Looks like you had one of those asbestos fiber donuts. Get the hard smooth ones. I think they are ceramic. They last forever or at least never burn out.
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'68 Parisienne 2+2 Convertible Matador Red (Resale Red but not for sale).
......there is nothing wrong with the gasket style you had there , but you have to keep an eye on them to make sure the flange is always tight, if it losenes up abit then it can blow out like yours did. The all metal ones are good too but do not seal as well if the manifold or exhaust pipe does not have a perfect seat. The asbestos type will form to any imperfection there may be in the seating area when tightened.
I agree. I don't seem to have a great fit on the Beaumont so have had to do some custom fitting and at first I blew a couple out but the one I have on now works great. Only thing is I have to snug it up every month or two.
The 6 cylinders seemed to have trouble with that quite a bit.
I would echo what Nailhead said about keeping it snugged up as well as the steel ring style not being as forgiving when it comes to a perfect seal. However, if you would spend some time and make the mating surfaces very nice, that steel one would likely last a very long time.
If you don't have luck locating a steel one, should you decide to use that, let me know. I can get you the GM number for it. I may even have one for you.
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1966 Strato Chief 2 door, 427 4 speed, 45,000 original miles
1966 Grande Parisienne, 396 1 of 23 factory air cars (now converted to a "factory" 4 speed)