Valve-Piston Clearance Check!

cab83_750 · 09-23-2006, 08:42 AM

I have Wayne's book and the check is mandatory for my case; I have regrind cams, 9.5 JE, heads done by Walt, and the engine is an early SC engine.

The check requires that I assemble the car without the seals...then disassemble it. So, what are the chances of my clearance being out of specs?

I have been thinking about actually sealing everything, then checking in the hope of the clearance being OK.

For those of you who rebuilt their engines, what did you do?

Thanks.

shbop · 09-23-2006, 09:57 AM

I hope someone with more experience will chime-in, but if I were you, I'd want to be sure. The cost of an error at this stage is significant. Both emotionally and financially.

Eagledriver · 09-23-2006, 06:36 PM

I understand not wanting to waste the effort on a dry assembly. What you can do to cut some corners is to only use a few nuts on the cam towers instead of all of them. You also don't have to fully torque the cam nuts/bolts. or tighten the rocker shafts. You could even just do one side initially and if it's not close on that side assume the other side will be ok and check it after final assembly. In effect all you have to do is:

Install heads, put cam tower on with 6 nuts or so, install intake rocker on number 1 or number 4, install chain housings (these can be left on so they are final), install cam (do this before the rocker of course), put sproket and chains on, time the cam. You don't have to do the shimming of the sprocket until final assembly.

The only thing you have to do to go to final assembly is remove the rocker, cam, cam tower and heads. This is very quick and easy.

If you do these shortcuts it will only take an extra hour or so and you get a free practice for the final assembly.

-Andy

racing97 · 09-25-2006, 02:21 PM

If you know your valve lift at TDC for both the inlet and exhaust and you have one piston and cylinder and one head with the springs off push the piston up to the top of the barrel wilth zero deck than push is down the 1mm for your deck height. Install the head upon the barrel with and with a vernier caliper pull the valve all the way to the seat measure then let it drop and measure the difference. Knowing that the intake valve is closest 5 to 10 degrees ATDC and the exhaust is closest 5 to 10 BTDC you will be looking for ample clearance because you are not dulplicating the exact position I would say 3mm or so would be safe in such a cercumstance.
It sounds funky but it is good for getting a rough idea.

regards