Exhaust to manifold connection 1098cc

[MGFmad]

I am going to refit this soon and remember from my Mini days that is was a bit of a pain to seal the joint properly.

Any tips for doing this?

[bmcecosse]

Make sure the manifold is perfectly clean and smooth on the 'bell end' - and the exhaust flange is in good order - no splits or bent-over bits! Clamp must be good too - and bolts/nuts(should be brass) running easily on the threads. Offer up the exhaust and secure it loosley rear and middle - then put a bottle jack under the front pipe and ease it up into place on the manifold. Slight smear of exhaust paste sometimes helps - then fit the clamp and tighten (but don't overtighten!) the nuts. Don't forget to fit the little bracket that takes the throttle return spring. Then tighten up the rear and middle - and it should be fine !

[mike.perry]

Shouldn't need sealing if the end of the exhaust pipe flare is OK and you have a good clamp. Support the front end of the exhaust pipe on a sissor jack and wind it up until you have a good seal onto the manifold. Fit the clamp and tighten the bolts. Job done.

[Peetee]

Make sure the manifold is perfectly clean and smooth

Too right. And inspect it very carefully. Sometimes a layer of discoloured exhaust paste can look remarkably like the manifold casting.

[dunketh]

Contrary to what everyone usually says I found the one piece clamps worked better on my exhaust.
They have more flat area either side of the V which holds the pipe and manifold more securely.
The 'heavy-duty' two piece clamps allow too much movement between the pipe and manifold imo. At least on my system they did.

Also, use a proper assembly paste. The usual 'Firgeum/GunGum/etc..stuff from Halfords is rubbish and plainly wont seal for more than 6 months. I used hemetite red on mine, bought from the exhaust supplier.

[alex_holden]

The heavy duty two-bolt clamps made from thick cast steel seem a lot better than the standard two-bolt clamps made from pressed sheet that seem to distort the first time you tighten them. In my experience Firegum works if the manifold to downpipe joint is virtually perfect. If there is a large gap at any point (eg. because the flange is kinked) or the clamp allows it to move, the cement will soon crack and fall out.

[dunketh]

The rouble is, virtually all manifolds are going to be a bit pitted or rough and none of the cheap exhausts are any good.
The profile to the 'bell' bit tends to change depending on the weather and what the supplier/fabricator ate for breakfast that morning.

Best bet is to sell a kidney and buy a complete stainless system.

[alex_holden]

Cement will cope with a bit of roughness if you wire brush off any loose rust/old cement. It's possible to beat the downpipe flange close enough to eliminate any gaps with a hammer and dolly and enough patience.

[bmcecosse]

Used to be able to buy a short 'flexi' repair section for Mini exhaust - which can be used (with or without flexi - your choice) to repair an otherwise good Minor exhaust wherte the bell-mouth has taken a beating.

[superchargedfool]

as a mechanic I would state that any exhaust joint that is intended to give a degree of movement should not be assembld with a paste that will set hard.

[minor_hickup]

The heavy duty two-bolt clamps made from thick cast steel seem a lot better than the standard two-bolt clamps made from pressed sheet that seem to distort the first time you tighten them. In my experience Firegum works if the manifold to downpipe joint is virtually perfect. If there is a large gap at any point (eg. because the flange is kinked) or the clamp allows it to move, the cement will soon crack and fall out.

The old 2 piece cast clamps are superb, a much better designed item, however they're a bit thin on the ground now. I've sold a used item second hand for £20.

[bmcecosse]

The exhaust joint is not intended to give ANY movement! The pipe should be solidly clamped to the manifold! The whole exhaust system rocks with the engine - hence the need for good engine mounts and the steady bar to be intact, and some flexibility in the middle and rear exhaust hanger straps.

[alex_holden]

The old 2 piece cast clamps are superb, a much better designed item, however they're a bit thin on the ground now. I've sold a used item second hand for £20.

A supplier at the National was selling them for a lot less than that. Unfortunately I can't remember what they were called - it wasn't one I'd bought from before.