MGB Register Forum

I shall shortly refitting the OE cast iron exhaust manifold together with a new SS exhaust. Having looked at various publications , spares suppliers &
quite a few forum discussions , i am undecided which way up the 2 seals (yokes/ GEG753) go in between the manifold & the down pipes. Is it metal up or insulation material up? The seals are designed to be crushed on assembly to make a fume free joint.
Cheers,Charles

Well, I cannot say positively which way is correct, but I can state which way works, and why I do it that way.

I put the metal side up, because when/if replacing, it's a lot easier to scrape any remnants of the donut off the pipe, than from out of the manifold while working upside down. I've never had any problem with sealing, regardless of orientation.

Some of the replacement donuts have no metal side, so that eliminates any guesswork.

BTW, GOOD CHOICE! I've had quite a few MGBs & GTs in the past fifty (50) years, and tried a variety of tube headers; eventually, they all leaked and sever cracked in various places. The OE cast manifold__assuming '62-'74 versions__is the best choice.

Hi Randy,
Thanks for your feedback.
I'm going to fit them metal up,having done a trial fitting with both the manifold & downpipes off the car, although not bolted them together.
I still have to clean up the inside of the manifold to be able to slide in the tips of the downpipes without too much agro.A job easier with the manifold off the car (particularly when I don't have a lift)!
Cheers, Charles

Can I recommend that you re-tighten the exhaust manifold bolts after about 500 miles?
I had to replace the exhaust manifold crush seals when we arrived at the European Event of The Year in Italy earlier this year - fortunately I was carrying them as spares anyway. About 1,800 miles (3 months) later the exhaust started blowing again so I was expecting to replace them (again), assuming I had done a poor job, only to discover that the 6 nuts needed tightening!

Thanks Paul,
I intend to check the tightness of all the fittings once I have completed some reasonable mileage.
Just finished fitting the entire exhaust system which is not the easiest thing to do when the car is on axle stands & not
on a hoist!
Cheers,Charles

Don't over tighten the nuts.

They should be of brass and no more than 20 newton metres.

The same as for the six nuts where the manifold joins the twin pipes.