Ok, so I came pretty close to getting the beauty back and running, but some things happened.

First, I have a cracked downpipe flange - or maybe it's called something else. This happened when I was putting the downpipes back in and torquing from underneath - I was going for 24 lbfs when it popped and I stopped.

Here's the pictures.




You can also see that the front pipe has a pretty big gap compared to the rear pipe. Visual inspection and it just looks off.

I've got new seal rings coming and am now wondering if that's enough or if I should use some Permatex hi-temp gasket, anti-seize sealant stuff.

Any insights, suggestions, comments, criticisms, etc. are totally welcome and will be returned in kind, plus beers and BBQ for those that can make it to Austin, TX

 

You can probably use the retainer as is, although if you're removing the whole downpipe you could weld it up.

I never torque to any spec on those. The sealing rings do collapse, so what's more important is to make sure that the downpipe is seated square into the manifold, and then tighten up the nuts evenly so that the retaining plate is pulled up evenly. I do it in stages and tighten just enough so there is no exhaust leaks. You'll hear a leak, or feel it with your hand when the engine is idling. Then try tightening a 1/4 turn at a time or even less. Just enough to seal it up is all you need.

The individual pipes can sit at different lengths into the manifold, that's perfectly normal. Try fitting the downpipe into the manifold on it's own, without the rest of the exhaust system connected if you can, and see how it fits. If you can get it aligned and seated square, then snug it up and hopefully the rest of the exhaust can be fitted. It's a bit of an iterative process to get everything seated and in it's happy place.

I have never found any of the products in a tube can stand up to exhaust temperatures. On a 4.2 XK engine I fitted an exhaust temp gauge just for my interest, and on a long mountain grade I pegged the gauge at 1100C. Consider that steel glows red hot at 750C...

 

Do not wary about it! This is only connection pressure plate. I hope that you put new gasket!

 

Just got a nice package of goodies from our favorite supplier including new sealing rings. Totally agree on getting the fitting correct and then doing slow torquing all around - you've gotta make sure things seal as level as possible. That was probably my problem the first time, coupled with also reusing the original sealing rings. Well, I'm also 50, lazy, 4 kids, wife, dog, cat, 67 MGB, and the damn heat shields get in the way, what a ...

 

I do them up from underneath, and I have a socket that incorporates a swivel. Works great for this, plus about 3' of extensions. A standard 3/8" ratchet is enough to do up the nuts.


Reusing the original rings was the problem, they are generally a one time use.

 

If you need new (used) pipes I have some around, it would involve some welding as theyre cut off in various places/lengths.

bright side is this will allow you to GUT those horrific and restricting fire hazard cats if fitted to your car.

 

In the early 90's catalytic converters were optional in the UK, and Jaguar published HP figures with and without cats for the UK market. The power difference was 1%, so not something you'd ever feel.

I put the Euro downpipes on my Series III v12 car and I couldn't tell any performance difference.

 

After 30 years of soot buildup I'd imagine that marketing number would look quite different.

I gutted my cats it was like switching from 87 to 94 octane gas. (I use 94 anyway)