I know of the method with the modeling clay, but I don't have any spare headgaskets with the width of the compressed Cometic. There has to be another way that doesn't require me to waste a headgasket in the process. I've heard there are a couple other ways to do this, but I can't seem to find them on Google. Anyone have any suggestions? This is pretty much the only thing holding up my build right now but I'm not going to just slap it together and hope for the best, not with the amount of money I have invested thus far. Any help from the gurus?

I'm looking for something that uses more mathmatics than physical measurement. ;)

Why would the clay method ruine the head gasket? The book I have on blueprinting recomends that method. I'm a newb, just asking.

What about using the clay method without a head gasket? I would think that if something hits, chances are you're still too close (given thermal expansion, gasket compression, rod stretch, etc).

^^^ what he said. I've used the clay method on plenty of chevy engines and plan on doing the same when I begin to throw my engine together. or just use an old one if you have one laying around

I guess I could go that route with no gasket. I just figured that by compressing the gasket by torquing the heads to the block, you are pretty much ruining the headgasket. Can it be reused after being torqued?

You want around 0.100 of clear, that's a lot more than the 0.6 mm head gasket. Don't use a head gasket and don't torque it all the way down.

If you have AVCS, things get much more complicated.

The instructions are for a domestic V8, but the article explains the process. It is the best way (IMO) to determine valve clearance.

http://www.cranecams.com/pdf/20e.pdf

Plus as long as you don't use a sealer on the head gaskets and don't start the engine, you can reuse head gaskets. The heat cycling of the engine is what brings out the "glue" in composite head gaskets causing them to sick to the adjoining surfaces.

Do not check piston to valve clearance with out a head gasket. You will get a false reading because the cam timing will be wrong.
The easiest thing to do is take a large screwdriver or small pry bar and mod it so you can use it to depress the tappets when the head is assembled. Once you have the shape right on your tool polish it up real good so it wont mar the tappet or cam.
The exhaust valves will be closest to the piston between 8 and 15 deg before TDC on the overlap. I always check every two degrees 8, 10, 12, 14 till I find the least clearance. So you will turn the motor to 14 deg BTDC and zero an indicator on the tappet then use your pry tool to push the valve the rest of the way to the piston. This measurement will be your piston to valve clearance. Repeat this step every two degrees till you find the smallest clearance.
The intake side is the same except that it will be the closest 8-15 deg ATDC.
If you are too close then usually going one degree larger on the lobe center number will get you .004" more P-V clearance.

The trick with our motors is the DOHC. You have to adjust for variance between the crankshaft and the camshafts. Too much advance on the intake camshaft or too much retard on the exhaust cam spells trouble.

Without AVCS you can slip the timing belt a tooth or two to simulate advance or retard and then rotate the engine with clay.

You can dispense with the clay, but you are looking at a lot of dial indicators set up and recording. You'll have to record location of the piston as it reaches TDC, lets say every two degrees for 60 degrees before and after TDC (install a degree wheel). You'll have to work backwards, start straight up on the crank, turn the crank until dial indicator indicates TDC, rotate back 60 degrees.

Now move the degree wheel to the camshaft and turn it to the position that corresponds to 60 degrees before TDC (camshaft degrees are 1/2 crankshaft degrees) you'll have to start from straight up on the camshaft (timing marks are at 9 and noon ti believe). Now you'll have to measure the depression of the valve as you rotate the camshaft 30 degrees to TDC and then 30 degrees after. This will be the tricky part. Where do you put the dial indicator on the valve to measure it. It's sitting in the head at an angle. The piston valve reliefs are at an angle (hopefully the same angle). I'd probably put the indicator in the middle of the valve and then measure the tip separately and assume that the valve is moving straight.

The whole pent roof design makes this a very difficult measurement, slipping at tooth or two,and using clay or even resistance (valve contact with piston) is a whole lot easier.

Maybe I'm not reading this right, but couldn't I just assemble the longblock with some clay on one of the pistons and rotate it through two cycles and get what I need? The headgaskets are .051" Cometics. I don't think I'm going to make contact here, the valves are standard sized and the cams were made for an EJ205. I think the dish on my pistons is actually a little deeper than stock. But I'm not certain, I could measure the crown to dish surface distance and if is is the same or deeper than the WRX piston then wouldn't I have enough clearance...especially since I'm using a thicker HG than what is used on the WRX? I'm just throwing out ideas here.

Went ahead and did it using the modeling clay technique, no issues whatsoever. Only torqued the heads down to 10ft/lbs, but I don't think that will make much of a difference on the thickness of the headgasket. Everything checked out.

I wish I had read this earlier but maybe you can try this after final assembly. An easy way to check valve to piston clearance is with a piece of solder. You can get it in different thicknesses and it can be bent to fit into the sparkplug hole. When the motor is assembled you hold a long piece in the plug hole and get it to compress while you carefully turn over the motor. You may never actually compress the solder if you get a gauge slightly thicker than your allowable gap. If you must know the exact gap than you should use thicker stuff then measure the compressed part.
This tip is very useful when installing high lift cams. You won't have to pull the heads to check the gap and because this is so easy you'll be more likely to do it. Now you won't have to wonder if bad things are going to happen if you accidentally over-rev your engine.

You should've called the piston manufacturer. They could've told you that. The pockets at the top of the piston dishes are usually pretty generous. I suppose if you had really high lift then it might be a problem. With that .051 gasket, you could be leaving power on the table actually. That's part of checking deck clearance.

i'm in the same boat of asking this question so hope you dont mind me jumpin in while it's being discussed. i have an ej257 with cp 8.2:1's and wrx heads. i am using ferrera valves (stock sized), sti head gaskets, and 272's so am i going to run into a clearance problem or do you think i should be fine with the big dish? my heads just came back from florida and the "installer" of the valves did a great job so i'm kinda thinkin i should be fine on clearance. let me know! THANKS! -:devil: p.s. thanks for lettin me jump in.

If you can pull your heads apart, then you can check them this way.

Install lighter springs on one cylinder, intake and exhaust. Assemble engine, install degree wheel and dial indicator, bring engine up to desired amount. Push on lifter and watch dial indicator. This will show the clearance.

I wish I had read this earlier but maybe you can try this after final assembly. An easy way to check valve to piston clearance is with a piece of solder. You can get it in different thicknesses and it can be bent to fit into the sparkplug hole. When the motor is assembled you hold a long piece in the plug hole and get it to compress while you carefully turn over the motor. You may never actually compress the solder if you get a gauge slightly thicker than your allowable gap. If you must know the exact gap than you should use thicker stuff then measure the compressed part.
This tip is very useful when installing high lift cams. You won't have to pull the heads to check the gap and because this is so easy you'll be more likely to do it. Now you won't have to wonder if bad things are going to happen if you accidentally over-rev your engine.

With a cold engine, the piston will have more clearance to rock back and forth. Just something to keep in mind.