exhaust donut

[Dale S.]

I found an exhaust donut, it is a typical looking 2 inch Asbestos donut, but it is on a metal cone that necks down to 1 1/4 inches. I removed this from my 67, 327 when I replaced the original exhaust in the 70's. Were there 2 of these or was it on one side or the other and what was its purpose? I could not find it in the reproduction catalog's that I have. Thank you Dale

[John O.]

Re: exhaust donut

Hi Dale

Donut gaskets are on both sides of the engine. Their purpose is to seal where the exhaust pipe and the exhaust manifold connect to each other.

John

[Gerard F.]

Re: exhaust donut

Dale,

Maybe that's a special donut for the AIR car. I don't remember seeing an asbestos donut with a neckdown on my 327 non-AIR.

Jerry Fuccillo

[Chas Henderson #28127]

What is the best type of donut? *NM*

[Joe L.]

Re: exhaust donut

Dale-----

The part to which you refer is called an EXTENSION. It is used for all original small block exhaust systems. Many replacement systems have the extension welded to the forward exhaust pipe, so there is no need for a seperate extension. The extension is a necessary component for several reasons. For one, it ensures that the donut gasket is not displaced. For another, it shields the donut gasket from direct contact with exhaust gasses and, in doing so, improves the seal and the longevity of the seal.

There were 2 differet extensions used for 2" and 2-1/2" exhaust systems. The 2" system extension, GM #3890382, is still available from GM. However, you can find these pieces easily in the exhaust section of most auto supply stores. They are a VERY common item.

[Joe L.]

Re: What is the best type of donut?

Charles-----

Sintered iron. Not original for any C1, C2, or C3 to about 1980, but the best.

[Dale S.]

Re: exhaust donut

Thank you Joe, I am not clear on how the dome protects the gasket. Does it extend up into the manifold or does it extend down into the exhaust pipe. Either way it looks as if the 1 1/4 inch opening would restrict exhaust flow. I dont remember wheather the Walker exhaust that were going obsolete had them in the header pipes or not. I just know they all pipes,mufflers,clamps and hangers were 1/2 of W.D. price. After looking at this, it must have gone down as it would hit the heat riser if it went up. The dome or cone extends 1 1/4 inches down or up from the gasket. I have never seen one of these with this large cone as W.D. salesman for a automotive warehouse or at my store(we stocked AP. and Walker at differnt times). Joe, did you get my email on the Whittek clamps? Dale

[John H.]

Re: exhaust donut

Dale -

Sounds like some oddball aftermarket thing, or a part for some other car; no such device was ever used on a Corvette.

[Joe L.]

Re: exhaust donut

Dale-----

The extension is (or should be) a swaged down piece of mild steel tubing about 1-1/2"-2" long. There is a larger diameter section on one end and a smaller diameter section on the other. The smaller diameter section fits DOWN into the throat of the exhaust pipe. It can only go so far down because the larger diamter upper section "bottom" and prevents further entry into the pipe. The donut gasket then fits AROUND the larger end of the extension. A short section of the extension protrudes up into the manifold outlet. That's it; it's as simple as that. Inasmuch as the extension is inside the ID of the donut gasket, it "insulates" the donut gasket from DIRECT contact with the exhaust gases. The gases pass THROUGH the extension and into the exhaust pipe. Of course, the HEAT fo the exhaust is transferred to the donut gasket, but NOT the direct contact of the exhaust gas with the donut. It also helps LOCATE the donut and prevent its displacment.

[Joe L.]

Addendum

The EXTENSIONS that I am talking about are pictured on page 58 of Paragon's 63-67 catalog. They are their items #4093 and 4095. The 4093 is the 2" extension; the 4095 is the 2-1/2" extension.

[Dale S.]

Re: Addendum

Thanks Joe, I will look at Paragon. Your discription sound right on the money. Glad everyone does not think I am making this up, I took them off the original pipes in the early 70's. What about the Whittek clamps? Possible to have 1/67 and 2/67 on a march 30 th car? Dale

[Dale S.]

Re: Addendum

Yes, That is them, they are also in the assembly manual under side exhaust, at the back. Thanks a lot Joe. Dale

[Joe L.]

Re: Addendum

Dale-----

I responded to your hose clamp question twice. Apparently, you have some sort of "screening" system on your e-mail that has prevented my responses from getting to you. To say the very least, and as I've said previously, I find it EXTREMELY frustrating to take the time to respond to questions and not have them get through because of folks' failure to deal with their e-mail screening problems. Generally speaking, I have a personal policy that I will not recompose a response that doesn't get through the first time because of this e-mail "screening" situation. In this case, because the response was short, I did send a second. Obviously, it didn't get through, either, and likely for the same reason that the first one didn't.

Anyway, I think that it's very possible, even likely, that the hose clamps as dated are original. There's no reason to think that clamps have to be match-dated; that wasn't among the factory protocols.

[Mike McKown]

Re: What is the best type of donut?

Ford used these as OEM in the late '60's.

[Brian M.]

Re: What is the best type of donut?

Don't ask a Cop this question.