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MG MGB Technical - sealing my exhaust

I hopefully part qualify for joining in your thread as my MGA has a 3 bearing MGB engine installed and it it really transforms the car.

It also has a tubular extractor exhaust manifold (3 into 2 into 1) fitted which works really well.
But the lowest part where the 2 downpipes join into the Y section just keeps coming loose.

I have tried different clamps and sealers but this doesnt stay gas tight for long and I am kind of learning to live with the exhaust blowing through.

It must be due to engine movement but the engine mounts seem to be really solid.

Does anyone have any suggestions?

Colyn
Colyn Firth

Colyn,

Does the exhaust have the brace that is bolted to the point where the engine meets the gearbox?

Charley
C R Huff

Colyn-
If you're using the cast iron exhaust manifold, check to be sure that the conical sealing gasket is installed properly. Because the interior of the bottom of the exhaust manifold has a conical sealing surface, the exhaust manifold gasket should be installed with the conically-shaped end facing upwards into the conical recess of the exhaust manifold. The gasket is squeezed between the exhaust manifold and the triangular sealing flange of the exhaust pipe in order to achieve its seal. Note that the headpipe has a flange welded on it to allow the triangular sealing flange to compress the conical gasket when the machine bolts are tightened. If you use an old headpipe when you do a rebuild, then you will be running the risk that the welded-on sealing flange has significant rust damage and that it will eventually fail to the point that the machine bolts will pull down through the triangular mounting flanges. If you have an indication of an exhaust leak that you cannot find, some backfiring while decelerating down a hill, and maybe even a loud squeaking noise on rough roads, then you might want to check and see if your headpipe is starting to migrate downward toward the pavement.
Stephen Strange

Not certain about the brace Charley so I will have a look at the system over the weekend to check.

Thanks Steve, I will try to upload a picture which I think shows the fabricated steel tubular system better than me trying to describe it.
I think it is a Moss system.
It has the heat resisting wrap on it which I would prefer to replace by having it electro coated (as recommended in "the book" but it is about 4 years old now think it probably makes more sense to do this when I replace it.

Many thanks

Colyn

Colyn Firth

It has to be relative movement between the engine and car mounted sections, not surprising as its torque reaction that twists the engine on the mounts, and you put the MGB engine for more torque. IMHO worth a bit of effort as a good exhaust system transforms a car, making it so much more pleasant to drive. If the brace is there and it still pulls the system apart then maybe re-thinking the attachement to the car to let it move around more is the way to go?
Stan Best

Or another possible, you could find a flexi section that fits? A lot of FWD cars have these now, and the TF has one to allow for engine shunt with the stubby exhaust that car has.
Stan Best

If you want a more flexable mounting on the car you could modify the mountings to take modern rubber band type hangers.
David Witham

Thanks for your help everyone, I can see now that my attempts at sealing the exhaust at the 2 into 1 connection are only ever going to be a temporary fix.

I think I will first investigate the engine movement issue to see if I can reduce it. Im certain that the exhaust downpipe doesnt have a brace on it so that is another possible cure.

If I cant solve these, then the flexy connector is the probable answer.

Thanks all
Colyn
Colyn Firth

Colyn-
The pic you posted doesn't help a bit. Tip: the exhaust is on the bottom side!
You really need a brace or two from the exhaust to the engine/gbx; as it is, you have the car levering on the joint with a very long handle.
What manner of clamps are you using?

FRM
FR Millmore

Thanks for that FRM, I have often wondered where that smokey stuff went before it came out of that sooty tube at the back of the car!
You MGB guys have it easy, you can put your head under the bonnet and actually "SEE" where things go.

We MGA owners have to work by feel alone! Still got the burn scars to prove it!

I have the standard (Moss) flat exhaust clamps which have a captive bolt through the flanges.

I have just bought some slimmer stainless steel clamps with stronger high tensile bolts which I have been told will help but it means removing the exhaust to fit it and I have not yet got around to tackling the job.
To be honest, each time the weather is good enough so far to do the job, the temptation to go for a drive in it has just been too much!

Thanks again

Colyn
Colyn Firth

This might not be the advice you want but take it to a muffler specialist. Its money well spent and the job will be done right... Its fairly cheap and they know what they are doing.
JRB Mr

haha, not 'round here they don't!
Dave O'Neill 2

This thread was discussed between 01/04/2011 and 29/04/2011

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