Valve Seat Concentricity Shocker

[cgarb]

I cut valve OD's on my lathe too. Cheap 5c collet chuck and Chinese collets. I can get stem run-out less than .001 (with considerable rework on my part) I have never checked the faces with a tool like that sunnen. I would imagine a similar set up could be made with a v block and some fixturing. The best way I found to turn valves was with the grooved end in the collet and the stem in a steady rest right before the undercut. That gave me the most accurate run-out with less chatter. I finished my valve faces on a kwick way grinding machine.

[WeingartnerRacing]

I have old Sioux with the accu chuck. The machine is amazing. I don’t think they make a new machine that is better. My worse case has been .0005. I attribute that more to the stem being not straight from factory. However you have to have more than .004 before leakage shows up.

I don’t use that guage you use David. An easy test is reface the valve then loosen the collet and turn the valve. Then tighten the collet back up then start grinding. If it doesn’t clean up right away it’s out of round.

[vortecpro]

"A valve is ground and checked – 2 thousandths out!! Worse than the ones I feel are a problem. I go to another shop – 3 thou out then another 1.5 out"


Maybe you should ck their seat work next time..........LOL

[vortecpro]

I have old Sioux with the accu chuck. The machine is amazing. I don’t think they make a new machine that is better. My worse case has been .0005. I attribute that more to the stem being not straight from factory. However you have to have more than .004 before leakage shows up.

I don’t use that guage you use David. An easy test is reface the valve then loosen the collet and turn the valve. Then tighten the collet back up then start grinding. If it doesn’t clean up right away it’s out of round.

I'd be buying a valve run out fixture If I was you. Mine are K Line.

[modok]

My employer had the policy of facing -every- valve even if they are new. I thought that was a waste......but

Now I check the valve runout on EVERY head I have apart, even if they look perfect. (learned the hard way)

.002 runout will work FINE, of course aim for perfection but don't get your head too far up in ......the clouds
Install a head with a tweaked valve, even once,.....you will agree with me.

[MadBill]

My employer had the policy of facing -every- valve even if they are new. I thought that was a waste......but..

How about with completely coated Ti valves; just check them?

[superpursuit]

I have a centre less valve grinder that consistently gives me less than 2 tenths run out. There is no chuck or rotating collet to give run out. It has a pair of opposing V blocks that support the valve and a drive at the rear of the valve spins it. This particular machine comes with it's own off the machine concentricity checker, that has a Mitsutoyo Tenths dial indicator on it, as standard equipment. Those of you who are checking the concentricity in the chuck are not checking valve concentricity at all. You are checking the concentricity of the valve and chuck assembly only. Or to put it more simply you are checking how free cutting your grind stone is. If you don't isolate valve run out from chuck run out then you don't know the run out of the valve itself. All the chucks I have seen have run out. A proper concentricity gauge is an eye opener. I have found that on small multivalve heads with tight tolerance valve guides even just .0005" run out on valves will affect their sealing. I believe that accurate valve & seat tolerances, and all engine tolerance as well, are very important. I always check the run out on every valve, especially new valves. Not too many pass this test.

[modok]

My employer had the policy of facing -every- valve even if they are new. I thought that was a waste......but..

How about with completely coated Ti valves; just check them?

I don't think they had titanium valves when he learned the trade, and if they did they certainly were not coated.

[mag2555]

Can we heat a head to the general temp and local temps they accually run at and do a vacuum test to may be get a clearer picture of how much accuracy is really needed?

I hate to venture a guess of how much a .0005" run out condition at room temp changes for instance on a running motor where the Intake seat / valve bowl leans / Butts up against the Exh seat and valve bowl?

I am of the thinking that besides the accepted amount of guide minimum clearance we have , that we may also need more to allow the valve to shift and accommodate the head as it shifts and still allow the valve in question to seat well!

Does anyone who has a motor that has been run and still shows a from a leak down test only 3% that they / we need to fight for more?

