

Variables include: deck height, milled heads, compressed head gasket thickness, vavle size, pistons, how the pistons are clearanced ('eyebrows') for the valves.

With all of these variables, it wouldn't take much to be off, just a little. I can't think of anyone that would want to take on all that liability to develop a calculator.

Steve
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post #9 of 10 (permalink) Old Feb 25th, 07, 08:31 PM
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Re: Piston to valve clearance before installing cam

Good start on the variables list. Any more?

Robert

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post #10 of 10 (permalink) Old Feb 26th, 07, 05:02 PM
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Re: Piston to valve clearance before installing cam

I just put a voodoo in my 454. Pretty knowledgeable people said that I should have enough P/V clearance to drive a truck through. Guess what? Not even enough to get the spare tire through!

Lift has really nothing to do with P/V, its the overlap and other things. The Voodoo cams have such an aggressive intake valve that it actually almost hits the piston while chasing it down on the intake stroke. Closest was at 5*-10* ATDC.

Bottom line is check. Get your cams from Summit, so you can return them w/o an argument if needbe.

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