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MG MGA - Rear crank seal
|Does anyone have a seal kit for the rear of an MGA crank??|
|The MGA does not have an oil seal at the rear of the crankshaft. It has a scroll pattern machined on the crankshaft that throws the oil from the crankshaft (in theory!).|
To fit a seal considerable modification needs to be carried out.
See Barney Gaylord's website:
|I had a couple questions about the rear scroll. When it reaches a point that it is no longer effective in keeping oil in the block, can it be re-machined to work "properly"?|
That being said, I thought I read something about how most rear scroll oil leaks can be caused by a worn engine bulding up internal pressure and forcing the oil out.
When the engine is apart, how do you check the tolerances on the rear scroll?
|Mark J Michalak|
|It is not clear what you mean by "the scroll reaches a point that it is no longer effective". The scroll does not wear, it does not contact anything.|
A build up of pressure in the crankcase would force more oil out the past the rear main bearing. The scroll action could not cope with the increase. If there is a pressure build up, a check of the draft tube should firstly be carried out, and possibly replacement of the piston rings and maybe even a cylinder rebore.
The tolerances are given in Service Memorandum MG212. It also describes a rear main bearing cap modification if your engine number is prior to 40106.
MG212 page 1 attached (page 2 to follow).
|Service Memorandum MG212 page 2 attached.|
|A guy in our club has just fitted the rear crankshaft seal as described on Barney's site to his Twin Cam motor. After a couple of initial fitting issues he has it running perfectly - he added a backing flange to the modified seal to give it more rigidty. If I hear of any issues as time goes on I will post here - at the moment - zero leaks from rear of crankshaft.|
Why did your friend carry out the rear seal modification on his Twin Cam? Unlike the pushrod engine, the Twin cam does have a rear crankshaft oil seal as standard.
|I'm Pretty sure I just saw a new "Kit" being offered by Moss to retrofit a seal in one of there addvertisement mailers. It is similar to the one referenced in Barney's site. I believe it was around $300 however, this one did not require any machine work. I will try to find were I saw it and re-post.|
I'd be very interested in this seal as i am just trying to stop my TC from leaking badly at this point, (well, a large leak from the bellhousing giggle pin)having just rebuilt the engine. The original seal (fibre ring)was too tight and locked up the crank long before the rear cap was pulled up. I fitted a graphite rope seal arrangement which has failed miserably. I also have the drain holes in the rear cap. At this point in time i am going to pull the gearbox, remove the clutch and flywheel, and think.......
The TC seal has to be cut to get it over the crankshaft flywheel flange i.e. there is not a conventional seal with a lip and spring. I could not get this seal to work (ref above).
I was going to get a collar turned up and fit a conventional seal similar to Barney's mod (Terry Drinkwater tried Barney's mod but he advises that this didn't fully work.) and did wonder if the metal retainer was sufficiently strong enough, so i was thinking of something wider and thicker. Did your pal take any photo's or does he have further info?
|Don't discount that the oil is not leaking from your gearbox. I found out the hard way and re-assembled mine only to find out the front (1 dollar) seal was never replaced resulting in the gearbox leaking. Either add dye or if your gearbox oil is clean and your motor oil is a litttle dirrty you can sometimes tell thatway.|
He is a bit of a perfectionist and after he had trouble with oil getting on the clutch at a Sprint meeting he decided to go the whole hog - some people say the TC rope seal (2 piece) is enough, others disagree. There are now 2 TCs here in Victoria with lip seals!
He did not take a photo (silly fellow) but when I see him next I will get him to describe and I will post details.
|Thanks for all the comments guys. Barnys' mods look |
similar to what I was thinking.
Oil leaks at the rear of early BMC engines has always been a problem. The Moss kit for XPAG engines works well if the cap is machined flat & the lower half of the new seal carrier is bolted to the cap - have done this on 5 motors with no problems. I have also made a conversion for the 1275 midget engine.
The MGA and other 3 brg engines have the problem of a narrow flange on the crank. Ihave thought of welding a 1/8 thick ring to the crank flange that would cover the bolt heads & then fitting a speedi sleeve. Howerver there is little room between the bolts on the back plate to get a seal in.
Contacted Moss (US)and they are not aware of any seal mod either in development or for sale. Can you enlighten?
For what it's worth
In Brown & Gammons catologue they say'If the main bearings have worn....then the crank scroll can have touched and worn the housing. We have a method for building up and re-machining the housing providing the crank is not badly worn'
|Hi Guys, Yes the crank touching the cap is the problem. Who-ever ground the crank last time didn't set it up properly & the crank scroll is running .005" out. Cosequently the crank & cap are worn. The bottom of the cap has gone blue!.|
Since my last entry I have done as I was thinking. The crank has been modified, the back plate bored & the cap worked on. I have yet to assemble it all & test the work done but don't expect any problems
|When I got my replacement engine a few years ago from Lawrenz (www.lawrenz.de) he told me there was a teflon seal at the crank, but I have never had it apart to inspect. Doesn't leak any oil there.|
If you want more information, get in touch with him.
|When investigating opyions on how to fit a seal I came up with 2 options. Fit a seal in the back plate to run on the flange or modify the scroll area and fit the seals used on the 308 holden V8 - probably the same as the Chev.V8. I chose the former because the motor had not long ago been rebuilt so I didn't want to strip it right down. Fitting the 308 seal would have involved metal spraying the scroll area and completely stripping the motor to machine the block to take the 2 piece seal. If I was doing it again on a complete rebuild I would certainly fit the 308 seals. The only down side is that the crank has to be removed or at least lowered to replace the seal, where-as with the seal in the back plate it could be done by only removing the flywheel. Also with the 308 seal any replacement crank would have to be metal sprayed & ground but on the plus side the surface speed on the seal is much lower and guaranteed to never run dry.|
This thread was discussed between 28/03/2008 and 05/04/2008
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