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MG MGB GT V8 Factory Originals Technical - Exhaust manifold port alignment
|After some substandard work done on my car, the manifold gaskets on each side started blowing after only 200 miles. I had the manifolds refitted but examining the blown gaskets I notice from the carbon marks that they are clearly not matched to the exhaust ports. I would say that they are nearly 1/4" out on two sides. This means that there must a substantial restriction on the efficent escape of exhaust gases from the engineas the face of the manifold is overlapping the ports on the engine. |
I'd like to know what would be the effect of this on performance and overheating. I'd also like to know what can be done about it? Anyone know anybody in the S.E UK who could sort this out for me. I thnk that I need to get the ports matched or else buy another set of exhaust manifolds which have been made properly.
I have had a similar problem with my MGB hive RV8 manifolds. The holes in the flange are much too big and from looking at the gaskets they are mis aligned.
I have always had a ticking sound and at first thought it to be lifter related but now I am fairly sure it was due to mis alignment of the exhaust manifold flanges. I have removed the manifolds and run the mig welder around the inside where the flange hole was too big, then ground back using the gasket as a template.
Seems to have been no adverse effect apart from the ticking noise. No Overheating, with standard guage runs just below N. Performance is good but obviously there could be room for improvement. Hopefully I will be able to try it out this weekend.
I've always wondered what that ticking noise was, has it now gone?
|Are you using the single gaskets? Am I right in thinking these can be installed several ways of which only one is correct?|
I have seen three types of gasket: thick individual steel, thin green/grey composition pairs; and thin steel pairs. The first reduce the clearance between manifold and inner wing but otherwise are best, the second are crap as they break up, and the third are second best as they give reasonable sealing and better clearance.
Are you using tubular manifolds? IME experience these warp in use, have you put a straight-edge across all four flanges and looked for gaps across the faces of the flanges? I've had to put gasket compound on one edge of the outer gaskets to compensate for warpage.
The other warpage that occurs is that the pipes tend to move closer together, so even though they originally go on OK if you remove them they are a bugger to refit because the holes no longer line up. I have had to spend some time over-drilling and even filing out mine.
Exhaust ticking varies with throttle opening whereas other tickings usually do not. You may also be able to see carbon around the gasket edges, or feel blowing, or even smell fumes under hard acceleration.
Your last paragraph describes my symtoms exactly.
I'm not using a gasket compound - any recommendations - I gather a grey compound used in the aircraft industry is good.
|Marc, you could try Specialized Exhausts in Mitcham. I don't have a phone number but they're on an industrial estate near the train station. Make and fit exhausts and manifolds to spec, reasonable prices as well. Welded a hole in my exhaust for free!|
|Paul from Surrey - I just used a generic exhaust assembly paste (not repair paste) from Halfords, it is certainly improved the seal but I can still see traces of carbon on it.|
This thread was discussed between 02/07/2001 and 04/07/2001
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