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Old 02-22-2006, 06:31 PM
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Valve Stem Height

More dumb questions regarding my L-98 Aluminum Heads....
I had my shop do the 'standard' 3 angle valve job but was told that they couldn't grind the exhaust valves properly because the seats were worn and 'sunken'. The most cost effective solution offered was to replace the stock 1.50 valves with new 1.60 valves and grind the seats accordingly to accommodate.
They did a great job of machining everything but I noticed several things that concern me:
1- The new exhaust valves are about 1/8" shorter from head to tip than the old valves and the existing intakes. Should I be concerned?
2- Since the new valve is somewhat shorter, the stem doesn't line up in the head with the intake valves (which looks odd to me). Is this a problem and will it cause me to potentially need different length pushrods for the intake vs exhaust? Will this cause any rocker issues?
I have yet to measure the valve spring height to see if the intakes need to be shimmed up or if the exhausts are too short for the lift I need- Anything in particular I need to watch out for here?
3- The new valves don't have the 2nd groove on the stem for the o-ring seal. Should I be concerned? What kind of seals should I use for this arrangement.

Since I only want to do this once, I'm just being overly cautious with the heads. I was hoping to get some inside from this board before I decide to contact the shop regarding my concerns.
Any advice would be greatly appreciated!
Thanks!
Elm.

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Old 02-22-2006, 08:31 PM
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If the job was done correctly, the stems heights should be equal. Did I hear you say that the heights of the valve stem tips were as much as .125 different?

If the shop had a precision seat cutting machine, there is no reason why they shoudln't all be fairly close.

Even when I use stones, I get them very close to one another. If your stem heights vary a large amount, and you can check that by placing a straight edge accross the valve tips, there can be geometry problems. Check your geometry. There are bandaids for things like this like lash caps. It's a common problem for old heads that have been done several times. I wouldn't put work like that out the door unless it was for a demolition derby car.


Brian
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Old 02-22-2006, 09:11 PM
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Something's wrong! The valves should all be in a line. Did the shop provide the short valves?
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Old 02-23-2006, 06:41 AM
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Short Valves

Yes,
The shop provided the short valves.
When I place the valves in the head and have them fully closed, there is a noticeable difference in valve stem height on the intakes vs the exhaust.
The intakes all line up with each other and the exhausts all line up with each other but the intakes vs exhausts have like an 1/8" height difference.
Since I didn't have them install the seals and springs (I just brought in the bare heads and valves) I didn't notice this difference until I got the heads home.
I'm a little upset at this point that they didn't notice this difference when the work was being done.
Granted, these heads may have been worked several times, but I see no reason for this difference- Valves come in all sorts of stem lengths, don't they?
Guess I need to make a call..
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Old 02-23-2006, 06:47 AM
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If the exhaust seats were sunk they needed replaced. Not having the same tip height is an inconvenience, not a tragedy. It is much better work when they are machined correctly.

But if you need to run these.....

Stem height is only critical when you have non adjustable valves. If you cant get valve stem lengths you need As long as you can get the correct installed height using retainers/locks etc. You can check valve train geometry and do a correction with push rods if needed.

Last edited by Infomaniac; 02-23-2006 at 06:53 AM.
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Old 02-23-2006, 08:33 AM
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I'm a little perplexed as to how he'd end up that short. He either sunk the intakes and left the exhausts really high or the original valves were +.100 longer to start with and the replacement is stock SBC length.

Do you have any calipers around that you could measure the OAL of the two valves?
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Old 02-23-2006, 08:35 AM
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I think I'll have them get the right valves

Since they (the shop) didn't pay attention when they did the initial work, I don't feel compelled to spend more money on messing with different length push rods, lash caps etc.
The valves lined up before I dropped them off, I would expect they should have lined up after. Especially since just getting the correct length valve in the first place would have avoided this issue.
I am bringing these back to the shop for them to fix.
Thank you all for your advice!
Elm.
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Old 02-23-2006, 09:06 AM
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heads

First thing do as Bill asked and let us know the length of the 2 valves. ( in and ex)

It sounds like the heads are still apart???? no springs, retainers??? what valve is higher the intake or exhaust??? lay a staight edge across the valve stems and use some feeler stock and let use know the true amount they are off....

Oh yea if those heads are set up to run rotaters the installed height will be different on the exhaust side.........

Keith
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Old 02-23-2006, 10:20 AM
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The proper valve stem installed height is 1.97" to 2.00". These heads did not use rotators. They screwed up.

tom
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Old 02-23-2006, 08:36 PM
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Update

I guess I feel a LITTLE better.
When I got home this evening, I measured the intake and exhaust valves overall length. The intakes are 4.930 long overall and the new exhausts are 4.900.
It's only .030, so it appears that correct length valves were used.
The larger difference (the 1/8" difference) is when the valves are in the heads- The Intake seats must be sunk a fair amount in relation to the exhausts to cause this discrepancy. Since I would still like them to be even, I am considering having the intake valves replaced as well to get the heights in line. Since the original config had 1.94/1.50 valves and now I have 1.94/1.60- I might as well go for the 2.00/1.60 configuration?
The shop said to bring the heads back and they would do whatever to make it right.
Any thoughts?
Thanks!
Elm.
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Old 02-24-2006, 08:31 AM
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Run, don't walk, them back to the shop.
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