earmuffs

Can someone please explain the clay method to check piston to valve clearence. Do i need a solid lifer and torque the rockers? then rotate the crank and measure how thick the clay is?

RARON455

iTrader: (35)

Yes, you need a solid lifter,,, OR a very light spring. And you torque the rocker to spec to simulate the way the engine will be running. When an engine is running it is pumping oil into the lifter and thru the pushrod. When its not running, there is no oil pumping so when you turn the engine over by hand,and the cam starts to push the lifter up, Instead of the pushrod pushing the rocker which pushes the valve all the way open to its max, The lifter bleeds off oil and compresses. (gets shorter on the inside) When this happens Your valve is not opening all the way like it would when the engine is running and the lifter is pressurized with oil. So if you take your measurement with a solid lifter it is duplicating a pressurized lifter.

When you have a solid lifter, or a modified hydraulic, drop it in place. Then take some modeling clay, (from HoBBY LOBBY or such) Make a pancake of clay, not too thick, and put it on top of your piston, Right in the center where your valves will come. You put your heads on with gaskets, and then tighten the bolts. dont torque them, just snug them so they cant move. Put your pushrods in, then rockers , (Make sure the lifter is on the base circle of the cam) torque your rockers, down. Then rotate your engine 1 full revolution. then take the heads off, and using a set of calipers,open them up, push the end of the calipers into the clay until it hits the piston top, then carefully and accurately slide the calipers down until they touch the top part of the impression the valve left. Look at teh measurement, that tells you how much piston to valve clearance you have.
A tip is to put a fine film of oil on the piston top to help get the clay off.... hope this helps