XFlow Exhaust Manifold Gasket......Again!!!

[virden]

Have just blown my 3rd gasket between my 4:1 and the head at no.2&3 cylinders, in just 3000 miles. The gasket always blows at the top and in the same place. I have tried putting Halford's exhaust mastic over the break, but it does not hold.

 

I have been given two possoble causes: 1, the lack of a forward bracket means the weight of the silencer is pulling the manifold away from the head. Or 2, that the faces of the manifold and head are not true and have to be ground square.

 

Any suggestions? And how do I go about getting the surrfaces ground? I don't want to take the head off if I can help it.

 

1700 Super Sprint, Team Lotus and clams

[puremalt]

Certailnly doesn't sound right. I think your explanation of being out of true is the more likely. My 4-1 exhasst doesn't have support but has only blown the same gasket once in some 20000 miles. Take it off and clean it up with emery cloth (the manifold too) and try the Seven workshops copper gaskets- they are very forgiving. There could just be crud on either surface.

 

Windscreens... They're for poofs

[John Ryan]

I had the same issues. Soved by using some specially made copper gaskets (I think they may be by 7 workshop?), that cost a fortune, but do actually work.

 

 

[pete east]

The trick is to tighten the manifold bolts a second time, after new manifold gaskets have been fitted, but when the engine is HOT.

My gaskets used to let go after a just a few thousand miles, until I started doing the above,

What is surprising is that you can get the bolts as tight as you like, when the engine is cold, but run the engine until it is hot, and then you will find that you can easily get several more turns out of them when the engine is at working temp.

If the bolts are not tightened in this way, exhaust gas can start to get past the gaskets when the engine is hot, and once that happens, they are stuffed.

[pete east]

Ps Although expensive the copper gaskets sold by 7 workshop are a good idea, because copper expands faster than steel, when heated, this will have the effect of increasing the pressure of the gasket against the mating surfaces of the head and manifold, but ie would still advocate re tighteneing the manifold bolts once the engine is hot, because replacing the copper gaskets every few thousand miles would be a bit expensive.

[Gordon C]

I use a gasket from Vulcan Engineering. Laminated, not cheap but work a very very well

 

_________________________

 

Gordon.......joint Surrey AR

 

 

[Clousta]

I had the same problem. John at Redline Components solved it by ensuring that the faces of the manifold were flat. He used a good old fashioned bastard file and quite a lot of elbow grease, but not a grinder. I can't recall if he tightened the nuts again when hot.

 

The original builder had used studs and coper nuts to secure the manifold. With this set up one has to dismantle the manifold and part of the exhaust to remove it from the studs due to their length. These were replaced by cap head bolts which will make exhaust manifold gasket changes simpler in the future.

 

Gavin

1988 1700 Supersprint (LA, long cockpit)

[pete east]

I use cap head bolts for the exhaust manifold/s on my crossflow, and it `may' be that when they are hot, they increase in length slightly, allowing exhaust gas to creep past the gaskets.

Since I started tightening them a second time when hot, (after fitting new manifold gaskets), I have not had to replace manifold gaskets at all, except when taking the engine out, or cylinder head off, and my gaskets are the standard CC items, not the expensive copper type.

Be interesting if people did check their manifold bolts, when the engine is hot, a bolt that simply could not be tightened any more without destroying it, when the engine is cold, will usually give a half to two turns more when it is hot.

Taking them off does`nt seem to be a problem either, I just give them a dose of WD a day or so before I take them out, and they turn out easily..

[Bricol]

My old Westie used to have a xflow - I used to re-use standard Payen gaskets on a Chamberlain maniold (might have had to open the bore slightly to match the manifold) with no hassle at all. But you had to tighten all bolt loosely, then nip the ones up where the manifold flange was furthest from the head - no2 and 3 - get that tight, then pull up the outer pipes.

 

Never tightened them hot as I wanted to be able to undo them again.

 

Bri

[pete east]

Like I said. a small dose of WD the day before I wanted to take the bolts out, and every single one comes out smoothly and easily, no problem, and no constant replacing of gaskets.

[rgrigsby]

The 7 Workshop copper gaskets definetly help but you need to be sure the head and exhaust are flat as well.

 

Rob G

 

[andy couchman]

Another vote for the Vulcan solution. Not cheap but I was fed up with having to replace various other alternatives. Check out theior website for costs etc.

 

Andy

[Graham Sewell]

Agree with Rob G - that is how Chris Wheeler fixed my blowing exhaust.

 

Cheers,

 

Graham

------

Low tech luddite - xflow and proud!

[virden]

Guys, thanks for your help.

Re the "7 workshop" the only one i can find on line is for Austin Sevens. Are we talking about the same people?

[Clousta]

7 Workshop

 

Please let me know if they have the copper exhaust gaskets in stock. I have been waiting for ages.

 

Gavin

1988 1700 Supersprint (LA, long cockpit)

[Terry Field]

I have always used copper gaskets with great success, but remember not to let the exhaust 'hang' on the studs while you are tightening the nuts. Support the exhaust so that it remains as parallel as possible to the block and you will avoid damaging the gaskets during the installation.

 

Terry

[Nigel Fox]

I would think this is your problem;

"that the faces of the manifold and head are not true and have to be ground square."

It is unlikely the problem is with the head. Fit the manifold without a gasket and bolt up, then check for gaps between the manifold faces and the head using feeler gauges. It is likely you have a gap at the point of failure.

Remove the manifold and file/machine the faces, until you have a fit. It may be you have to remove metal from the opposite side of your failure point, or even from cylinders 1 or 4. Once you have a snug fit the gasket should nip evenly, gasket type may then not be too much of an issue..

 

 

 

Full time class 4 Zetec

[andy couchman]

Not entirely convinced about flat surfaces only being the issue...

 

The main problem seems to be the 'double' manifold for cylinders 2 and 3 (rarely had a problem with 1 or 4). You have the weight of the manifold plus silencer bearing on the gasket. The silencer is relatively firmly fixed (rubber mounted) but the engine will move about and so try to flex the weight of the sytem against the rubber silencer mounting.

 

The manifold is held on by two bolts only and they are at the sides rather than on top and bottom.

 

The standard multi-layer gasket seems to have some 'give' in it and, in my experience can blow out the inner material, presumably because of the rocking motion being imparted on it.

 

I guess that what we may be saying is that a 'solid' gasket (copper or Vulcan thicker ali material) is the way to go, not least becxause it has no 'inner' material that can be blown out. Does that make sense?

 

Andy

[puremalt]

Perfect sense, nicely put

 

Windscreens... They're for poofs

[virden]

Thanks guys, lots to go on.

I seem to recall from other threads that my chassis (An Arch 1996 S3) may have hidden under the skin, a threaded hole in the lower rail to allow the fitting of a forward bracket to support the silencer. Anybody know where this is located. I don't want to go making bradle holes on spec!