When installing a new head on a re built engine you have to check for piston and vaalve clearance, On a street engine .040/,050" over both is what I shoot for. Most of the new Edelbrock heads have quite abit of valve clearance so that's not a problem. The older heads and especially Offys do not clear the Hi Lift cams like the 400jr and L-100. It;s best to check piston clearance befor the valve are installed.
I put little aluminum balls on the pistons one in the center and one on the edge. Install a used head gasket amd clamp down the head with a few bolts, rotate engine and remoe head and measure the thickness of the balls. This will be your running clearance. Most heads have.o6o/,080" clearance. this tells you how much to mill the head t get your desired clearance. on the 294 with Ross pistons we milled the new 74cc Edelbrock heads .025" resulting in .045" clearance. This was checked by snaking in a piece of solder into the spark plug hole after the heads were torqued to 45 ft/lbs and came out at .050" I hpped for a tighter chamber but this will work just fine.
If you have a piston hiting the head, ypu'll have to have it re-domed for proper clearance. on the early heads I have the valve clearance by tipping the head to a 5 degree angle and using a shell mill cout the valve clearance. After all this is done you cc the head to find the CR, if it's to hi you can extend the transfer area to lower it. Not much you can do to raise it. You have to plan these things when starting the build. After spending several thousands of dollars on th short block, installing a properly prepared cylinder head will take advantage of all the rest of the parts. Now adding carburation and ignition systems with the same fore thought and you have one hell of an engine. Power and economy in one package.
