Replacing Valve Stem Seals (in situ) Pitfalls?

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A new seal won't do squat if the stem-to-guide clearance is too large. I've often wondered if my intake valve stem seals prevent lubrication from reaching the guides and cause premature wear?
 
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Danno said:
A new seal won't do squat if the stem-to-guide clearance is too large. I've often wondered if my intake valve stem seals prevent lubrication from reaching the guides and cause premature wear?
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Ajs and matchless have holes drilled in the valve guides to allow lubrication
Just on the exhaust guides I believe?
 
Danno said:
A new seal won't do squat if the stem-to-guide clearance is too large. I've often wondered if my intake valve stem seals prevent lubrication from reaching the guides and cause premature wear?
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I wonder the same thing, especially with iron guides. Purely guessing but I figure that they last about as long as the exhaust - the exhaust environment is way worse, but the intake gets less lube.

Someday I'm going to experiment with reducing the overall oil flow, turning at least the intake rocker spindles the "wrong" way, and getting rid of the seals. AFAIK, the reason we need the seals is because we flood the intake side with oil often reaching higher than the top of the guides.

Triumph and others need no seals - they have minimal oil going to the rockers and the drains are huge compared to the single small drain in the Norton head on the intake side.
 
marshg246 said:
I wonder the same thing, especially with iron guides. Purely guessing but I figure that they last about as long as the exhaust - the exhaust environment is way worse, but the intake gets less lube.

Someday I'm going to experiment with reducing the overall oil flow, turning at least the intake rocker spindles the "wrong" way, and getting rid of the seals. AFAIK, the reason we need the seals is because we flood the intake side with oil often reaching higher than the top of the guides.

Triumph and others need no seals - they have minimal oil going to the rockers and the drains are huge compared to the single small drain in the Norton head on the intake side.
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The dunstall commandos had the rocker feed reduced to 20 thou
 
baz said:
The only thing that amazes me is Norton commandos didn't even have valve guide seals for the first few years!
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And neither did early '60s Harley Davidson Big Twins and "acceptable" oil consumption was a quart of oil in 250 miles.

Early SB Chevy V8s did not have valve seals and when the guides got worn it was not unusual to add a quart of oil at every fill-up.
 
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Dan1950 said:
And neither did early '60s Harley Davidson Big Twins and "acceptable" oil consumption was a quart of oil in 250 miles.

Early SB Chevy V8s did not have valve seals and when the guides got worn it was not unusual to add a quart of oil at every fill-up.
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That's a hell of a lot of oil!!!
 
Danno said:
A new seal won't do squat if the stem-to-guide clearance is too large. I've often wondered if my intake valve stem seals prevent lubrication from reaching the guides and cause premature wear?
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It is not likely that only one guide is worn but one seal failing is a possibility.
 
marshg246 said:
I wonder the same thing, especially with iron guides. Purely guessing but I figure that they last about as long as the exhaust - the exhaust environment is way worse, but the intake gets less lube.

Someday I'm going to experiment with reducing the overall oil flow, turning at least the intake rocker spindles the "wrong" way, and getting rid of the seals. AFAIK, the reason we need the seals is because we flood the intake side with oil often reaching higher than the top of the guides.

Triumph and others need no seals - they have minimal oil going to the rockers and the drains are huge compared to the single small drain in the Norton head on the intake side.
Click to expand...
Oil is important for cooling as well as lubrication though Greg. So I’d vote for more oil with seals, over less oil with no seals.
 
Fast Eddie said:
Oil is important for cooling as well as lubrication though Greg. So I’d vote for more oil with seals, over less oil with no seals.
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No disagreement there; IMHO, the real issue is flooding the intake area and thereby requiring seals.

