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MG TD TF 1500 - Valve adjustment will not hold

i am having a time with the valve adjustment on my '50 TD. Finally adjusted the valves to .012, and that is where they should be. (cam was ground to later spec.) Car runs great. The problem is that after about 10 hours of running the valve train is noisy again, and usually I have to "tweek" a couple of valves, and not the same ones all the time.

Does anyone else have this problem? Am I missing something? I know I tighten the jam nuts well.
C.R. Tyrell

Not so easy to adjust them "hot" but I think the adjustment will be more accurate when made with the engine hot.
David Werblow

Doublecheck/retorque head studs, and rocker shaft.

Reground cam- how long has it been in? Were high pressure springs installed? let's hope the lobes aren't disintegrating.

Drain oil and see if silver fines are swirling around when you stir it up.
JIM NORTHRUP SR

C.R.
It's difficult to say that you have a problem with out knowing how noisey is considered noisey,,,and how quiet you are trying to make them.
One thing you might want to check, is the condition of the tops of the push rods,,they might be warn or starting to crack where they are 'bell" shaped.

SPW
STEVE WINCZE

An archive search for

Push rods XPAG

will bring up a discussion about the tops
STEVE WINCZE

Valve adjustment has been done hot. Engine was rebuilt Feb. 2012. I have approx. 6000 mi on it since rebuild... Yes I drive it a lot. Head has not been re-torqued. No high pressure valve springs were used.

I will be checking the oil filter at the next oil change. I was not aware of the pushrod issue.
C.R. Tyrell

Hi Colin, what oil and additives are you using? I have heard guys talking about the lack of zddp and to much detergent causing problems like this. Other than re-checking head bolt torque can't think of anything at the moment.
Don
D Hanna

If it was mine, I'd drain the oil and send it out to be checked for contaminants, mainly metal. We did this at every oil change on our heavy equipment. Amazing what that oil can tell you. This could give you an idea if there is any disintegration of the cam and/or lifters without pulling them. I would say two things could be happening, cam/lifters on their way out and possibly push rod wear. JMHO. PJ
Paul sr

Don, have you done any research in regard to the wives tale about oil additives. i am not aware of any "detergents" in modern oil, only anti dispersants. I am interested in reading anything you may have found.
Cr, when i opened up my engine after purchase about 1/2 the pushrod ends were loose on the tubes and the tubes were wearing down as a result.
Regards, Tom
tom peterson

Don, I have been using GM's EOS with Castrol GTX 20W50. Pushrod ends are all tight (at least the upper ends) I actually did check them at the last valve adjust. It is possible that lifters are degrading. They are new at rebuild, could have a bad one or two. I just cannot account for adjustment going out on different valves.
C.R. Tyrell

Hi Tom, I do not have any first hand knowledge on this subject. A few articles appear to suggest there are problems. I believe that one was posted on the Toronto MG club site under tech tips (mgtoronto.com). Sorry I have not yet figured how to post links using the iPad. I can perhaps email the write up to you if you can not find it.
Don
D Hanna

Colin sounds like oil is not the problem. Did you need to adjust by very much? Are the #3 and #2 going out more than the rest? Both intake and exhaust on same cylinders? Trying to rule out a cooling problem that maybe causing the head to warp. Yes, I agree it is a long shot.
Don
D Hanna

CR, are you sure you are using the same procedure each time you set the lash? are you sure you are setting the valve when its companion valve is full open? regards, tom
tom peterson

Tom; Yes I am... got it down to a science. After I set the valves... everything is great. Valve train sounds like it should and the car hums down the road, with a little valve noise, and lots of power. After about 5-10 hours of driving... things start getting really rattly again.
C.R. Tyrell

CR, sorry to hear that. after you submitting oil for analysis? perhaps dropping the pan to take a peek at the cam shaft is in order. if it is not in the set up..mechanical failure is all that is left. now it is just a matter of determining how catastrophic it is. best of luck. regards, tom
tom peterson

It'd probably be quicker & easier, but not as visible, to pop off rocker arms and pull lifters from the side cover (without losing their order). Our good old Harbor Freight inspection cameras can give a rough view of cam lobes.
JIM NORTHRUP SR

Just one more thought,,,,,After years of adjusting the valves, by me, the PO, and countless mechanics,, the threads on one of the lock nuts broke away,,, they just separated from the nut, and were still in the mating threads of the screw,,,Might something like this be happening to your lock nuts????? Still hanging on so it sees like they are adjusted, but then slipping a bit???? Sounds not likley,, just a thought,,,
STEVE WINCZE

Steve; That is entirely possible. I think that the jam nuts are 8x1mm. I have some that can be turned down if that is the case. Could be time after 63 years to replace them. Can anyone confirm that his would be the size.
C.R. Tyrell

Yes they are 8 X 1.0.
Metric & multi standard components, MMC has thin jam nuts at a very good price, and high quality.
CR you have not stated how much adjustment has been needed.
Len Fanelli
Abingdon Performance


Len Fanelli

I have experienced this problem twice.

The first time, it was a worn lifter; the second time, a worn cam.

But oil quality definitely plays here on the wear between the lifter and the cam lobe. The pressure at that point is extreme and lubrication must be complete and without any abrasion.

Gord Clark
Rockburn, Qué.
Gordon A Clark

Len; Adjustment seems to be a correction of about .002 max, every time, and not on the same adjusters.
C.R. Tyrell

1. You mentioned the cam was reground. That begs the question as the the type of lobe surface with respect to the followers. Did you or cam grinder research the original grind/followers with respect to flat ground lobes vs tapered?

2. It also raises the question of grinding lobes with respect to pushrod lengths and rocker geometry. While on that subject, was head milled?
...was/should rocker shaft be shimmed up?
This shouldn't be responsible for exaggerated wear, as much as the question 1.
JIM NORTHRUP SR

Sorry Jim. Can't answer the questions other than the head was not milled, as it was straight and true. I don't know what the cam was ground to. Other than I started with .019 clearance and now am down to .012 and that seems to be where the engine likes to be. Looks like I might have to pull the tappets this winter and have a look at the cam and lifters.
C.R. Tyrell

This thread was discussed between 30/10/2013 and 02/11/2013

MG TD TF 1500 index

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