Valve to piston clearance
 

What is the best way to check your valve to piston clearance during a rebuild of a 3.2 to a 3.4 engine? And what should I end up with for clearance, I am using Bored to 98mm cylinders, J&E 10:5.1 Pistons, Super cup profile cam from J Dougherty

Thanks

A little off topic, but I have the same PC set on my shelf to a 3.4. What are you using for injection? Standard 3.2 manifold? Are you going Twin plug, and if so, what are you using for that?


Thanks.

Using the stock injection, andial splitter with a 964 dist, twin plug heads and have Steve burn me a chip for the Motronic

Read Wayne's book on how to do both piston to valve and head clearance.
Use solder to measure head clearance and you do the valve to head after you have everything timed. You then rotate the crankshaft to various positions and turn the adjusting screw until your valve hits the piston or you exceed at least two turns. You map the clearance from around 240 to 440 degrees for intake and exhaust.

Search for info on head clearance and piston to valve clearance. There may be diagrams.

I know it had to be reassembled to check the clearance. On my 912 engine I checked it with clay, but a push rod engine is a lot easier to pull the heads to check. Using the valve adjuster looks to be a great way to do it, if it checks out ok then there is no need to disassemble it.. I will check it out in his book

Thanks

I have always checked the piston to valve clearance by adjusting the valves so that I had 0.100 inches of preload. If you can rotate the engine without the valve hitting than you can be sure you have clearance. If it does hit you can back off the valve adjustment to come up with the actual number you need to machine off of the pockets.

Good luck,
neil

You may want to check with Camgrinder on what he recommends for clearance, Web-Cam states a minimum of .050" on the intake and .080" on the exhaust is needed.

.050" on the intake and .080" on the exhaust is the minimum needed. Waynes method works fine.

I think you'll be fine. 98mm 10.5:1's JE's with 964 cams have a huge amount of valve clearance. I think that last one I measured have something like 5mm of clearance. I think the valve pockets are pretty deep. I suspect that your supercup cams don't have as much lift as those pistons were designed to handle.
-Chris

Craig

I find Waynes Method a bit tedious, what I do is assemble a head with just the inner spring on each valve, put the dial gauge on then as you turn over the engine depress the rocker with a screwdriver and read the clearnce off the dial gauge, it saves all the turn back and readjust fiddling

HTH
Neven

Neven, you check it 15 degrees before and after as well as at top dead center?

John

With this method its really quick to map the whole clearance profile (within reason) I measure every 10 degrees or so and then go back to find the min clearance

Cheers

Great idea Neven!
-Chris

Not that hard with the screw method - and the JE's have big valve pockets so usually not an issue either way.

Chris, reading your comments on Craigs clearance with 10.5-1 and 964's is it really worth me doing this check on my 930 with 3.2 carrea heads, 97mm je's at just under 8-1 comp and 964 cams?

Yes, do the check. It's worth it. I'm not into wasting "life force" (sounds so much better than saying I'm lazy doesn't it?) but I check everything I can.

Aside from the diameter, your low compression JE pistons are nothing like mine or Craig's. Even JE's changed their design since the first set I bought a few years ago.

When it comes to building these motors my motto is:
Trust No One, Measure Everything Yourself.
-Chris

That's probably the best piece of advice in this whole forum.

cool. ill measure. Ive read in other posts that you only need to do one side? sort of makes sense as if you have like 5-6mm of clearance on the first side then its almost impossible for the other to be under 1.5 right?

Always do both sides, or Murphy and his family will catch up with you. It's the law.

Great method with the dial gauge NevenM, I'll keep that in mind for the next time!

George

George is right. That Murphy guy is always showing up at the least convenient times.
Me: "I'm sorry Mr Murphy I was just heading out, another time perhaps?"
Murphy: "That's OK, I'd rather do my thing without you watching anyway. It'll give you something to think about while you're in bed trying to sleep."
-Chris