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Dave Herrod

exhaust manifold sealant

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I am fitting a second hand mild steel exhaust manifold to my 4-cylinder engine. The manifold is, I believe, triumph tune (or a very very close copy) as sold by Moss. On inspection, the wall thickness around a couple of the ports looks somewhat minimal and I wondered how best to improve my chances of getting a good seal. I have noticed references in posts to not fitting the gaskets dry, but no views on what best to use in way of sealant.

 

All thoughts gratefully received.

 

Dave.

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Hi Dave

 

You could use an exhaust sealing paste such as Holts Firegum which should be available from somewhere like Halfords.

 

It is a white paste, probably ceramic based, which hardens with heat. I used to use it on A Series exhaust manifold clamps all the time and it worked well.

 

You might be best to run a good file evenly across the faces of the exhaust manifold ports to ensure they are flat first. I take it you are using a gasket?

 

I didn't use any gasket on a 2.0 Litre Ford Pinto race engine, just made sure the mating surfaces were flat, and never had a problem, unlike a slight leak on the inlet side.

 

Regards

 

Kevin

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Revington can supply thicker manifold gaskets (113122-1) for this sort of job.

 

In my experience, the Triumphtune exhaust manifold may not be constructed very well. I tried a number and found that the manifold had to be expanded to reach the first and last manifold studs. In so doing, the tubing twisted such that the faces no longer sat flat. I spent one and a half days grinding the faces until they sat flat on a solid, flat piece of solid timber, checking with feeler gauges until I was satisfied that I would get a gas-tight seal. Patience is a virtue, it has survived 12 years!

 

Ian Cornish

Edited by ianc

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I appreciate that the thread is a little old, but I find silicone an excellent exhaust sealer. Never hardens so exhaust is always dismantleable (if such a word exists) without a hammer – I hate the hardening pastes.


High temp silicone such as https://www.screwfix.com/p/mapei-mapeflex-firestop-1200-c-high-temperature-grout-grey-300ml/25153 is good for 1200’C and suitable for other sealing tasks about the car.



Alan

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I appreciate that the thread is a little old, but I find silicone an excellent exhaust sealer. Never hardens so exhaust is always dismantleable (if such a word exists) without a hammer – I hate the hardening pastes.

High temp silicone such as https://www.screwfix.com/p/mapei-mapeflex-firestop-1200-c-high-temperature-grout-grey-300ml/25153 is good for 1200’C and suitable for other sealing tasks about the car.

 

Alan

 

 

I was looking for something similar that would stay flexible earlier in the year, but gave up as I couldn't find anything that didn't harden at exhaust temps. So was interested in the link and it sounds good, however a lot of the review seem to indicate that this does also harden and crack.

 

" Having read the product spec I thought this would be perfect for sealing up around the register plate of my stove and some joints around the cement board surround. I have however found it does go brittle and fall out of the joints after just one hot burn. Perfect if your stove is an ornament, worthless otherwise. "

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Even the highest temperature silicone gives up about 300ºC. 1,200ºC is dreamworld.

 

Wideband O2 sensors suffer from silicone poisoning too.......

 

I like the Bosal exhaust paste - it's fireclay though and not flexible. Trick is, to make the flexing happen somewhere else - put a flexy section in somewhere. Present on nearly all modern exhaust systems in some form though mainly for NVH reasons.

 

Nick

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Hi Nick

 

I think the ambition given not perfect alignment of faces and tendency even when clamped for movement to occur and then the odd blow to develop is to find a magical compound that will flex with the movement and not set rock solid at high exhaust temps. It may exist but I have never found it. It did find some Silicon Sealant that was rated at 700C and thought it might be good enough to seal frayed wrap, and fill a few holes in the wrap, left the engine idling not long after first start up, fortunately out of the garage and with the bonnet open, returned after 5 mins to find flames rising from the manifold wrap as the silicon gave of gasses and ignited, fortunately extinguisher to hand and no damage (the wrap doesn't burn).

 

The best solution to the exhaust manifold problem I have found so far is apply lots of heavy moly grease to the gasket, and keep checking the clamp bolts, I would find even during and event that they would take and extra 1/8 - 1/4 turn.

 

Alan

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Dave

 

As well as using RevingtonTR improved manifold gasket, I think they also recommend 'Heldite' sealing compound when fitting the gasket. It will seal against steam and gases so must be resistant to high temperatures and doesn't go hard.

 

Rob

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Thanks all for the replies.

 

I have never used sealant in the past, but suspect that the standard manifold is a little more forgiving than a tubular one. I think I will try with the standard gasket that I have, perhaps with a graphite or copper grease. If I have a problem I will try something else.

 

Interesting thought about ensuring greater flexibility elsewhere.

 

Dave.

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The simple answer to leaking manifolds has always been to insert a length of flexible pipe, usually immediately after the confluence of long primaries (as in tubular manifold), or after the downpipe fitted to short primaries (as in cast manifold).

 

The important factor is to get this flexible section fairly well forward, as in forward of any exhaust mount to the rear of the bell housing . . . . assuming we're talking of a conventional RWD set-up as opposed to a transverse engine. This way the manifold and/or downpipe are free to move with the engine, and pretty much insulated from whatever movement might be caused to the remainder of the exhaust system by the vehicle's motion.

 

The choice of flexi pipe is endless . . . . and not expensive . . . .

 

see ebay link, for example . . . . https://www.ebay.co.uk/sch/i.html?_from=R40&_trksid=p2380057.m570.l1313.TR9.TRC2.A0.H0.Xflexible+exhaust.TRS0&_nkw=flexible+exhaust&_sacat=0

 

Cheers

 

Alec

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Hi Alec,

Good thought.

The standard exhaust (in mild steel) does not have an expansion joint.

I can imagine converting the exhaust to SS contributes to the issues of leaking gaskets.

A mild steel system expands at 1.2 mm/m/100 degrees C, so at say 400 degr. C will expand 4.8 mm/m.

An austenitic SS (like 304) will expand at 1.8 mm/m /100 degrees C so at 400C this equals 7.2 mm.

This will put quite a bit of force on the systems fixed points. The exhaust manifold is one of them.

Regards,

Waldi

Edited by Waldi

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I have a mild steel SAH/TriumphTune 4-branch manifold bought in the days when they were built to a higher standard than would appear nowadays and have had no leakage problems (hope that doesn't jinx it). Just over a year ago, I replaced the ancient Falcon stainless steel exhaust system (rattling baffles finally got to me!) with a single box TriumphTune system with standard (rigid) fittings and so far, so good.

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Hi J'all

Use high temp silicone - orange stuff: use it on my race engine

The head and the manifold - especially the thick bit to which the tubes are attached never get that hot because of the heat sink effect of the head

Just get the manifold as flat as possible coat both sides with high temp silicone and let it go off for 15 mins then bolt it up

If you want pressure resistance then use Wurth motor sealant but it is not generally necessary

Michael Hunter

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