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Worn valve stem....caused by the rocker??
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Author:  Mick [ Wed Jun 23, 2010 6:49 pm ]
Post subject:  Worn valve stem....caused by the rocker??
I am officially on holidays having finished the last of the semester exams this evening, so I thought I would do a bit of a tune up as it's been about 3 or 4 thousand since the last.

I decided to look at the gaps after the long trip to Hay and back the other weekend, I noticed something odd with cylinder 3's exhaust valve. Its gap was massive. I took the rockers off because it didn't look or feel right to me and found the pictures below.

The stem has had the top worn down, with an angle leaning towards the front of the car with some damage to the foot of the rocker as well. I'm not sure what has caused this as the operating conditions on that valve is identical to the other exhaust valves. Clearly the head will need to come off and the valve replaced, an easy enough job, and I will replace the rocker as well.

The valves were new last year when I rebuilt a 12g940 to replace the original serviceable yet fragile AEG163 head.

Can anyone identify what has caused this?

Image

Image
Author:  VulcanBB18 [ Wed Jun 23, 2010 7:01 pm ]
Post subject: 
Those who have been looking at these engines much longer than me will probably shoot me down, but anyway,,,

Two things stick out to me in those photos - one is the post with what looks like lots of wear around the stud hole, is it an alloy type?

The other is the top of the spring around the retainer - it seems to be sticking out a lot more than I'm accustomed to. Is the valve bent??

just wild stabs...

cheers

Jacob
Author:  GT mowog [ Wed Jun 23, 2010 7:02 pm ]
Post subject: 
From the look of the bur over the valve tip it appears that it is soft. Have you tried the 'file' hardness test on it?

Is the bush and / or shaft in the rocker worn? If it is it won't let the oil go where it should.

<EDIT> on a second look it appears very much that the rocker tip has been overhanging - at some point in it's travel - the valve tip.
Author:  Mick [ Wed Jun 23, 2010 7:14 pm ]
Post subject: 
Thanks, the wear around the rocker pillar stud hole is an optical illusion. It is no more than a mark. The rockers and steel pillars came as a set of forged 1.5:1 rockers. They've seen service on four cars now, I swap them from feature donk to feature donk as I go along. Its a little sad that one is damaged after so much service over so many years :(

The rocker shaft was new with the engine and is still in good order it appears with no wear detectable if I move the rocker sideways on the shaft.

And yes, I can quite successfully take metal off the top of the valve with a file. I can remove a reasonable amount of metal with only a few strokes of a 2nd cut file..
Author:  drmini in aust [ Wed Jun 23, 2010 7:23 pm ]
Post subject: 
I run those same forged 1.5 rockers on my 1360, after using a VP3 then an RE13 then a RE282 cam they are still fine, I think. No funny noises yet.
I'm a bit more concerned with that valve stem wear, some valves have hardened (stellite?) tips and some are plain, some race valves are just S/S.
Can you ID what the ex valves are and where they came from?
Author:  GT mowog [ Wed Jun 23, 2010 7:24 pm ]
Post subject: 
Arrrrr.........

Mick wrote:
...... The rockers and steel pillars came as a set of forged 1.5:1 rockers.

And yes, I can quite successfully take metal off the top of the valve with a file. I can remove a reasonable amount of metal wit honly a few strokes of a 2nd cut file..


I see it now. It is absolutely necessary to check these when fitting each and every time and every rocker that that don't go 'over the edge' so to speak.....

......and the valve shouldn't be that soft.

You'll be getting the rocker tip re-ground, yeah? Shouldn't be a need to replace, they usually rip ya pretty hard for 1 rocker.....

<EDIT> could also possibly benifit from a shim between the rocker and the post, but need to check where the pushrod then sits.
Author:  Mick [ Wed Jun 23, 2010 7:59 pm ]
Post subject: 
I will, I have a set of rebuilt forged S rockers here as it happens (whats the chances hey :P ) so I will put these on the back burner and put the rebuilt set on. I'll motor around the big city tommorrow and pick up a new head gasket and valve from one of the local gurus. I wonder if Josh is at Miniimports tommorrow. He wants me to come and let him into the Cadbury factory shop... :P

The valve was a standard replacement, 3 of the others show a little scraping, but nothing like this one
http://www.minispares.com/Product.aspx? ... 608&title=
Author:  GT mowog [ Wed Jun 23, 2010 8:04 pm ]
Post subject: 
Mick wrote:
I will, I have a set of rebuilt forged S rockers here as it happens (whats the chances hey :P ) so I will put these on the back burner and put the rebuilt set on.


Mick, you haven't used a set of forged Cooper S Rockers with Pillars for a 1.5:1 ratio set have you?
Author:  Mick [ Wed Jun 23, 2010 8:06 pm ]
Post subject: 
Nah, the 1.5 rockers go with the 1.5 steel offset pillars, being bright steel I'm glad they're pretty easy to keep together.

The S rockers are kept with the correct pillars as well.
Author:  GT mowog [ Wed Jun 23, 2010 8:09 pm ]
Post subject: 
Mick wrote:
Nah, the 1.5 rockers go with the 1.5 steel offset pillars, being bright steel I'm glad they're pretty easy to keep together.

The S rockers are kept with the correct pillars as well.


8)
Author:  drmini in aust [ Wed Jun 23, 2010 8:11 pm ]
Post subject: 
Mick wrote:
Nah, the 1.5 rockers go with the 1.5 steel offset pillars, being bright steel I'm glad they're pretty easy to keep together.

The S rockers are kept with the correct pillars as well.

If you are going to run the S rockers and stock pillars with a hi-lift cam, have a good squiz at how the rocker wipes the valve stem at full lift.
Many people (including Hammill) suggest removing 1.0mm (.040") from the bottom of the pillars when you do this. I find it's essential to do with the A+ sintered rockers, otherwise they wipe right over the rocker tip.
Author:  Mick [ Wed Jun 23, 2010 8:17 pm ]
Post subject: 
So I have one of three thoughts here, correct me on what would be the most likely.

1. The gap on that rocker perhaps closed up and over extended the valve

2. The valve stem is improperly hardened

3. Carnies (Circus folk. Nomads, you know. Smell like cabbage. Small hands..)

4. Other unspecified.
Author:  GT mowog [ Wed Jun 23, 2010 8:24 pm ]
Post subject: 
Mick wrote:
So I have one of three thoughts here, correct me on what would be the most likely.

1. The gap on that rocker perhaps closed up and over extended the valve

2. The valve stem is improperly hardened

3. Carnies (Circus folk. Nomads, you know. Smell like cabbage. Small hands..)

4. Other unspecified.


items 2 and 4.

Unspecified - poor rocker geometry - thr rocker pad overhung the valve tip. Not caused by clearance closing up, just typical of the forged rocker.
Author:  Mick [ Wed Jun 23, 2010 8:26 pm ]
Post subject: 
Off with its head!
Author:  GT mowog [ Wed Jun 23, 2010 8:29 pm ]
Post subject: 
Mick wrote:
Off with its head!


Just be sure not to re-fit with the presently available BK450.......
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