Trouble sealing middle exhaust, kent....

[milesinfront]

The bolt pattern of the kent exhaust was obviously designed for the solid cast iron manifold. As a result I'm having difficulty sealing ports 2&3 on my tubular system.

The leaks are always from the top and bottom of the flange. Only having 2 mounting points, left and right of the ports allows the flange to rock up and down i guess....

Any wisdom out there? Am I all alone with this one?

[Alan Raine]

We had this problem when I raced FF1600 in the 80's and early 90's. Because the 2 bolts are holding 2 pipes we had sealing issues and also had regular cracks around the flange. We used exhaust jointing compound to help stick the flange to the gaskets/head but that's not always good for exhaust flow. We also cut the 2 & 3 exhaust pipes and loosely joined them before the 4 pipes met the silencer. This relieved the strain on 2 & 3 but again may have disturbed flow and also changed the dB level

[youngoldy]

This is usually the norm, particularly on older exhaust systems.

One way I got around this, is if you put a metal ruler against the two mounting bores of the flange, and you can see daylight between the centre of the flange, then put the manifold pipes in a vice, and with a high quality metal file, flatten the flange, and keep checking how flat is against the ruler. Once you have a flat flange, ensure you use the correct gasket, and make sure you use the correct torque setting for the manifold bolts.

A reason that the flange might have been mis-shaped, is if the flange is not thick enough, or in the past, the bolts have been over tightened, damaging the gasket, not necessarily the threads!

An extra way to help prevent a leaking manifold, would be to use exhaust cement. Incredibly ugly, but if you haven’t got all the £££ for a new exhaust system, its a cheap way out.

TTFN

[Jacal]

The Australian regs don't require you to run the gasket. simply use high temp silicone sealant. Most of the guys in NSW were doing this when I started 10 years ago. The Red RTV for about $15 a tube Must be the high temp stuff it's easier to remove. As a bonus it's cheaper and much less messy than the exhaust manifold cement and doesn't reallly require changing any more often.

[milesinfront]

Thanks! I'll investigate both solutions...

[Tailgate]

I had the same issue with an aftermarket, 6 branch manifold I bought for my classic road car, obviously distorted during welding. I managed to find a machine shop who were willing to skim it, they did a good job and weren't too expensive, it must have been a pain to clamp it tight enough for machining but they managed.

Worth considering...

[milesinfront]

I used this stuff on the exhaust:- http://www.permatex.com/products/aut...sket_maker.htm

Lasted today's dyno test:- http://www.youtube.com/watch?v=yWy1r...layer_embedded

Any better goo out there? Will see how it goes... Thanks!