IMHO there are four choices:
1) Reduce the amount oil so the intake drain can keep up and eliminate the seals
2) Increase the drain size - hard to do but may be possible and eliminate the seals.
3) Add an intake drain on the drive side - again, hard to do but may be possible and eliminate the seals.
4) Live with it as designed but do nothing to make it worse (installing the spindles towards the center, opening the oil feed holes to the spindles for better alignment, etc.)
 
Dan1950 said:
Why is everyone thinking that this is a brand new build when I have repeatedly cited otherwise?

My rational is that I do not want to do a rebuild at this point in time and I want to see if a quick fix can reduce oil consumption to a point where it is not a nuisance when riding this season.

Ideally, if the head comes off the cases will be split. I would not want to R&R the head for valve seal replacement only to remove it again this coming winter.
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Dan, If your rational is a quick fix, have you had the cover off yet to see if the seal has just popped off?
 
marshg246 said:
No disagreement there; IMHO, the real issue is flooding the intake area and thereby requiring seals.

IMHO there are four choices:
1) Reduce the amount oil so the intake drain can keep up and eliminate the seals
2) Increase the drain size - hard to do but may be possible and eliminate the seals.
3) Add an intake drain on the drive side - again, hard to do but may be possible and eliminate the seals.
4) Live with it as designed but do nothing to make it worse (installing the spindles towards the center, opening the oil feed holes to the spindles for better alignment, etc.)
Click to expand...

A bigger / external drain is possible, Maney did it on his stage 3 heads because his porting would break into the stock drain hole…

Replacing Valve Stem Seals (in situ) Pitfalls?Replacing Valve Stem Seals (in situ) Pitfalls?
 
David Sundquist has done an exterior oil drain from intake rocker box drain to his cam rather than the factory "wasted oil draining to TC/sump":

 
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I could interpret your reasons for doing an in situ seal change as:

'You don't want to take the head off to do the job, because you don't want to find, piston ring and bore wear that would demand a full strip and rebuild! Thus losing you a riding season.'

All ways round this is a little head in the sand. I usually work on the bench when engine building will have the head on and off several times in the afternoon, but in the frame it will take much longer, but I reckon I can remove and replace a head within a day, working at a leisurely pace as long as I am not fitting new valves or springs, take the weekend.

You can still ignore the piston and bore wear if you want! :rolleyes:

But at least you will know where you stand on this.

300 miles a quart is way worse than my 4 cylinder air cooled 1200 Yamaha with 168K miles on it. And half of the oil use on that was that they typically boil the stuff and it evaporates......

BTW, I hope that slide hammer has 5/16" x 26 tpi cycle thread the other end, not the coarse thread we can see......and don't be too surprised if it doesn't work right away!
 
Tornado said:
David Sundquist has done an exterior oil drain from intake rocker box drain to his cam rather than the factory "wasted oil draining to TC/sump":

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Can’t argue against the cam liking more oil!

But my engine doesn’t breath into the timing chest, so without that oil drain feeding it, it’d be horribly dry in there !
 
Didn't Jim Comstock arrange a oil feed to the cam lobes and say he never saw it made any difference in wear or am I off the target on this?
 
Tornado said:
There are a few older threads on this procedure. Ludwig's write up and tool cobbling guide for in situ seal replacement:

I used his homemade compressor but went with the "rope trick" method to hold the valves up, not his sparkplug hole-holder.
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Thank you.I saved that.Ian
 
Onder said:
Didn't Jim Comstock arrange a oil feed to the cam lobes and say he never saw it made any difference in wear or am I off the target on this?
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That rings a bell. And makes sense.

Unless oil is introduced to the cam lobe at the point it meets the follower, I would suggest it’s just going to get flung off.

Imagine spinning a cam up in a lathe and squiring oil on it… it’s just gonna fling off everywhere !

Hence cutting fluids are directed at the point of cutting.
 
Sundquist's oil fed cam set up is interesting, would like to find that mention by JC for reference, but I wonder if a gravity feed from an exterior inlet drain would accomplish something similar, but without compromising actual oil feed pressure?
 
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