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MG MGB GT V8 Factory Originals Technical - Header Leak

Hi

One of my headers leaks where it bolts to the head. I know this has been discussed before (often), but I've had a trawl through the archives and I don't think anyone has posted a solution.

I've had it off (?) and it doesn't fit. The hole in the header flange on cylinders 6 and 8 simply doesn't match up with the exhaust port in the head. There is an area along one side where gas can easily escape.

The only detrimental effect is an irritating ticking sound, but I've just spent ages rebuilding the motor and I'm not going to put up with a leaky exhaust.

Possible solutions seem to be:

1) Bend the pipes so that it fits.
2) Weld-up and re-grind the mismatched area.
3) Buy a new pair of headers.

1) Seems to be the right solution, but I don't know how to go about it.
2) Seems more feasible.
3) 200 quid.

So many people have commented on this problem, someone must have solved it??

Regards,

Nick



Nick Wilson

I have recently become aware that for a long time the tubular manifolds from a number of sources do not mate correctly with the ports in the head, but I have not heard of them being so far out as to leave a gap to the outside world. These manifolds do warp in use, making it impossible to refit (can't get the bolts in) unless one files out the holes. I can see that in time, with much filing, one could uncover the edge of the port. But are you sure the flanges are true? The last set I had were not, try laying a straight-edge across all four.

What gaskets are you using? I have seen three types - thick single metal-sandwich, thin dual-flange composition, and thin dual-flange metal. Only the thick single metal seem thick enough to cope with any 'non-trueness' of the flanges.

Clive Wheatley recently told me about the mis-match between flanges and heads, discovered when he had some blanks made and happened to offer one up to a head. He now has dual flanges, which may help reduce warping, but maybe the four flanges in a single billet would solve the warping and lack of true altogether. I have been thinking of cutting lengths of 1/4" square bar and welding them in between the flanges to force them back into position and hold them there.
Paul Hunt

Paul,

The flanges seem to be true (all in the same plane). It seems that the whole assembly has "shrunk". I had to file out the mounting holes a little to get it back on.

It seems to me that the fit is so poor that the small ammount of filing I did was enough to leave a gap along one side of the ports.

I am using thick-ish metal gaskets - one per port. (I assume the gaskets you describe as "dual flange" are for two exhaust ports each??)

I'm sure that you are right. If the four flanges were cut from a single piece of metal, the probem would be solved. That's well beyond my metal working abilities, though!

I was rather hoping someone would recommend an exhaust sealant, or something. I used some exhaust assembly paste but it it is very brittle when it hardens and flakes off immediately.

Cheers,

Nick




Nick Wilson

I think ou can get a one piece exhaust gasket, which covers all ports, one of my friends has a Land rover discovery and he was just used a one piece gasket, alot less work involved then trying to align each gasket individually.
Ian Sanders

Hi Nick,

I've also had the problem of leaky headers. I had to spend ages filing the flanges flat, when I first fitted them. Then when I hoiked the engine to replace the clutch I had nearly the exact same problem as you; I couldnt get the bolts in for cyls 2 or 7. I fixed it by filing the holes. Then, when I found that created a leak, by building up the flange with weld and then filing it flat. This seems to have worked pretty well so far. Paul's right they do warp in use, so just replacing them will mean that you'll get the same problem again. I thought that the warping was the internal stresses in the welds or the bent tubing in the manifolds relieving themselves during the heating/cooling cycle in use, and that once they've relaxed into their natural position they shouldn't warp any further (I hope!)

FWIW this was a really pleasing job to do. It only took a couple of hours and such a difference afterwards!

Happy filing

Phil

Philip Shingler

Phil,

I've been contemplating buying a MIG welder for a while. What sort do you have and would you recommend it?

Cheers,

Nick

Nick Wilson

Nick,

You could try high temp silicone gasket, but, as far as I know, only available in trade quantities - favoured amongst Hot Rodders.

Paul
Paul

Cheers Paul

Do you know the brand name? Hermetite makes a high temp. gasket sealant. I may give that a go but I don't think it's intended for filling gaps.

Nick


Nick Wilson

I had one set of manifolds off and back on again about three times, and had to file out the holes a bit more each time!
Paul Hunt

Hi Nick,

I've got an SIP Migmate 130 Turbo, as sold by B&Q. Cost about £130 from memory. Seems to work pretty well (I'm no artist but nothing's broken yet) my one bugbear with it is that the wire feed always shuts off after the power which means that i always end up trying to start the next weld with an inch of wire coming out of the nozzle. I clip it off with side cutters to make tidy welds but it's irritating.

Phil
Philip Shingler

I use a 100 Anp. unit. Works for most things but 120/130 Amps. would be that bit better. The difficult job is always welding thin metal though, at low currents. Only skill and experience count here - neither of which I have. One more tip; buy an angle grinder. MIGs and angle grinders go together like microwaves and frozen meals.

Ian Thomson.
ian thomson

Nick.

RTV Silicone sealant from Van Chem tel 01132715515 in Leeds but may only be available to Trade.

Paul
Paul

This thread was discussed between 29/04/2002 and 01/05/2002

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