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MG MGA - exhaust pipe mounting

How much clearance is there between the exhaust pipe and the rear axle? When I try to install the exhaust pipe, it hits the rear axle and I can't quite get the long bolt thru the intermediate hanger. Maybe the hanger from the frame is a bit too short (a repro piece, or the bracket on the exhaust pipe is a bit too short. Or maybe because I'm working on a bare chassis with no body/engine/trans weight the frame is just sitting a little high relative to the rear axle....

George
G Goeppner

George

I think mine is pretty standard. The pipe runs more or less parallel with the underside of the floor with about 3/4" gap, passing about 2" under the rear axle to the box which starts 4" behind the axle just behind the handbrake lateral cable.

Steve
Steve Gyles

Without any weight on my exhaust was also interfering with the rear axle. The axle restraining straps were further from their mountings than the exhaust needed to go, so I figure there will be no problems once it's all back together.
N McGurk

I hung my exhaust with the rear axle hanging from the rebound straps so I would be sure to clear if I launched off a large bump. I don't know what brand of exhaust you're fitting, but I installed a maniflow single box system and I had to do a lot of fussing to get it to fit correctly. In fact it in no way matched the old Falcon exhaust that I pulled off. So I guess also make sure they sent you a correct pipe.
Mark J Michalak

George
When I rebuilt mine I had the springs retempered. Bob West organised this for me, so I expected it to be correct. Even with the body on I could not get the bump straps on or stop the exhaust from hitting the axle until I had put a couple of bags of sand in the trunk and run for a few hundred miles. It soon sorted itself out though and everything looks OK now.
John Francis

The handbrake cable does commonly touch the exhaust pipe with full axle drop, and no problem as the cable will flex easily (as long as it doesn't flex much).

The rebound straps should keep the axle from hitting the pipe. If the axle hits the pipe, either the pipe is formed wrong or the rebound straps are too long or stretch too much (defective). Axle hitting the pipe on full rebound (car air born or in hard turn body roll) is a recipe for broken exhaust hangers.

For a current reference, I just jacked up my MGA, put it on stands, let the axle drop to pull the rebound straps taught, and took some pictures. See attached picture. With axle at full drop it does not hit the exhaust pipe (and never has).

These rebound straps are Moss Motors 1978 issue, in service since late 1986 with 245,000 miles accrued. Perhaps they made the parts better 30 years ago. I measured both straps to be sure, They are exactly 9-inches long after 25 years in service (and tight as a banjo string under load). I think they are supposed to be more like 8-1/2 inches long when new (but I don't have the exact design dimension).

The exhaust system is Moss Motors 2008 issue Falcon stainless system, a replacement for an identical system installed in 1986. I recon the parts are formed exactly the same, and the pipe is correct shape. At full drop I can stick my hand in between the exhaust pipe and axle housing, almost one inch of space there. The pipe hangers are original style in good condition (as always).

So if your rear axle is touching the exhaust pipe, I suggest you fix it. Start by measuring length of the rebound straps. If the rebound straps are no more than 9 inches long under load, and you have original style exhaust hangers, then the exhaust pipe must be the wrong shape.


Barney Gaylord

This thread was discussed between 13/07/2012 and 15/07/2012

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