Set valve clearance on bench?

[Jhurt]

I?m at a stopping point where i need to order some parts and wait for them to arrive. I?m looking at the design of the motor (1978 GS750) and thinking it should be possible to check/set the valve clearance with the head on my bench. Since the cam lobes are the only thing interacting with the valve buckets i would just bolt the cams in place temporarily and go about measuring so i can order the shims with the other parts i need at the same time.

Am I missing something here? Would the clearance change after torquing the head down during reassembly?

 

[Nessism]

Checking on the bench seems like a good idea but I'd double check once the engine is assembled.

 

[Burque73]

You may already have an idea how to rotate the cams without using the crank and cam chain to do it, but if not you can use a strap wrench.

https://www.harborfreight.com/rubber-strap-wrench-set-2-pc-69373.html

 

[fbody_mike]

I know V8 engine block can distort a bit when the heads are bolted on vs. not bolted on, which is why they use torque plates when boring the cylinders so I guess it is possible the heads would distort a little too. I'd guess not enough to cause any difference in a feeler gauge. Make it a little experiment. Set the clearances on the bench, record the clearances, then after it is bolted down, check again and report back to us if it changed.

Only other thing I'd worry about would be to support the head securely on the bench with space for the valves to move and also to not let it slip and crash down on a depressed valve.

 

[Steve]

My biggest concern would be holding the cams in the correct positions. Of course, this assumes that you know what the correct positions are, but that's a topic for another thread.

.

 

[GregT]

Of course you can do it on the bench. A couple of blocks of wood - one at each end - gives clearance for the valves to lift.
Or you can make up stands.
Turning the cams - even with race springs in - isn't that difficult. I use a 10mm ring spanner on the cam sprocket bolts.
Use a torque wrench on the cam cap bolts and lube everything well.

There's no reason whatsoever why the clearances should change once the head's torqued down.

Edit - On a freshly assembled head, I turn each cam over 2 3 times before measuring clearances to settle everything down.

 

[fastbysuzuki]

Just make sure you do not rotate the cams without a shim in the buckets.

 

[Jhurt]

Alright that?s what i was thinking, just wanted to make sure there wasn?t something i had missed. Thanks all.

 

[bwringer]

Yep, block the head up a bit and secure it so it CANNOT fall off with a cam installed and a valve extended.

And oil everything.

And yeah, make sure you don't rotate the cams without shims.

I would double-check once the head is installed, but there's no reason the clearances would change.