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MG MGB Technical - Knocking Tubular Stainless Manifold

Hi everyone,

My Dad's got a '69 MGB, and he's fitted a stainless steel tubular manifold to it. Under load, it's knocking - presumably against the rest of the chassis/body.
Has anyone had this problem? Is there any way to fix it? I'd like to sort it for his christmas present (if it needs a bit of work, I should be alright - we've just spent a year bringing my midget back to life, so I'm alright with tools and the rest).

One idea I was given was to wrap the manifold and down pipe (excluding joints) to absorb the knocking, but it feels like a bit of a bodge to me...?

Any help really very much appreciated!

Josh Spooner

If it is knocking the chassis rail then wrapping it is going to put more stress on the manifold as it won't be able to move so far, but the engine will still be trying to move it as much as before. Wrapping is also going to wear through very quickly under those conditions. Which brings me on to the question of the condition of the engine mount rubbers, are these allowing the engine to rock more than it should? Or positioning the engine incorrectly? There are usually one or more spacer plates between the mount and the chassis bracket to take up dimensional variations. If these are on the alternator side you could try moving them to the carb side, which should move the engine over a little bit.

But exhausts are a pretty variable thing, many people have difficulty getting a perfect fit these days. You may need to have a look at how much clearance there is between pipe and engine, and put a kink in it to take more of this up.
PaulH Solihull

The first time I fitted a 3 branch tubular manifold to a B, I exchanged it 3 times, they were all different and didn't fit!!!In the end I gave up and did some heating and bending. I've fitted 2 more since then and have had to "modify" both of them!!
Clamp the flange down accurately and securely before attempting to bend though.
Allan Reeling

Most unfortunate. The first and only 3 branch tubular exhaust manifold I fitted onto the GT was a perfect fit. I was, in the beginning as you are now, suspicious, as it had come from an unknown source. The measurements were all pukka, so in it went. But to the point; Modification and welding skilss would be a great benefit. Have a look at some of the You tube contributions under 'how to make your own exhaust systems'. There are some skillful fellows out there! Mike
J.M. Doust

To add to my last comment. At present it seems that the Peco system is the best both in fit, and performance. As Stephen says in 'The book'. It is one of the few systems that takes into account the siamesed exhaust port thus the middle tube is close to double the volume of the other single ports. Ie is properly tuned. If you select the correct one( standard and big bore variant.) it eliminates the middle box so is easy to fit. Sounds good at low revs, and is actually quiet at cruising. All round excellent system. Mike
J.M. Doust

This thread was discussed between 13/12/2011 and 16/12/2011

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