Machinist Guys! Thoughts on installed valve stem height

[EchoWars]

Have an old 225 Buick Odd-Fire V6 that I have apart, and had the valves ground and hardened seats installed on the exhaust. Once I got ready to put the heads back on, I noticed that there was some real variances on valve height. Laying a straight edge on the tops of the valve stems shows that the lengths are all over the place. I measure a difference of .034" from the longest to the shortest valve stem. This is going to be a real issue with a non-adjustable valve train.

Know that I'm fully aware that I don't own the proper gauge to accurately measure installed valve height, BUT the spring seat on the head is just enough bigger in diameter than the retainer that I can get the tail of a caliper on it and measure to the top of a straight edge (then subtract the thickness of the straight edge for a measurement). Yes, it's crude, but it is repeatable. Went through the measurements several times.

So, I'm trying to figure out a couple of things:
1. How much variance is acceptable? Did a lot of valve jobs back in the early 80's and I could swear that the machine shops were holding height variances to +/-.005" (.010" max from longest to shortest stem). Is that unreasonable to ask of a shop to do?

2. AERA book says stem height from 1.930" to 1.970". I assume that the first number is the minimum acceptable height above seat, and that the 0.040" difference between the two numbers is simply what allows for proper valve train geometry, and not the acceptable variance for a given engine. IOW, find a number in that range that all the valves will be happy with, and make the necessary adjustments so that all are within a given tolerance (such as my suggested +/-.005"). Am I interpreting that correctly?

Just trying to figure out what to say to the machinist, if anything. Don't want to come off like a lunatic...just trying to educate myself before I go any further. Thanks!

[mag2555]

Many things come into play in regards to the overall valve stem height .
1) how much the valve seats where cut to clean them up.
2) how much the valves where cut to get a wide enough seating area back on them if they are used valves.
3) the other side of number 2.
Any new valves will likley have a closer to stock shorter overall all stem height.
4) how much the stems on used valves where cut to true them up.
5) if seats where installed on valves where getting a fresh working seat would have sunk the valve too far.
Another side effect that happens when a valve gets sunk down into the chamber is a big change in flow can take place, and all to many times it's not a change for the better and can make it hard or impossible to get that cylinder to tune/ run like the others !!

[EchoWars]

I understand the variables involved, but ultimately it comes down to two major measurements: height of valve stem above spring seat, and installed spring height. Not really asking how to correct (there's several ways to do so), I'm more asking what I ought to expect from the machine shop (to whom I paid a pretty penny for the work). What's acceptable, and what blows.

[Keith Morganstein]

Should be easily able to get +\- .015" on all valve jobs. Might be an exception for a "salvage" job on an engine with adjustable valve train.

Now you have to decide if it's worth sinking the valves to equal them out or go to different pushrods lenths. Pushrods come in .050" increments. A hydraulic lifter will compensate for less than that, but you need some preload on all of them.

[houser45]

It all depends on what you paid for if you paid for a valve job consisting of just grinding your valves touching your seats with the stone and back together that’s probably all you’re going to get, if you paid for a better race engine style valve job where the valves themselves were +\- .005” in the chamber and the Stems within .015” on the top. The other thing is the tolerance on where the lock grove on the valve is compared to the tip and the tip to the valve seat surface is a fairly wide tolerance when the valves are even new.

[PRH]

I would say if the tip heights all fall within the 1.93-1.97 AERA spec, and you paid for an oe type head reconditioning....... and that’s the way the heads will be used...... you’re good to go.

[machinedave]

If the seats were installed properly and the valve job was cut properly (verify with layout dye or black marker on the valve) then it's likely that the intakes are sunk a little. Machinists always try to get the heights as close as possible but I have seen some machinists(wrongly in my opinion) sink some perfectly good seats just so they all match. You could try switching the valves around to try and equalize heights. If the lifters have enough plunger travel after all of the machining it should run.

[Schurkey]

When I asked about the same question (in regards to a Vortec-style aftermarket replacement head) I got all sorts of answers.

https://www.speed-talk.com/forum/viewtopic.php?f=1&t=52505

If I had it to do again, I'd have kept the heads and dealt with the valve tip unevenness.

[PRH]

When I asked about the same question (in regards to a Vortec-style aftermarket replacement head) I got all sorts of answers.

https://www.speed-talk.com/forum/viewtopic.php?f=1&t=52505

If I had it to do again, I'd have kept the heads and dealt with the valve tip unevenness.

FWIW, with regards to your situation with the EQ heads....... I’m in 100% agreement with Frankshafts response in that thread.

[Dave Koehler]

If the seats were installed properly and the valve job was cut properly (verify with layout dye or black marker on the valve) then it's likely that the intakes are sunk a little. Machinists always try to get the heights as close as possible but I have seen some machinists(wrongly in my opinion) sink some perfectly good seats just so they all match. You could try switching the valves around to try and equalize heights. If the lifters have enough plunger travel after all of the machining it should run.

OR
it could be that the intakes are within reasonable specs and the new exhaust seats were not machined down to factory height.

We learned to take readings on heads that had no written spec during tear down. Then refer to them during machining to stay close to that original reading. Never an issue that way. After a while we would have some averages logged for a particular head to refer to.

The only thing that can be done in this case to find a baseline is to check some untouched heads for stem height.
I wonder if it might be listed in the Prosis software.

[Newold1]

What is the current highest stem height you measure? If it's at or less than the 1.970" height then the other seats and valves should be able to be machined slightly to bring them up to that 1.965" to 1.970" or less with +- .005".
As has been mentioned here if the face to top of stem heights vary enough that you can move the valves around that will make correction possibly easier if they all balance a little closer in installed heights. If this machining is required I think it should be the responsibility of that shop to make the corrections.
The engine is a hydraulic lifter engine so I am pretty sure the lifter plunger travel can handle probably about .020" to .025" of increased depth without any issues in a stock engine application. JMO

[modok]

If it's in-spec, then it should work fine.
If you wanted something different should have said so.

I KNOW a lot of machinists cut the valve tips equal on all heads but I don't agree this is a good idea.

That's a long story in itself why you would or would not want to do that, but, these days, valves have hard tips that are only a limited thickness, and why shorten all your valves to match your worn seats?
Then what happens of you fix the seats? then your valves are too short. SO, it is possible the current problem was CAUSED by the LAST GUY grinding the tips even.
DID YOU GET NEW VALVES?

[EchoWars]

If it's in-spec, then it should work fine.

I'm not at all sure that they are. I suspect that several valves are under the minimum installed height spec.

If you wanted something different should have said so.

While I'm not totally ignorant of valve train geometry, I kinda simply trusted these guys to get it done no-muss no-fuss. They are the pros, and this was NOT a cheap adventure.

DID YOU GET NEW VALVES?

Nope...all the same valves. Shop said they were in good shape.

[houser45]

This is how I do a valve job for how I feel is the correct way, start off and either do all the intake or all the exhaust valve seats find the shortest height valve out of all of the eight intakes by dropping all eight valves in the same chamber and find the shortest one in relation to the Deck, use that valve to cut all eight seats Within .003” , then go back through all your valves and grind the ones that are tall to match up so you can try to get all the Heights the same. If they are new quality valves the tip heights should be relatively close it is more important to have the valve Heights in relation to the deck as close possible then having all the tip Heights exactly the same .

[af2]

Why the heck wouldn't the heights be the same if a competent builder did the the job?