I myself would love to know how much the chambers in a Aluminum head bounce around in a running motor @ 6000 rpm or better when you have over 600 psi of spring pressure trying to tare the head in two at its horizontal plane, what effect does this have on valve sealing folks?

[DaveMcLain]

Can we heat a head to the general temp and local temps they accually run at and do a vacuum test to may be get a clearer picture of how much accuracy is really needed?

I hate to venture a guess of how much a .0005" run out condition at room temp changes for instance on a running motor where the Intake seat / valve bowl leans / Butts up against the Exh seat and valve bowl?

I am of the thinking that besides the accepted amount of guide minimum clearance we have , that we may also need more to allow the valve to shift and accommodate the head as it shifts and still allow the valve in question to seat well!

Does anyone who has a motor that has been run and still shows a from a leak down test only 3% that they / we need to fight for more?

I myself would love to know how much the chambers in a Aluminum head bounce around in a running motor @ 6000 rpm or better when you have over 600 psi of spring pressure trying to tare the head in two at its horizontal plane, what effect does this have on valve sealing folks?

Not to mention how much the head flexes out of shape when it is torqued down to the top of the block.

[peejay]

And combustion pressure pushing the chamber up...

Looking for a pic of a pinned/posted Cleveland head.

[Frankshaft]

What about using a magnetic base indicator holder, and indicate the stem, to make sure its in straight, or is straight, then grind the valve, and put the indicator on the valve face. It will show you the run out, without removing the vale from the grinder. Thoughts? That's how I do it. As stated above also, vacc checking seats, has to be done on the machine. LIGHTLY set the valve on the seat. The only thing influencing the seal, should be the weight of the valve sitting on the seat. If it pulls FULL vaccum, its good. If its in the "green" but doesn't max the gauge, its leaking, period. I have seen numerous youtube videos of people cutting seats, and they always "SMACK" the valve on the seat, then vacc check it. NO, that's not a true test. Same with assembling heads, then vacc checking. Well duh, of course it will seal with a spring pulling the vale into the seat. I have also seen guys do that too. Whats that show?

[David Vizard]

After checking the run-out on my collet chuck (almost zero) I looked arround for other issues. Looks like a damaged thread from a drop. As the collet reaches the final tightening it's off axis push from the thread was enough to move the back of the collet over a tenth or so which then amounted to 3 tenths at the front of the collet and about 9 tenths at the valve face. So the problem is solved.

However my point was that three shops I went to for a seat job produced errors greater then I was already seeing. And for those folk who expected a spot on job - - well would they know otherwise.


All I can say here is that a check lap with 800 or 1200 grit paste could go a good way toward detecting excessive eccentricity.

DV

[GARY C]

Can we heat a head to the general temp and local temps they accually run at and do a vacuum test to may be get a clearer picture of how much accuracy is really needed?

I hate to venture a guess of how much a .0005" run out condition at room temp changes for instance on a running motor where the Intake seat / valve bowl leans / Butts up against the Exh seat and valve bowl?

I am of the thinking that besides the accepted amount of guide minimum clearance we have , that we may also need more to allow the valve to shift and accommodate the head as it shifts and still allow the valve in question to seat well!

Does anyone who has a motor that has been run and still shows a from a leak down test only 3% that they / we need to fight for more?

I myself would love to know how much the chambers in a Aluminum head bounce around in a running motor @ 6000 rpm or better when you have over 600 psi of spring pressure trying to tare the head in two at its horizontal plane, what effect does this have on valve sealing folks?

Not to mention the casting is around 200+ degrees and tq-ed down but the chamber, chamber side of the seat and valve see a much higher temp and much greater temp variance over and over in cycles.

[NORSK]

I wonder how concentric a exhaust valve is after it has seen a few minutes of 1000 deg celsius egt
And being hammered against the seat and forced open something like 60-70 times pr second
Not so much i guess
So it might not be that critical anyway