exhaust manifold donut

[Layne02]

Hi everyone, my question is about the exhaust manifold donut gasket. A while back I installed a reproduction stock exhaust on my 87 . I ordered new donuts but they were different from mine , seems like they had a metal sleeve on it and mine do not, so I reused old ones. Well now I have decided to put a dual exhaust on it and was wondering if anyone has ordered new ones and where they got them. Thanks

 

[Honky Kong jr]

Did you consider headers?

 

[yevgenievich]

Check for 95 g20 van. I have one g20 manifold and it is different from stock gasket.

 

[rpcraft]

Yeah and it's dissapoing to say but at various points over the smog era GM really did change the manifolds some from year to year and even though the askets should be the same it always has made me question their fitment.

 

[Rusty Nail]

Yes. I have found that there ARE different sizes. I think I was offered two.

I bought mine @ O'Reillys.

 

[bucket]

Last time I bought donut gaskets, the parts guy just had me go back to the parts shelves and match one up. He said it was a waste of time looking it up by application. He was a good parts guy.

 

[RustyPile]

Donut gaskets come in two configurations.. One has a steel sleeve attached to the I.D. and is approximately twice the depth of the gasket.. The sleeve fits into the exhaust pipe and prevents the donut from collapsing... The other type donut doesn't have the sleeve.. It requires an exhaust pipe that has the sleeve attached inside the flare..

The exhaust pipe size and configuration, the donut gasket, and the exhaust manifold all have to match in size..

 

[rpcraft]

I didn't think to ask because I ditched the stock stuff ages ago but I had to go back and look at some pictures and remind myself are you talking about the drivers side or passenger side? The reason I ask is the passenger side had that thermo-valve thing on anything up to 85 at least (because I had a 77 and it had it until I swapped to headers, and then my 85 had it too until i tossed the exhaust in the trash too... If you are missing that valve it will never mate up properly and I think that requires 2 gaskets??? Someone help me out here.

 

[RustyPile]

You're talking about the heat riser valve.. Manifold to heat riser valve requires a flat "three sided" gasket.. A donut gasket is used between the valve and the exhaust pipe.. The studs in the passenger side manifold are longer so that everything can be "sandwiched" together.. The early valves were spring loaded.. the shaft for the "flapper" part is off center.. The spring holds the valve closed and exhaust flow pushes it open.. Later models have a vacuum operated valve.. In the past, I have seen donut gaskets that are flat on one side and tapered on the other.. All the gaskets I saw in this configuration had a sleeve sticking out the flat side..

 

[Rusty Nail]

I remove the "flapper" and put it back together.

 

[bucket]

Later fuel injected GM's often had a dummy (empty) heat riser. Like TPI Camaros and I think the TBI models too. Can't remember for sure. I don't remember if the trucks had them or not. Headers for all!

 

[Layne02]

Mine were like the one that has the metal sleeve but did not have the sleeve. They slid over the exhaust manifold outlet. So the metal s!we've was in the way.

 

[twinturbo427]

Always save the flanges and at least 6" of pipe stub if reusable. You can save some bucks at the exhaust shop if they don't have to make them.

 

[Rusty Nail]

Headers for all!

Hooray!

 

[peats]

put some long tube hedders on the thing and get some low end grunt. maybe 30 ft lb of torque. thats real bang for your buck.