Just a quick one really, I have an old fiat twin cam engine with worn manifold and header pipes that has been leaking exhaust gases since I have owned the car. I have replace the gasket in between the two offending items but the gases still escape, so should I;
A, get high temperature silicone and use that alone

Or

B, sandwich the gasket top and bottom with the silicone

Personally I am thinking of A, removing the gasket and just using the silicone

Any advice is much appreciated, I know I should replace both parts, but the header pipe is a bespoke part, and the minfold is worth more than a engine swap

Thanks again
Steppers

You can try and bodge it but in the end you need the manifold flange milled flat

I'm with snapper - you need the manifold machined flat and a new gasket.

Anything else will be a bodge and if it works will be very temporary before you're back to sort it again.

I know it will be a temporary fixed, but I have no money in the pot.

Plus I know that with my MS worsening I will be looking to save for an automatic conversion and it needs a new loom, the list goes on. So it will be a temporary fix. I just want to get the thing on the road, just to have a little bit of fun before the poo weather come

[Edited on 29/7/21 by steppers]

Is it a flatness issue or alignment?

Plumbaflue made a leak free joint on the slip joints on my pinto manifold and normal bathroom silicone has sealed up a few silencers I've made repackable.

I'd say give it a go. You have very little to lose. Don't use silicone if you have any lambda sensors in the system but otherwise, give it a shot.

It was leaking when I bought the car, so it has burnt out in a couple of spots both on the manifold and header pipe, so they aren't completely flat. The silicone that I have is expected to work up to 1200 degrees

I do appreciate all the advice given

Cheers
Steppers

Do you have, or know anyone with a largish belt sander? Use that to get the flanges flat.

Large sheet of glass, 80 grit sandpaper off a roll to the required length, a bit of spray adhesive & hey presto, your own flatbed milling machine, takes abit of elbow grease, but as long as you keep the manifold square on to it, it will take out the imperfections/misalignment unless it's huge.

If going the other route I wouldn't use HT silicon, I would use a thick exhaust paste like Gun Gum or similar - that would certainly give a temporary fix, again, unless the misalignment is huge

quote:

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Originally posted by russbost
Large sheet of glass, 80 grit sandpaper off a roll to the required length, a bit of spray adhesive & hey presto, your own flatbed milling machine, takes abit of elbow grease, but as long as you keep the manifold square on to it, it will take out the imperfections/misalignment unless it's huge.

^^Thats a good shout, it does work, and is good exercise.

If you go for silicone don't bother with expensive stuff, get the cheapest clear you can, so long as it's silicone and not acrylic. I've used it on quite a few manifold - downpipe joints and it has never burnt out, no one ever believes it though...

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nick205 - 3/8/21 at 01:13 PM

quote:

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Originally posted by russbost
Large sheet of glass, 80 grit sandpaper off a roll to the required length, a bit of spray adhesive & hey presto, your own flatbed milling machine, takes abit of elbow grease, but as long as you keep the manifold square on to it, it will take out the imperfections/misalignment unless it's huge.

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I've used this technique before(with finer grade sandpaper) to de-glaze bicycle disc brake pads with success. Make sure the backing surface is properly flat (glass works well). As "russbost" says keep the manifold sqaure on to the flat surface. If the surface needs a lot of work it may take some elbow grease/time, but it's a good and low cost solution.

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