Safe Way to Check Valve-Head Clearance?

[Shoebox]

I have assembled a 276 flathead with an Isky 1007B cam which has .365 lift that Pete ground for me. Some have said that my new Offy 400 heads may not offer enough valve clearance. I know the mantra of measure, measure, measure. I have done the clay/foil balls thing to measure piston to head clearance before, but I'm dreading the prospect of bending valves checking this out. Is there an alternative to bolting on a head w/gasket, rotating to see if something hits? As assembled the engine is tight, don't think I can slowly sneak up on an opening valve. Couldn't one measure the height of an open valve and compare to depth of valve pocket in head? I welcome all comments and suggestion.........Thanks guys.

[38 coupe]

The easiest way to check is to set the head on without a head gasket using a couple long bolts that won't hold it down, and slowly rotate the crank to see if the head is lifted. Be careful not to put pressure on a valve. If no contact without a head gasket then you're good to go.

[Shoebox]

Thanks 38coupe, I was thinking the same. The part about "careful not to put pressure on the valve" is what still concerns me.

[Ol' Ron]

Using apiece of rosin core solder placed ofer the valve head rotate the engine with the heads on the block, but not bolted on. Excellent cam choice!
Gramps

[cadillac512]

Originally Posted by Shoebox

Thanks 38coupe, I was thinking the same. The part about "careful not to put pressure on the valve" is what still concerns me.

With just the weight of the head, no damage will be done to the valves even if they lift the head on the loose bolts when they open. You needn't worry about that at all.



Terry

[Shoebox]

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Ron & Cadillac,
Thanks for the comments, feeling a little less apprehensive about this. Next dumb question,...should I have the head gasket under this loosely bolted head when doing this? Thanks.

[Zeke3]

Originally Posted by Shoebox

should I have the head gasket under this loosely bolted head when doing this? Thanks.

Yes, no gasket, that is your safety margin when you finally install the head.

[cadillac512]

Exactly. No gasket during the testing. If it clears with no gasket you can be sure there's plenty when gasket is installed.



Terry

[Shoebox]

OK guys,
I will proceed as described, thanks.

[Ronnieroadster]

I do it a bit different first I use duck seal - putty its easy to place on the valves and also across many locations along the top of pistons. Next I use the head gasket. After rotating the engine a number of times I can not simply use a vernier caliper to measure the compressed height of the duck seal - putty. Clearance is now known.
Ronnirroadster

[Bored&Stroked]

I do it exactly like Ronnie does - as I'm as concerned about piston to head clearance as I am about valve clearance.

Truthfully, valve clearance is a lot easier to accomplish (at home), than issues with piston to head clearance. Flatheads like about .040 to .045 over the pistons . . . if you have more than that, you're hurting performance. So, I deal with both at the same time . . . with kids modeling clay.

[Ziggster]

I have the same cam from Pete but will be using my stock iron heads on my C59A. I want to do the same just for my self assurance. Likely is ok, but just want to see what it is. Got some plasticine and will be checking this in the next week or two as it is the last thing before buttoning it up and getting it ready to run.

[Shoebox]

Originally Posted by Ziggster

I have the same cam from Pete but will be using my stock iron heads on my C59A. I want to do the same just for my self assurance. Likely is ok, but just want to see what it is. Got some plasticine and will be checking this in the next week or two as it is the last thing before buttoning it up and getting it ready to run.

Ziggster,
Perhaps you could report your findings after checking? I have switched to the removal of my original 6 cyl. driveline and cleaning/painting of the engine bay at the moment. Thanks.

[Ziggster]

Most definitely.

[Ziggster]

Here are the results. Some pics of getting TDC with cyl #1.

[Ziggster]

Pics of setup.

[Ziggster]

Piston to head clearance - 0.073 to 0.076”. Felpro Gasket in place - 0.055” thk. Headbolts torqued to 25 ft-lbs in sequence.

[Ziggster]

Intake valve. There is an angle to the modeling clay. Clearance is about 0.060” at the top of the valve and about 0.160” at the bottom.

[Ziggster]

Exhaust valve. There is an angle to the modeling clay. Clearance is about 0.121” at the top and about 0.223” at the bottom.

[Ziggster]

Also checked sparkplug electrode clearance with exhaust valve. It was about 0.128”, but electrode is on an angle with the surface of the valve. I’m using NGK B-6L sparkplugs.