Exhaust manifold to exhaust pipe questions

[Charles P.]

Here is a picture of the upper pass side exhaust pipe. It has a flange around the perimeter that the donut gasket sat in (now removed). It did not have a spacer present. My question would be is it necessary to use the 3 inch spacer, which is shown in the AIM, with this set up?

The spacer I understand is to keep the donut seated but isn't that what the flange is doing? Above this will be the flapper valve and then the triangular gasket that seals to the bottom of the exhaust manifold.

As a side note I was unable to salvage the AIR tubes. I had posted earlier I had an exhaust leak on the rear tube and was trying to remove them. No problem since I was able to find another set in mint shape. Once I get the gaskets I will put it back together. What order would you button it up in? Place the exhaust mani first or attach the exh pipe to mani then seat the manifold? Thanks.

[Joe L.]

Re: Exhaust manifold to exhaust pipe questions

Charles-----

The only spacer I know of that was ever used in approximately the same location you are referring to is the spacer used for 63-65 FI and 67-69 L-88. This spacer replaced the heat riser valve which was not used for these applications.

I think the part that you are referring to is the EXTENSION. In your case, the extension is an integral part of the forward exhaust pipe as seen in your photo. No separate extension is required nor could one be used even if you wanted to do so.

As far as the order of assembly goes, IF YOU HAVE THE FORWARD EXHAUST PIPE IN THE CAR AND CONNECTED TO THE REAR EXHAUST PIPE, it might be easier to loosely connect the forward exhaust pipe to the manifold and heat riser first. Then, bolt up the manifold to the engine and, finally, tighten the 3 exhaust flange nuts.

[Charles P.]

Re: Exhaust manifold to exhaust pipe questions

The extension or what I referred to as a spacer is shown in the AIM as #5 in this schematic. I was trying to follow the AIM and was under the impression that this was a removable part. In my case the pipe is as you say, one integrated part, so no extension needed. Thanks for the information. Like an itch you can't scratch, I'm hopeful that this exhaust leak will be nixed once and for all (and not appear somewhere else).

[Joe L.]

Re: Exhaust manifold to exhaust pipe questions

Charles-----

Your forward exhaust pipe may be a later GM replacement or, possibly, an aftermarket part. Through at least 1969 and likely for at least 2 or 3 years thereafter, the forward exhaust pipes did not include the integral extension. Later PRODUCTION and SERVICE pipes, which also became SERVICE for earlier applications, often did have the integral extension.

Some folks without integral extensions often omit the separate extension as "unneeded". Believe me, if it was "unneeded" GM would never have included it. The extension serves to protect the exhaust packing ("donut gasket") from direct exhaust heat and also helps to insure that the packing is properly centered. I'd never assemble a system without either the integral or separate extensions.