Exhaust problem.

[Bob Dunahugh]

Seen this before. Jim K has a point. It seems that for some reason in our GMC's. I've heard an harmonic's from the exhaust. I had a 5 month old, double wall muffler come apart. At the seem that goes the length of that muffler on our 78 Royale. Got the aluminum skin on the bottom so hot. It started a fire in the foam. I then put an aluminum heat shield about 1 inch below that thin aluminum skin. That 1 inch is a MUST. Next. I put in 2 heavy welded steel mufflers in. I'll never have sheet metal mufflers again on anything we own. And while you're under there. Don't forget a gas tank heat shield. I made mine out of some aluminum that I had around. Another couple of my Comfort Zone things..
Bob Dunahugh
78 Royale since 2003

 

[jim kanomata1]

Bob,
Great idea to install heat shields, however we seem to get slightly better
rejection of heat from galvsteel.
I’m sure you went with Al to keep wright down .

On Sat, Jun 6, 2020 at 11:46 PM Bob Dunahugh via Gmclist <

> Seen this before. Jim K has a point. It seems that for some reason in our
> GMC's. I've heard an harmonic's from the exhaust. I had a 5 month old,
> double wall muffler come apart. At the seem that goes the length of that
> muffler on our 78 Royale. Got the aluminum skin on the bottom so hot. It
> started a fire in the foam. I then put an aluminum heat shield about 1 inch
> below that thin aluminum skin. That 1 inch is a MUST. Next. I put in 2
> heavy welded steel mufflers in. I'll never have sheet metal mufflers again
> on anything we own. And while you're under there. Don't forget a gas tank
> heat shield. I made mine out of some aluminum that I had around. Another
> couple of my Comfort Zone things..
> Bob Dunahugh
> 78 Royale since 2003
>
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--
Jim Kanomata
Applied/GMC, Newark,CA
jimk
http://www.gmcrvparts.com
1-800-752-7502