piston to valve clearance

[Rev]

The best and most accurate way to get piston/valve clearance is to install very light springs on the #1 cylinder valves. Mount the head using the old compressed gasket torqued to 25 lb/ft or so. Put the #1 piston at TDC at the end of the exhaust stroke/ beginning of the intake stroke. Put a dial indicater on top of the spring retainer and push the valve down with your finger until it hits the piston. Do this a few degrees before and after top dead center. As mentioned earlier, use a solid lifter for this measurment set with 0 lash. Record how much further you can depress the valve after it's opened by the cam. That's the piston valve clearance. Do the same thing for the exhaust valve.

I had the machine shop install the weak testing springs which I borrowed from them. I went home and did the test and then came back to them for reinstallation of the real springs. As Gearhead said, you will want .100" clearance. My machine shop guru insisted that I do it that way instead of the modeling clay technique. He said "yeah, it's great if you have a whole lot of extra clearance, but what if it's close? How accurately can you mic that piece of modeling clay?"

Rev

[~The Jester~]

Originally Posted by Rev

The best and most accurate way to get piston/valve clearance is to install very light springs on the #1 cylinder valves. Mount the head using the old compressed gasket torqued to 25 lb/ft or so. Put the #1 piston at TDC at the end of the exhaust stroke/ beginning of the intake stroke. Put a dial indicater on top of the spring retainer and push the valve down with your finger until it hits the piston. Do this a few degrees before and after top dead center. As mentioned earlier, use a solid lifter for this measurment set with 0 lash. Record how much further you can depress the valve after it's opened by the cam. That's the piston valve clearance. Do the same thing for the exhaust valve.

I had the machine shop install the weak testing springs which I borrowed from them. I went home and did the test and then came back to them for reinstallation of the real springs. As Gearhead said, you will want .100" clearance. My machine shop guru insisted that I do it that way instead of the modeling clay technique. He said "yeah, it's great if you have a whole lot of extra clearance, but what if it's close? How accurately can you mic that piece of modeling clay?"

Rev

Yep, what he said!!! I run it the same way, cept I check it with the dial indicator for one FULL revolution. I'm anal about that kinda shyt. Problem with "clay" is how much does it distort when you peel it off of the piston? How much does it distort when you clamp it in your calipers?

We're literally playing a game of .001" and "playdough" is just not accurate enough in my book. Heck, anything that has "play" in it's name has no business near my engines.

I keep a set of used head gaskets on hand for this exact reason!!! Just remember, you play like you practice, so make sure you're using -1 gaskets to check clearance on an engine that's actually going to use -1 gaskets. Checking with -1's and running -2's ain't gonna be accurate!