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Author Topic:   piston machine
motorsport 18
posted February 26, 2004 02:48 PM
ive recently bought a set of alum brodix track 1 heads for a mod motor and they are set up for a roller cam and was told i might have to machine the pistions down for the roller cam its650on the max side lift i guess its for valve reasons any one run into this i only have a 100 dome pistion 350 30 over

posted February 26, 2004 06:51 PM
It's not so much the dome of the piston that will be the problem, it is the depth of the valve pocket itself that quite often must be fly cut to gain the proper amount of valve-to-piston clearance.
This is quite common in higher HP applications or custom engine combo's.
The thing to remember is that the point at which the valve gets closest to the piston is NOT when the piston is at TDC. The point at which it gets closest varies slightly depending on the cam grind.
Shoot for about .100" on the exhaust and maybe .070" on intake. Those are off-the-top-o-my-head #'s. Maybe Steve H., or another engine guy can verify.
Many engine shops can fly-cut your pistons for you. They'd prefer to verify it by doing the mock-up assembly themselves, usually.


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