MG-Cars.info

Welcome to our Site for MG, Triumph and Austin-Healey Car Information.

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 TD TF 1500 - Rocker arms restoration comments pros & cons

It is now time to do what I have been putting off for years, only because the PO (a gorilla) put the jam nut on so tight. I have tried to adjust them but the screws are so tight they won't even budge. I have read over the years about NOT enlarging the oil line that feeds the shaft but that one should chamfer slightly the top of the hole to catch a little more oil down to the bushing. Is there a 'good' way to get the adjusting screws out, other than vice grips on the ball end & should the threads be 'chased' before installing new ones ? Is there a source for these other than Moss. Any and ALL comments are welcome, I want to do this right the first time and only once. Many thanks. Sam
SW SAM

Sam, what hole are you talking about chamfering?
Do you have a set of whitworth wrenches? I thought they are whitworth, but perhaps I am mistaken. As you stated, you need to get those loose to adjust the tappets as per the engine shop manual.

Regards, Tom
tm peterson

ASL
http://abingdonspares.com/engine-internal/

Do not run a tap through the rocker, use a thread chaser only if needed. Threads are 8 X 1.0
Len Fanelli

Sam,

There is no reason to hold the ball of the adjusting screws to get them out. The adjusting screws screw into the rocker arm and the nut (jam, as it's called) is tightened down around the protruding part of the adjusting screw to keep it from moving once set. All you should need to do is use the correct wrench and unloosen the jam nut.

If this isn't working for you you need to provide a bit more information about what is happening.

Gene
Gene Gillam

The locking nuts are often rounded over. The best way to deal with these, and ones that are very tight, is remove the rocker assembly and then grip the nuts in a vice. You can then apply a strong turning force with a large adjustable spanner on the rocker itself.

Jan T
J Targosz

I thought the finish on the rockers was ugly, so I decided to polish them.
My advice now is; don't. It takes hours and you don't see them again.

Jan's advice is correct; it is how I saved my rockers.
The oil goes through the shaft and then through the rockers. The hole you probably mean is the exit, not the entry for the oil.

Willem van der Veer

Sam, there's another option that you might want to consider. An outfit in CA (http://www.rockerarms.com/index.html) specializes in totally rebuilding rocker assemblies. I've had excellent results using them. Only caveats I've run into is to check the order of the arms on the finished product and to replace the jam nuts with Whitworth sized nuts. Bud
Bud Krueger

You said the jam nuts are tight. You have to take them off first, then the screw/ball should be totally loose. I have found several where the threads are stretched (ie the adjuster is ready to break), so check that when you get them apart. George
George Butz

Wasn't there a school of thought to blocking off the hole in the rocker to force the oil to leave via the bushings and give better liberation?
I understand lot of oil goes to the rockers and this helps the cam followers (tappets) as it drains down through the head and block.
I have not done this on my rockers but it kind of makes some sense. If you have ever run the car with the rocker box off you will no doubt find as I did, its best to wear a plastic mac and cover your wings in rags. As it tends to spray quite a bit. Blocking the holes on top might make observing the pushrods rotating a little less messy. Does anyone have experience of doing this?
As for the adjustment - the ball screw has a screw driver slot in the top, to allow you to hold the screw whilst you nip up the jam nut with a spanner. It should not need unnecessary force and be done when the engine is at operating temp.

Rod
R D Jones - Ex Pat

M8X1.0 threads on those nuts, dont matter if they are loosened or tightened with a Whitworth of metric wrench that fits. Jam nuts dont got much thread to grip so get some new ones if they are worn. And adjust those valves.
Sam Coleman

Willem,

I have to say that I am very impressed by your polished rockers. Smoothing of rough castings is one thing, but polishing at the level you have achieved is something else. Pointless no doubt to many, but I respect your philosophy.

Cheers, Michael
M R Calvert

Rod,
I welded up the holes in the rockers many years ago and have suffered no increased wear. I gained 5 psi on the gauge, don't get kidded as the rockers still throw an amazing amount of oil around with the cover off.
I blocked mine as I was told in the sixties by an old MG mechanic that after an engine was run in they drove a mini ball bearing into the hole and staked it in.
I believe the TA rockers do not have a hole at all.
Ray TF 2884
Ray Lee

WOW, so much for old wives tales. The problem here as I said was not the jam nut but the adjusting screw. The jam nuts were abused and rounded off but a good pair of vise grips and no problem. The real problem is/was the adjusting screw, it won't turn in or out. Seems the screw or the rocker threads may me seizing up. In addition the screwdriver slots in the adjusting screws are either broken or spread open from other attempts to adjust them. I was left with NO choice but to back them out with vice grips. I have tried to run a tap thru the M8-1 hole but only get three turns before the tap binds. What is the difference between a 'thread chaser' and a 'tap'? The most important thing I have learned from this thread is that the oil hole is NOT to feed oil to the bush it is actually the exit hole. Oil is pumped into and thru the shaft to the bush and then exits, I never thought about that, so a chamfered hole is pointless. I will also need to take care in checking the wear on the bushes now that I understand their importance. Many thanks to all that responded and you share of knowledge. Cheers Sam
SW SAM

