MG-Cars.net

Welcome to our resource for MG Car Information.

Recommendations

Parts

MG parts spares and accessories are available for MG T Series (TA, MG TB, MG TC, MG TD, MG TF), Magnette, MGA, Twin cam, MGB, MGBGT, MGC, MGC GT, MG Midget, Sprite and other MG models from British car spares company LBCarCo.

MG MGB Technical - One noisy tappet

My wifes 79 MGB LE has one very noisy tappet. Have adjusted them to specs, but it still remains noisy, that is much louder than the rest. Tappet noise is part of the MGB engine I know, but this is the first MGB we have owned with this problem. If it is wear, wear in what? Car has done 50.000 miles, 1 previous owner, and is in excellent condition. Of course I could live with it, but find it annoying, and contend there must be a reason. Any suggestions?.
Kim R.
K Rutherford

The lifter could be binding in the bore causing adjustment problems.
The adjustment nut could be coming loose.
The cam lobe could be soft, worn, and collapsed.
You could be improperly adjusting the clearance or adjusting the wrong lifter.
Anyone else have any more potential causes? Hope that's of a little help?

Jeff Schlemmer

Check for irregular/uneven wear on the face of the noisy tappet. This can affect the match of the feeler guage relative to the other tappet surfaces.

Has the offending rocker bush worn more that the others or in an offset pattern?

Valve stems surface wear/tappet offsets?

Adjust the remaining tappets to match?
Roger T

I don't mean to cuss, but my TR4 had a rocker arm that wasn't hitting the valve stem directly on center. This was maybe caused by a combination of a weak spring (between the rockers on the shaft) and lack of use, I presume. There must have been some buildup of gunk on the shaft keeping the rocker just a bit off the center of the valve stem. It was on my list of things to attend to as I did more important things and kept driving it. When I adjusted the valves, I encouraged the rocker back to where it was supposed to be, and it has since quieted down. I was going to look through the parts bin for another spring, but I'll look again at the next valve adjustment, which is probably overdue. It's probably fine now, the oil's not blackening like it used to after an oil change .. something that seems to be a problem on every used car I've owned. Don't people ever change their oil?

Short version, could be an off center rocker arm. Unless the MGB has an overhead cam and you need to mill the top of the head too, per another post.
Tom

Kim

Have you identified the actual tappet that's noisy? The noise may come from wear on the ramp of the cam profile which can wear and cause the cam to slap the follower when opening rather than taking up the free play gradually. To check this you could set that tappet to a very close setting, say 3 thou, for a short trial run to see if the noise disappears.

I'd then compare the lift on that one with others of the same type (inlet / exhaust). A friend had a lobe wear away to the extent it was only lifting halfway. A dial guage would be ideal but if it's bad a steel rule will show it easily enough.

Rich

Rich

I had this noisy tappet noise and was worrying but that was just because my rocker cover was too tigh so after descrewing a bit it wasn't noisy anymore.
Alexia
Alexia

Alexia,
That shouldn't happen.

I would take off the rocker cover and check the tightness of the rocker-shaft pivot bolts. If the tappet noise is reduced when you loosen the rocker cover bolts then it would suggest the rocket-shaft is not fully bolted down.

I would recommend you also re-torque the head bolts whilst you're at it, and then re-set the valve clearances.
James BGT

My roadster has had one noisy tappet for 15 years. At one point I took everything off except the cam but couldn't find any problems. Subsequently I found that when using the usual 'rule of nine' method of adjusting the valves the gap of the back three was still changing at the exact point, which meant the maximum gap (slightly to one side or the other of the exact point) was bigger than the book value. Since I started adjusting them at the maximum clearance point they are quieter, with no evidence of valve burning or recession over 3 or 4 years, but I still have one noisier one. I don't like it either, but until I have to do a full rebuild I'll live with it.
Paul Hunt 2

well James in fact I chenged in the same time my rocker cover and the bolts ... but about the re-torque my head bolts and re-set the valve clearance it's beyond my knowledge !!

thanks anyway and as I have no noise anymore .... let's ride
Alexia

Kim, is the cam in your engine original or a regrind? It is possible that there is a low spot on the cam that can't be adjusted for. As Paul suggests, turn the engine over and recheck your noisy lifter in all possible positions of "closed valve." Finding the lowest spot on the cam should help reduce the noise, if not remove it.
Jeff Schlemmer

One further item to check that nobody has addressed. The tips on both ends of the push rods are spot welded in place. I am not sure about the push rods on the B series engines, but the ones used in the XPAG/XPEG engines in the T series cars have a habbit of breaking the spot welds, allowing the tips to work in and out a very small amount, but enough to cause a tapping sound every time it pushes on the valve. The cure is to have the spot weld redone or get a new push rod. Good luck - Dave
David DuBois

One other thing. The rocker arm lobe where it contacts the valve stem may have worn through the case hardening wearing a groove in the lobe. When adjusting with the conventional method, the feeler gage can bridge this groove giving a false correct setting that is if fact excessive by whetever the worn depth is.
a thought,
Doug
D Sjostrom

Thanks for all the comments, will have time tommorow saturday get at it. Engine is original, PO, the original owner,said the cam has never been replaced. Kim R.
K Rutherford

This thread was discussed on 19/08/2005

MG MGB Technical index

This thread is from the archive. The Live MG MGB Technical BBS is active now.