Exhaust donuts

[joe_padavano]

I'll admit that I haven't worked on many 307s, but I was surprised to find that my 84 Custom Cruiser uses an exhaust donut on the RH manifold where the main down pipe exits. I knew the tubular manifold on the 86 307 used a donut, but I chalked that up to the fact that Olds couldn't cast a tapered seat into that thin sheet metal flange. The other side on that motor does have the tapered seat cast into the EFE valve housing.

Anyway, I had always assumed that the Olds cast iron manifolds never used donuts, which once again proves what happens when you assume...

This, by the way, was the source of my exhaust leak. The donut had completely disintegrated, leaving only the steel ring that fits into the manifold. The good news is that all three bolts came out of the flange. The secret there is to use an impact wrench and to hammer the next smallest socket over the rusted bolt head. Lots of anti-seize on the reinstallation.

[J-(Chicago)]

[quote=joe_padavano;36262. The donut had completely disintegrated, leaving only the steel ring that fits into the manifold. The good news is that all three bolts came out of the flange. The secret there is to use an impact wrench and to hammer the next smallest socket over the rusted bolt head. Lots of anti-seize on the reinstallation.[/QUOTE]

X2 on this one. worked for all of my bolts on the driver's side.
I still had to cut the pass side though.

[citcapp]

Originally Posted by joe_padavano

I'll admit that I haven't worked on many 307s, but I was surprised to find that my 84 Custom Cruiser uses an exhaust donut on the RH manifold where the main down pipe exits. I knew the tubular manifold on the 86 307 used a donut, but I chalked that up to the fact that Olds couldn't cast a tapered seat into that thin sheet metal flange. The other side on that motor does have the tapered seat cast into the EFE valve housing.

Anyway, I had always assumed that the Olds cast iron manifolds never used donuts, which once again proves what happens when you assume...

This, by the way, was the source of my exhaust leak. The donut had completely disintegrated, leaving only the steel ring that fits into the manifold. The good news is that all three bolts came out of the flange. The secret there is to use an impact wrench and to hammer the next smallest socket over the rusted bolt head. Lots of anti-seize on the reinstallation.

Joe,

Help me out here. I have installed X-Z stock exhaust manifolds on my 455 I am installing in my 57 Olds. This being my first Olds swap I assumed that this setup used donuts, if it does not what do I use to connect 2.5" exhaust pipe to my manifolds. Thanks in advance for the help

[marcar1993]

I believe it bolts right into it with a ball in socket type flange. The manifolds have the "ball" edge and the pipes should be "trumpeted" or langed out to seat the ball flange.

[83hurstguy]

the H/O has a donut in that spot, uses the bolts with springs going into the manifold. Only donut in the exhaust system AFAIK.