In regard to blocking the rocker holes, are you sure that the professional designers made a mistake? The oil flow in an engine serves two purposes, lubrication and cooling. You are losing a lot of cooling effect by restricting the volume of oil flow to the upper engine.
Ray's comment about the TA rockers seems more likely a statement the the professional engineers who designed this engine calculated that this was a necessary additional matching process rather than a mistake.
I am biased towards trusting the combined education and decades of experience the designers and builders put into these cars, particularly when what they did involved adding extra matching processes.
Regards, Tom
tm peterson

Got the picture now. Make sure you have the correct tap. Try a 8x1.0mm bolt and see if that threads in. Pretty hard to mess up the threads in the rockers but maybe someone did. George
George Butz

A couple of comments:

1) The adjusters are supposed to be tight in the rockers; running a tap through them will only remove precious metal. At the very best, sand-blast a used 8x1mm tap until the threads are no longer sharp, and use that. One customer ran taps through all his head stud holes in the block, and four pulled out as he tightened them. I had to put inserts in all OF THEM.

DON'T use a sharp tap to clean out engine holes.

2) Polishing the rockers is something racers used to do to promote quicker oil return; fewer nooks and crannies to hold the oil. But, like the sump, the roughness of the metal acts like a heat sink, and much heat is wicked off original rockers. Polished rockers, like a polished sump, WILL increase operating temperatures, and decrease the lubricity of the oil.

Tom Lange
MGT Repair
t lange

Just checked the original bushes which I kept after replacing with new, a few months ago. The oil hole does not line up with the scroll. Oil will have to squeeze between the bush and shaft before it can exit from the hole in the rocker. Makes sense if you think about it. There are two lengths of bush, long ones and short ones. Don't ask me how I know! I now have a spare set of short ones and if anyone needs them they are available free of charge. Possibly only of interest to UK subscribers since they are inexpensive and postage overseas would be more than their cost.

Jan T
J Targosz

The adjusting screws seize in the rocker due to deformed or stretched threads.
A thread chaser just straightens out the existing threads, it does not cut new threads.
Len Fanelli

OK Len, then a semi-worn tap could be used as a 'chaser' then as it isn't cutting 'new' threads just restoring them to better condition. Yes, I think the gorilla before me didn't have a clue. Sam
SW SAM

This all brings to light the latest offering by ASL.

http://abingdonspares.com/performance-parts/

They are offering a roller rocker, the geometry of which is curious. It appears to be straight which is quite different to the standard rocker.

Is there anybody out there who has a set of these?

Gord Clark
Rockburn, Qué.
Gord Clark

Gord, I think you'll find that Abingdon Performance is our friend Len Fanelli's line of products. Bud
Bud Krueger

Gord, I think you'll find that Abingdon Performance is our good friend Len Fanelli's line. Bud
Bud Krueger

Thank you all for your feedback, they made this project enjoyable. The adjusting screws didn't come out without a fight, five of eight died. The machine shop reground the rocker 'tips' but said the wheel touched the rocker body and they recommend replacing 4 of the arms for safety reasons. Does anyone have any used rocker arms available ? Please drop me a note off-group if you would. Again many thanks for your input. Sam
SW SAM

Yes Gord & Bud, I have given ASL permission to advertise some of my products.
Before anyone runs a thread chaser thru the rocker arms, use a thread chaser on the screws.
A whet stone can be used for those who want to DIY to resurface the arm tips.
Len Fanelli

Sam - don't lose sight of the fact that the rocker tips are hardened, and just re-grinding them can make matters worse by grinding thru the hardened area. The right way to do it is to have the tips welded up with Stellite welding materials, and then have them re-profiled. Chances are that they have been ground down before, so Stellite welding is the best method.Tom Lange
MGT Repair
t lange

Hi Tom - I agree with one point, Stellite is the way to go I'll check on pricing that. As to the rocker tips being hardened, I don't think so. If they were they wouldn't be 'worn in' and need to be profiled. You can also take a file to the rocker 'crown' and it will 'score' the metal. Sam
SW SAM

Sam - yes, I see your point, and agree, after thinking for a few seconds. The added Stellite is the hard part needing to be re-profiled...

Tom
t lange

This thread was discussed between 06/11/2016 and 17/11/2016

MG TD TF 1500 index

This thread is from the archives. Join the live MG TD TF 1500 BBS now