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MG MGA - Faulty Clutch release bearings

This was delivered by High Gear as part of a five speed kit. Makers mark is Powertune. The carbon ring was loose in the bag. The ring is soft enough to be marked with a ballpoint pen. I am sure Peter will replace it, this is just a warning to others not to use this part. I have installed another kit from Peter where the bearing is now making a howling noise so expect that this one too is spinning in the casing.

Fitted in a clutch fork it binds one way in, the other way it's fine, so there is also some dimensional variance in the casting. There's no sign of any bonding pin or material in the housing


Dominic Clancy

Dominic,
I fitted one of Peters release bearings when I fitted my 5 speed gear box and it was worn down to the casing within 1000 miles. Have now fitted a roller bearing one which has now covered just over 1000 miles
Regards

David
D M SPEAK

I changed mine about 5 years using one from Moss. All fine after about 20k miles.

Paul
Paul Dean

I bought a brand new roller release bearing when i did an engine swap a year ago. When i found that i was supposed to grind a couple of grooves in the surface of the spigot shaft to locate the CRBs retaining clips, I chickened out and fitted a new standard type CRB instead.

The old one ( from Moss) was only slightly worn after 25000 miles but it seemed sensible to fit a new one.

Dominic, did you get anywhere with your concentric slave cylinder research?

Colyn
Colyn Firth

Problems with carbon release bearings are not uncommon across the BMC range.
With 948 / 1098 Sprites and midgets one solution is to machine the casting to accept a deep groove ball bearing onto which is then fitted a steel faceplate. Unfortunately not all castings are suitable for modification.
For 1275 Sprites and Midgets a different approach can be used with a redesign using a modern release bearing on a custom mount.
In all cases the new bearing is a direct swap for the carbon release without further modifications.
Alan


Alan Anstead

My current carbon release bearing (complete MGB clutch kit) came from Moss, early December 2012, now with 150,000 miles on it, still doing okay. Not the MGA part, but I suspect they would have the same source. Not sure about same source five years later, but I have never gotten a bad carbon bearing from Moss in 30 years.
barneymg

Just to correct my post above about fitting a roller release bearing, the modification I mentioned was to be made to the clutch release arm and not the spigot bearing. Sorry guys.
Cheers
Colyn
Colyn Firth

Colyn

It was the clutch release arm bush that went early on my 5-speed causing the clutch thrust bearing to run off centre with lots of shuddering on clutch engagement. See photo. No Problems in last 10 years with either new item.

Steve

Steve Gyles

Hi Colyn

It is sitting on the bench waiting for a visit from the Hon. Mr. Betson. He will be bringing a 1950 engine to supercharger spec, and the new slave will go in with that. I don't expect to fit it before the autumn.

This kit has to go in in the next couple of weeks, I was just waiting for the right angle gearbox for the speedo cable, which arrived today.

Peter Gamble says the bearing isn't from him so I have had another look at the pile of paperwork that i have sitting to be looked at, and it's from Brown & Gammons (now I remember the were the only ones with a new MGA Clutch kit in stock when I was ordering all the stuff for this project), so I'll give them a call tomorrow.
Dominic Clancy

And official apologies to Peter for casting aspersions - he was really nice on the phone when I called him to ask if it was he or Chris Betson that supplied it and all the time it was neither of them

Dominic Clancy

Wow Dominic, a 1950cc engine with supercharger! Is it going into your car?

I thought that my 1950cc engine with a Weber 45 DCOE was awesome, I cant imagine what performance you are going to get if you supercharge it!

My engine develops around 140 bhp with incredible torque and it is just brilliant to drive,but what does really amaze me is just how well the MGA copes with all that extra power.
My car has standard suspension apart from Armstrong adjustable lever arm rear shock absorbers and it handles the power like it was designed for it. I thought it would need anti-tramp bars and/or a panhard rod on the rear axle but it seems to be just fine as it is.

When you consider that the original 1500 MGA had half the power that my engine has, it is an incredible car.

Cheers
Colyn
Colyn Firth

Colyn

Yes

My thoughts exactly - shall we say I'm expecting it to be nice. And with his Betsonship behind the engine I am expecting no reliability problems.

Timing will be managed by an electronic unit with a boost sensor
https://www.cbperformance.com/product-p/2013.htm

This is already used by a member on the other place in a similar build engine in an MGB, whose timing map I intend to reuse.
http://www.mgexp.com/phorum/read.php?1,2993783

Am I committing a cardinal sin by posting this link to the dark side ? After years of posting here I don't know if we even have a moderator who could ban me for such transgressions? Happily I don't think we have ever really needed one! That must be a record in such forums these days, and a real testament to our band of MG brothers that we have no trolls and leave politics and religion elsewhere!


Dominic Clancy

Sorry if this is wandering off topic but will your programmable ignition set up have a knock sensor built in?
I would imagine that with all that power on tap, you will need someone with as much expertise as Chris Betson on hand to be able to set up the ignition timing so that you have a safe starting point for the timing.

Let us know how it goes.
Cheers
Colyn
Colyn Firth

No, but backing off the timing under boost pressure avoids the pre-detonation issue better than a knock sensor in an engine that rattles anyway and often confuses a knock sensor (I had a knock sensor when i first went the SC route using a non-programmable box - it didn't work very well and retarded the timing excessively whenever I put the pedal to the wood).

