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Re: 360 heads redone, valve stem heights are different?
[Re: cudabitten]
#1688828
10/21/14 11:56 PM
10/21/14 11:56 PM
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Joined: Jan 2003
Posts: 5,903
Florida
Locomotion
master
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master
Joined: Jan 2003
Posts: 5,903
Florida
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Ideally, all valves should be the same height. But variances are usually from inconsistent amounts cut when doing the valve job on the seat angles as well as the valve angles. It's not good to "sink" the valves, but sometimes if the seats are all beat up, it is necessary. I don't really know what an "acceptable range" would be. I guess it depends on the person.
Last edited by Locomotion; 10/21/14 11:58 PM.
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Re: 360 heads redone, valve stem heights are different?
[Re: madscientist]
#1688832
10/22/14 09:53 AM
10/22/14 09:53 AM
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Joined: May 2008
Posts: 958
eastern, pa.
cudabitten
OP
super stock
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OP
super stock
Joined: May 2008
Posts: 958
eastern, pa.
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Quote:
Quote:
Is it possible to "fix" this with lash caps? I think I only have one or two rockers that are "really" loose. Some others are loose on the shaft where they can slide side to side.
What rockers do you have. I don't know how you miss by .020-.025 short when doing a valve job. If you sink the valve, you lengthen the stem height.
Exactly. Only thing I can think of is that either he or someone previously re-did the seats on the other valves and now they are high. Or someone replaced a couple valves in the past? I read that valves stems stretch, called "necking", buy I don't think they could stretch that far.
The rockers are LA style, non-adjustable. Motor is a 78.
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Re: 360 heads redone, valve stem heights are different?
[Re: cudabitten]
#1688833
10/22/14 10:04 AM
10/22/14 10:04 AM
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Joined: Oct 2003
Posts: 11,702
W. Kentucky
justinp61
I Live Here
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I Live Here
Joined: Oct 2003
Posts: 11,702
W. Kentucky
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There is a spec for the height from the spring seat to the tip of the valve for a factory iron head and stock length valves. I ran into this years ago with a 440 I built, some of the valves were sank enough that it had a pop caused by the valves being held open. I had to explain to them this wasn't a abc  . P.S. I'd check the spring installed height too.
Last edited by justinp61; 10/22/14 10:07 AM.
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Re: 360 heads redone, valve stem heights are different?
[Re: cudabitten]
#1688837
10/22/14 11:39 AM
10/22/14 11:39 AM
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Joined: Oct 2007
Posts: 4,219
New York
polyspheric
master
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master
Joined: Oct 2007
Posts: 4,219
New York
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The shop screwed up. Unless there's a good reason (such as a big difference in lift intake vs. exhaust) the stems should be the same height. "Different sizes" = he has no idea what he's talking about.
The good news (if any?): the difference is too small to fix with lash caps, which are .050" thick minimum. If you want to take the heads apart you can shorten the taller stems but it's difficult work.
Larger question: how far away is the geo with the stems now?
Boffin Emeritus
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Re: 360 heads redone, valve stem heights are different?
[Re: cudabitten]
#1688839
10/22/14 12:34 PM
10/22/14 12:34 PM
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Joined: Jan 2003
Posts: 75,282
A gulag near you.
JohnRR
I Win
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I Win
Joined: Jan 2003
Posts: 75,282
A gulag near you.
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Quote:
I fired up my 360 after having the heads redone, ( 5 angle grind, new springs installed-comp 901-16, valves refinished, .020 shaved). I was breaking in a new cam, and had at least one rocker knocking noise. I removed the valve cover and found that the valve stems are all a bit different heights on both heads. The two in the front are .025 and .020 lower than the rest. A few others are about .008 lower. I called the shop that did the work and the guy said that mopar exhaust and intake valves are different sizes.
What is the right answer? The guy told me before I bring the heads back to him to check the lifter to make sure it is not collapsed. I did that and they are all fine. I'm not sure I want this guy to do these again. What should I do? Do I need to check spring height as well as valve stem height? What about the geometry in the combustion chamber? If he keeps grinding the seats, isnt that changing?
2 words ...
ADJUSTABLE PUSHRODS ...
I have done this on the last 2 motors I've done for friends that insisted on using stamped rockers so I was able to set the lifter preload to manufacturer of the lifters spec.
Sounds like you have a pretty stockish build so your lifters should have been preload enough that you wouldn't have had an issue with too litle preload, especially on the ones you say are off by .008.
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Re: 360 heads redone, valve stem heights are different?
[Re: cudabitten]
#1688843
10/22/14 05:44 PM
10/22/14 05:44 PM
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Joined: Jan 2003
Posts: 26,530
Rio Linda, CA
John_Kunkel
Too Many Posts
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Too Many Posts
Joined: Jan 2003
Posts: 26,530
Rio Linda, CA
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When I was taught to do valve jobs it was accepted practice to adjust the valve stem length so that all the valve stem tips were at the same height....there is an attachment on the valve grinder for grinding the valve stem ends. Some FSM's show a tool that is used to measure the height of the installed valve stem tip above the spring seat.
A good machinist will deliver heads that have the correct valve stem height and equal heights so that a straight edge laid across the stem tips will show no daylight.
The INTERNET, the MISinformation superhighway
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Re: 360 heads redone, valve stem heights are different?
[Re: John_Kunkel]
#1688845
10/22/14 07:30 PM
10/22/14 07:30 PM
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Joined: Oct 2003
Posts: 11,702
W. Kentucky
justinp61
I Live Here
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I Live Here
Joined: Oct 2003
Posts: 11,702
W. Kentucky
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Quote:
A good machinist will deliver heads that have the correct valve stem height and equal heights so that a straight edge laid across the stem tips will show no daylight.
Exactly!
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