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MG MGB Technical - Valve Tappet Adjustment Trouble

I have a 1974 MGB and the valves are quite noisey. I have adjusted them now for the 3rd time and I can't get them quite. Each time, I follow the repair manual to the tee. I make sure the valve is closed, I adjust to .015 cold / .013 hot. I tsrat the car, and tap, tap, tap. Each time I have thought, "well, I must have missed one, or maybe I didn't get it just right", but I just finished doing it again, and they still tap. Not extremely loud, but much louder than others I see at car shows.

The engine has around 50K miles. What am I missing here???
Tommy

The tappets should make some noise, if yours are too noisy the rocker arm surface that contacts the valve stems may be worn, consequently a feeler gauge will measure the unworn area but not the true gap between the rocker arm and the valve stem tip. You can check the rocker arms by loosening the adjuster and slide the rocker arm over enough to feel if there is a worn area. You should be able to feel the wear ridge with your finger nails or you can observe them with a small mirror. A worn rocker shaft and rocker bushings could also make them noisy. If the valve clearances are changing shortly after adjustment you may have some severe wear in the exhaust valve seats. I also hear cars at shows that have no noticable tappet noise. FWIW, Clifton
Clifton Gordon

I had this problem -- the rocker assembly
had about 60K miles on it and the shaft/bushings
were worn enough to cause significant noise.
Not enough for a noticeable wear ridge on the
shaft, but there was a lot of play when twisting
the arms back and forth.

A rebuilt rocker assembly made the tappets
much quieter, although I think there's an increase
in the noise level after a few thousand miles.
I would consider the tuftrided rocker shaft the
next time I take off the rocker assembly.
Ronald

Tom-"closed"? Rule of 9. Vic
vem myers

Hi Vem, Yes, "closed". You adjust the "closed" valve, not the open one. The open valve is under pressure from the valve spring. The closed valve has the preassure off, thus you can make the adjustment.

I am very aware of the Rule of 9. This is just where when a valve is "open", you then adjust the corresponding valve equaling 9, which will be "closed".
i.e., if #1 valve is "open", you would adjust #8. When #2 valve is "open", you would adjust #7, etc. The rule of nine is so you can make the fewest turns of the engine while adjusting the valves. The sequence goes,

Open Adjust
8 1
6 3
4 5
7 2
1 8
3 6
5 4
2 7

However, you always adjust the "closed" valve.
Tommy

Tommy,

How wide are the feelers you are using?

The rocker arm wears a "pit" and a wide guage will bridge the pit and give a false reading.

If you are using feelers with tips wider than 1/4 inch then you will suffer from this problem.
Chris at Octarine Services

Chris, I am using a fairly wide feeler guage. It's a generic one that you pick up at most any autp paorts store. It is close to 1/2" wide. The worn rockers may be the problem. I just looked them up in the Moss and VB catalogs. WOW!!! They are expensive. I may hev to just live with it a while longer. the cars runs great and the noise is not excessively loud.

So I assume that when I DO make the replacement that I should go ahead and replace the rocker arms, Rocker arm bushings, tappets, and the push rods all at one time?

Tommy

Mine has tapped for the last 14 years and 40k miles. At one time I had the rockers, pushrods and tappets out to try and fine where it was coming from to no avail so I live with it. However I did have problems getting repeatable clearances for many years - adjust, spin engine, check and they had changed again - until I discovered that at the strict 'rule of nine point' on some valves towards the back of the engine the gap was still changing so unless I checked at the exact same point every time I got different readings. Since then I have adjusted at the position of maximum gap which is slightly to one side or other of the strictly exact point. It did make them a bit quieter but I still have the tap. I did wonder if the now slightly smaller gap might contribute to valve seat recession but they haven't changed over two years.

You can compensate for dished rocker faces with a ClickAdjust or similar (reputedly, I have used one), but once you have worn through the case-hardening further wear will probably be quite rapid, needing rocker replacement.
Paul Hunt

Tommy, you can get a complete rebuilt
rocker assembly for less than $200 -- I got
mine from www.propermg.com (not an endorsement,
just a customer.) However, check the rocker tips
carefully for proper machining before installation.
I think Clifton warned about this potential problem
in an earlier post.
Ronald

Tommy,

If you have a Dremel the solution is easy.

It requires removal of the rocker assembly and the rocker arms from the shaft, using a sanding drum on the Dremel just stroke the rocker pads from front to back of the pad till the depression disappears.

If you want, you can replace the shaft with a new one at the same time - not a perfect solution but it will reduce the play in the assembly dramatically.
Chris at Octarine Services

In addition to Chris's suggestions, take a look at the push rod ends. Each end of the pushrods are spot welded into the rod. these spot welds sometimes break loose, leaving the end to rattle around in the rod and cause a louder than normal tapping. Rewelding the ends will quite them down. Good luck - Dave
David DuBois

David,

standard B pushrods are solid - you only get ends on tubular rods and usually they are a press fit - no welds.
Chris at Octarine Services

Chris, if the rocker arms were worn, causing divits, wouldn't the rocker arm still have a lot of movement / rattle, even after I had adjusted them? When you grasp the rocker arm after adjusting, there seems to be almost no movement or rattle. But when you start the engine, you hear the rattle. I would think if the problem was wear / worn dimples in the rocker arms that you wouls still "feel" the movement prior to starting.

I would hate to tear it down and replace the rocker assembly if I don't need to.

Tommy

Yes you should still feel the movement but we are only talking a couple of thou from noisy to quiet.

As an experiment, try resetting the valve clearance to 12 thou inlet and exhaust and see if the rattle stays or goes.

If it stays then use a piece of narrow bore pipe as a "stethoscope" to check whether the noise is coming from the valve end of the rocker or the shaft or the pushrod end.

Also check if it is one or more rockers making the noise.
Chris at Octarine Services

I wish there was a way to tell someone exactly how much noise to expect. I've adjusted mine several times and still have a very audible ticking at idle that is quickly drowned out when revved. The engine runs greats, pulls good and has been ticking like this for 7 years. I guess it's normal but often wonder.
Brad Batchelor

Had the same problem. So got a gunsons Click adjuster. After a bit of trial & error worked it out to be 7 clicks. Tappets now quiter than I have ever heard them, but more importantly the car seemed to be a whole lot smoother and pulled a lot better. Part from Halfords £17 if I remember right.
rgds Bob
R. C. Elwell

This thread was discussed between 21/08/2004 and 23/08/2004

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