Hi,

I just picked up a 1968 Cutlass S and a previous owner put in a 1972 455. They also put in an exhaust system not too long ago by the looks of the pipes, but I've got leaks at the exhaust manifold flange. I pulled out a bad donut gasket on one side and I've been looking for a replacement. Every retail place comes up with a 2-1/8" ID gasket for that engine but they don't fit. The one that I took out is more like 2-3/8". I've looked just about everywhere to find something and I've come up with nothing. It doesn't help that no one advertises the ID of the gasket. They're stock manifolds so I don't know what I'm missing. The gasket that's supposed to fit does fit at the pipe, but the metal ring is too small that's supposed to go to the manifold as I've mentioned. Then I came across this thread that says that there are no donut gaskets so I'm even more confused. Has anyone else run into this?
Any advise would be greatly appreciated......

 

Yes, most Olds don't use a donut gasket. There a couple of exceptions..You're not alone, we have many threads on this.

The flange area is metal to metal. Its all about the flange on the pipe joining the flange on the manifold.

Try this, loosen the two flange bolts enough to wiggle and jiggle the joint. Re tighten.

 

What manifolds do you have on your car? The A-body W/Z manifolds do not use donuts, they are metal-to-metal seals. Some of the manifolds used in the full size cars DO use donunts, and in many cases the correct size is no longer available. I've run into this problem on my 67 Delta. I found out of production donuts that I was able to make work, but you may be forced to adapt something. Of course, the right answer is to get the correct A-body manifolds, so this problem goes away.

 

Hi Don 71 & Joe,

Thanks so much for getting back to me so quickly!!! I ended up going away for a long weekend on short notice so I haven't been able to check into things. I will look up the manifolds to see which ones they are and go from there. I think someone used their own make-shift gaskets and they didn't put enough hangers on the exhaust so it moved around too much and that didn't help things. I was able to save the metal part of the gasket and I found one that was close at the auto parts store. I was able to press the metal into the gasket so the top did seal. Then I used a belt sander to reshape the gasket to the smaller diameter that I needed. I started it up and it did leak but I may be able to rework it a little more if I have to use gaskets. I'm not going to spend much more time on this because I'm hoping to put in another 455 motor that was built with a lot more HP and add headers. So, I really just need to get this sealed so that I can get an inspection sticker so that I can drive it until that happens.

Thank you once again and I'll let you know how I made out when I get back on the project Monday.

Take care,
Brian

 

Just to update...these are W/Z manifolds. Not sure why they had donut gaskets in them, but looking at the rest of the exhaust it doesn't surprise me. It looks like someone's first day at welding class :-) I was able to get a good tight seal with my primitive customization, since I already had them in. Thanks again....next up, headers!