Piston to Valve clearance

[toletero]

Wazup guys , I just order a new cam kit at MOTORSPORT AUTO and they told me that I need to check the Piston to Valve clearance , now can anyone tell me how can I do this I have an idea how to do it , but I was hoping that someone have used the kind of cam I using , The setup that I have in my car is stock , stock pistons , its not been rebore , an E31 head L24 block . The cam is a 560 lift and 290 duration , Im taking my head to the machine shop so I can get a better or higher compression ratio than stock , now can anyone help me here I'll apreciated , thanks ...

[2ManyZs]

Well, the only way I know how to check the valve to piston clearance is to remove the head, place something like plumbers putty on top of the piston, replace the head, and crank it over by hand. When you put the head on be sure to use the same thickness of head gasket you are planning on using and torque the head to the proper specs. Then remove the head, peel the putty off the top of the piston and measure the thickness at the thinnest place. This will give you the valve to piston clearance. I beleive there is probably a special putty for this but don't know the correct name for it.

They need to know the valve to piston clearance after any head work is done. If the head is shaved it reduces the clearance and they are trying to determine if the cam lift will cause the valve to hit the top of the piston. When the head is shaved you will also need to shim the cam towers the same amount that the head is shaved to correct the cam timing.

Since you say you are going to have the compression ration changed with head work, this will mean shaving the head.

BTW, if the head is straight you could save yourself a little money by using a thinner head gasket instead of paying for the machine work to shave the head. There are two different thicknesses available besides the stock thickness. MSA has them. With the E-31 on the L-24 you should have about 9 or 9.5:1 so in order to keep from having detonation problems you should try to keep the compression ratio at 10.5:1 or a little lower, you should come close to this with just the thinner gasket, but to be sure I'd have to look in the engine calculator to see what it would turn out to be. A lot depends on the overbore (if any) and if you are using the stock flat top L-24 pistons. If you haven't looked you can download the L engine calculator from the Downloads section here on the site and do a little experimentation on your own before you start forking over any money.