Exhaust Manifold Gaskets

[SLB]

I've had similar issues on a 420 SEAC I used to have. I used the same gaskets as you and again a good hand tight not knowing the correct torque. I had one thread fail on me doing this and a helicoil had to be put in when the engine came out partly for other work. I think the thread had been damaged by a previous owner as all the others were completely fine.

What I found was that the bar joining the two halves was springy enough to allow removal of one gasket at a time but the heat generated seemed to affect the gasket and the torque the bolts were tightened to. I recall having to nip them up a couple of times after initial installation but once done had no more issues even after several years. I would suggest you try cleaning the faces with some fine wet and dry before fitting a new gasket and give it another go.

[mk1fan]

Tighten the bolts more with a bit of control - ie not like some ape with a four-foot bar. See if that closes it off. 'Hand tight' to me means not tight at all so while the split / spring washers maybe flat (which doesn't take a lot of pressure / force) but that doesn't mean the element is bolted down.

That said, they don't need to be that tight.

You could try a thin bead of high temp, snsor safe, copper RTV like V-Tech - https://www.vitaltechnical.com/product/rtv-gasket-... or Permatex - https://www.permatex.com/products/oreilly/permatex... which is used on the Speed 6 engines to form the manifold gasket.

So like a bead similar to 1mm2 copper wire.

[indigochim]

I had trouble getting some Peninsula manifolds I bought 2nd hand one here to seal. One the 3rd time of having them off I tried them on a straight edge and saw one end was a coupe of mm off the work bench when the other side was flat. I had them linished flat and by by issue. That was on my Chimaera but I guess you may have the same issue.

[Avroflyer]

Thanks for all the tips, PHers.
I've decided to dismantle, clean up the faces as best I can, use two gaskets at each port on the left bank and sandwich a thin bead of Permatek RTV in between each gasket pair. A bit nervous about 16 ft lb as the torque setting - seems a bit high to me, but what do others think?
I'd like to avoid having to take off the manifold if at all possible to not have to split the first joint along the exhaust pipe on that side!
Cheers
John

[SLB]

Best of luck! I've removed the manifolds maybe half a dozen times on a SEAC and a 350i and both were fine on the near side but the starter is an issue on the offside. On the first occasion I removed the starter but after that used a jack to press the manifold between the starter and the chassis - it's so close it just needs a bit of persuasion. I'd prefer not to tamper with the manifold to exhaust seals as the first time they disintegrated and I spent ages trying to find seals which would fit which I think were Jaguar in the end. Don't use exhaust rap as brand new SS manifolds lasted 1k miles on a SEAC - you could see them glowing red hot at idle after a run and they just disintegrated.

I did try double gaskets at one stage but they didn't last. I think if it's right it works. The best thing is to clean them as best you can both sides either on or off the car and use some of the RTV as has been suggested. I think that torque setting is about right.

[Avroflyer]

Thanks SAB but not sure what you mean by "exhaust rap" and what was it that disintegrated?

Also I'm still concerned about the apparent bowing of the attachment flange on the left hand rear position as in the photo above. Has anyone ever seen this?

Cheers
HERB

Edited by Avroflyer on Wednesday 26th June 08:40

[indigochim]

Avroflyer said:

Thanks SAB but not sure what you mean by "exhaust rap" and what was it that disintegrated?

They're on about exhaust wrap I presume as you see on many race cars or motorbikes. I believe it can cause the manifold to rust prematurely so presumable they mean the manifolds disintegrated.

Avroflyer said:

Also I'm still concerned about the apparent bowing of the attachment flange on the left hand rear position as in the photo above. Has anyone ever seen this?

As my post above it's entirely possible that the face plate is warped. My TVR guy got a mate to sort it for some beer money.

[mk1fan]

You could cut the joining peice of metal between the the two ports - like the gasket. Other than for fabrication alignment, I am unaware it serves any function once installed to the engine.

Assuming the faces of the ports are sufficiently true / flat then it would allow you to nip up that port back to the head.