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Old 06-04-2021, 01:49 PM   #1
barmanvarn
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connecting exhaust to manifold

Working on my dad's 1969 GMC C15 with an L6 (250?)......and excuse the perhaps dumb question......

I had to take the exhaust off to cut off the rotted out muffler and install a new one. I noticed the exhaust was very loose where it attached to the manifold. It hadn't been leaking and I didn't pay it much mind.

I've now put everything back together and do I have a leak at that point. What I'm wondering is it just that I didn't line it up well when reattaching or is there supposed to be a gasket of some sort?

The manifold end of the exhaust pipe has a rounded "ring" permanently attached about an inch from the end and that rounded ring seems to fit against/into a rounded indent in the circular manifold opening (hope I'm explaining that well).

So, am i needing some sort of gasket or is it just a dumb user installation issue?

thanks in advance
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Old 06-04-2021, 02:25 PM   #2
Breadstick
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Re: connecting exhaust to manifold

I think this round gasket is what you're talking about.

https://www.lmctruck.com/1967-72-che...st-pipe-gasket
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Old 06-04-2021, 02:28 PM   #3
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Re: connecting exhaust to manifold

Quote:
Originally Posted by Breadstick View Post
I think this round gasket is what you're talking about.

https://www.lmctruck.com/1967-72-che...st-pipe-gasket
Thanks. I had seen that but wasn't 100% sure about it. I guess for $3 I can order it and see.

thanks again.
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Old 06-04-2021, 03:39 PM   #4
Southcity
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Re: connecting exhaust to manifold

Since you'll be taking it apart again, replace what you can:

1. Gasket
2. Any bolts, washers etc.

It's a good idea to support the exhaust system (some wood blocks) prior to taking it apart. It will help when putting everything back together too, good luck!
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Old 06-09-2021, 12:05 PM   #5
barmanvarn
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Re: connecting exhaust to manifold

So, I ordered the gasket from LMC truck and it just arrived. I'll give it a try once the weather clears up but TBH this doesn't appear to be what is needed for this application.

This gasket looks like it expects two rounded edges on each side to mate to.....this doesn't match what my exhaust looks like where it meets the manifold.
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Old 06-09-2021, 12:34 PM   #6
Davidf
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Re: connecting exhaust to manifold

The gasket you ordered seems to be for a modern engine (LS). Yours is probably just a donut that slips over the end of the exhaust down tube. It may look like it is part of your downtube, but can be cut off and replaced.

The one you want probably should NOT have a metal sleeve that locates it in the exhaust manifold
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Old 06-09-2021, 12:37 PM   #7
Wrenchbender Ret
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Re: connecting exhaust to manifold

Some of these old truck had a bulge on the pipe & didn't use a gasket. It should tighten up when you tighten the nuts. You may need to clean the manifold where it seats. The studs might be rusty on up towards the manifold. Try putting some flat washers above the nuts & see if they will tighten up enough to seal the pipe.
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Old 06-09-2021, 12:43 PM   #8
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Re: connecting exhaust to manifold

Thanks for the comments/replies.

I had the same thought that the "bulge" that's part of the pipe probably serves as a permanent gasket and my current issue could just be an alignment problem.

It should stop raining this weekend so my plans are to adjust the pipe as is and see if I can fix the leak.

Since I do have this new gasket now, I've also order a new pipe adapter. I can cut off what I have now that attaches to the manifold and install this adapter which will accept the gasket I have.

thanks again and I'll keep you posted!
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Old 06-11-2021, 10:08 AM   #9
barmanvarn
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Re: connecting exhaust to manifold

Just wanted to provide an update that I resolved the issue.

Those of you that advised that my setup basically had a gasket already built into the exhaust pipe (permanently attached) were correct.

I looked closely and could tell it wasn't fitting correctly.

I loosed the 2 bolts and crawled underneath where I was able to move the exhaust around while pushing it up into the manifold. After a few seconds I got an audible SHUNK when I got the "gasket" inserted correctly.

Tightened everything down and now it's making a perfect seal.

Thanks everyone for the help!

Now to work on adjusting the carb (which I also know jack about) as it only stays running w/ the choke half open. Fully closed or fully open and it dies.

I"m sure I'll be creating a new post this weekend asking for help after I'm unable to get it adjusted. LOL
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Old 06-11-2021, 04:40 PM   #10
54blackhornet
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Re: connecting exhaust to manifold

Brian no question are dumb ! Everyone on this site started out as beginners at some point. I want to congratulate you for helping your father. Lots of knowledge to be gained from the good folks on this site. ..Jack
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