The carb is also a major factor in avoiding pre-detonation or knocking. If the engine is running lean then no amount of tech is going to avoid terminal engine failure. I am using the same carb and needle as the Moss SC kit for the MGB, and the CB black box gives me a lot more control over timing under boost than a standard dizzy, so I think the potential problems can be avoided.

How did we get here from comments on crap quality on a standard clutch bearing????
Dominic Clancy

Apologies for wandering so far off topic, my fault.

I do tend to get a bit carried away when someone starts talking about power tuning MG engines. :-)

Colyn
Colyn Firth

This is not the forum for hot rods ..lol,lol, smiley etc!
Gary Lock

Back to the carbon thrust bearing------
How many horses are you expecting Dom.
I'm on 2300cc-with around 10psi(hopefully)yet to be run but expecting around 200+ ish
willy
I like thread drift
William Revit

Willy, i think you would expect a bit more than "thread drift" with your engine if it gives 200 bhp!

Sounds like your car will be a " drift' car, going everywhere sideways!

Im starting to see why you guys are looking at tougher release bearings

Colyn
Colyn Firth

This release bearing was destined for another car, not mine. Still waiting to hear back from B&G.
Dominic Clancy

I tried a roller bearing in my car - from AP as I use a B clutch - and it lasted less than 300km before failing completely. When I took it out again, there was so much slop that it was practically falling apart. That's why I decided to go with the hydraulic concentric route from Burton, as Colyn has. It t can handle a racing car, it will handle this engine too.





Dominic Clancy

Just to clarify,
I did buy a roller bearing but I didnt fit it because i didnt like the idea of grinding grooves onto the ends of the clutch release arms to make it fit.

I decided to stay with the carbon type and so far so good. About 8000 miles on it so far.

I did like the idea of the hydraulic-concentric clutch cylinder though when you mentioned it in an earlier post Dominic but that is as far as I have gone.

Im hoping you will keep us all updated about the concentric cylinder when you reach the installion stage.

Cheers
Colyn
Colyn Firth

A friend of mine modified his 67 Mustang and used a hydraulic throw out bearing. I am not sure if the "hydraulic concentric bearing" mentioned above is the same or not.
However when he attempted to bleed the bearing/unit they could not get the air out of it. When installed the unit was turned such that air was trapped. They had to pull the tramny and bleed the air from the unit then reinstall it.
I believe he said the install directions did not say to bleed it before installation. They were quite frustrated.

Just a FYI.
Ray Ammeter

Thanks for the tip
Dominic Clancy

here's a photo of the release bearing and cylinder

Dominic Clancy

Doesn't appear to be the same product.
My friends in place had two hydraulic lines connected at the three o'clock position as seen from the engine end.
Ray Ammeter

Ray - Was it one of these------
If it was, yes sometimes they can be a real pain to bleed- when you open the bleeder all you get is fresh line fluid and the air stays in the cyl.
I usually fill the cylinder up before refitting the gearbox, and then after fitting the box up to the car, pump the clutch up and hold the pedal down for 30secs or so and then slowly pull the pedal back up-this sucks any trapped air up into the supply line, then open the bleeder and slowly push the pedal right down and hold it down-close the bleeder and then slowly return the pedal--it works--


William Revit

Similar in that, your pic shows the hydraulic lines in the same location. But not an exact copy..
I don't how they bled the air, but I assume it would be done similar to your process.
Ray Ammeter

Dominic,
I think you solved a diagnostic question for me in your first post. When the car is cold and Iring back the A out of the garage, I hear a low squeal as I get rolling and let off of the clutch pedal. The sound happens only when the clutch pedal is being pressed and soon goes away after a bit of driving. I guess the carbon has come loose from the cast iron housing, right?

thanks,
Tyler
C.T. Irwin

Tyler
A noise like you describe can be from a dry spigot bush as well
willy
William Revit

Willy,
Isn't the spigot bush bronze? Does it need to be lubed?

Tyler
C.T. Irwin

Tyler
The bush is sintered bronze, which is porous
Most new ones come already oil impregnated but some don't and have to be soaked in oil for an hour or two before fitting
An old workshop trick if in a hurry to fit one is to stand the bush on it's end on the palm of your hand and fill the centre up with oil, then get the thumb of your other hand and push as hard as on the top end pressurizing the oil--after a few secs the oil can be seen weeping out through the wall of the bush--
Usually what happens is if the engine has been apart and say the crank has had a good wash down or been in a bath, the lubricant gets washed out of the bush- In this case a dob of grease up the hole does the trick

Another problem is that some supplier supply a straight, non sintered brass or bronze bush which won't hold lubricant--these aren't so good, and need a good dolop of grease in there to keep them lubed

Basically if you have the engine out and are reusing the same bush it needs grease whichever bush it is

willy
William Revit

Well, couldn't time it better if we tried
Today's job was to fit a new crank in a mate's A------which meant a new bush
Here are a few pics of pressure filling the sintered bush

1-bush as it came
2-filled with oil and pressure applied, you can see the oil starting to weep through
3-getting more oil soaked in
4-fully lubed and ready to fit

William Revit

2

William Revit

3

William Revit

Ready to go

William Revit

This is a carbon thrust bearing that failed in a friendís car (MGB) after less than 10,000 miles. Clutch was working fine then one day just grating noises and no clutch, engine out and found this. Thrust ring on pressure plate also ripped off.
Mike

Mike Ellsmore

There is someone in Oz who makes roller release bearings as an alternative to the carbon release bearing
Alan
Alan Anstead

This thread was discussed between 08/01/2018 and 04/02/2018

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