Exhaust pipes over-heating

Just a couple suggestions:

Are the new mufflers cheaper? Perhaps the old ones were double-walled the new ones aren't.

Are the new mufflers significantly different, perhaps a heat shield got thrown out instead of being put back where it was supposed to go.

Is there any openings for air to be introduced into the exhaust system and perhaps causing a secondary burn in the muffler? Maybe they broke a seal when putting the new ones on?

Ted

Check the vacuum advance can on the distributor- if it fails (and they do... all too often) then the engine won't be getting enough ignition advance during light-load and cruise conditions, and the exhaust will be staying a bit on the hot side. With the engine at fast-idle (1500-2000 RPM), disconnecting the vacuum line from the advance can should produce a noticeable drop in RPM. If it doesn't, check the can by sucking on the vacuum line and seeing if it holds vacuum. If air moves through it freely, its time for a new advance canister (the diaphragm is torn). If it holds vacuum, then make sure its connected to the correct port on the carburetor and that the carb is supplying vacuum (the port may be clogged).

Also, check the basic timing. Its a good idea to first verify that the timing mark on the harmonic balancer is right, and this can be done with a piece of coathanger wire inserted into the #1 spark plug hole and feeling for when the piston reaches TDC as a helper rotates the engine with a breaker bar.

But be aware, any time you ask a 440 to work hard, its GOING to heat up the tailpipes pretty good no matter what. The pipes should be routed well clear of anything that is heat-sensitive. I wouldn't be worried at all about the "bluing" of the clamps and mufflers (especially if they weren't aluminized or stainless steel mufflers) so the only problem might be the routing of the pipe near the tank that melted.

Thanks one and all for suggstions. Will check timing. The only problem i gave with that is I don't know what it is supposed to be I have no reference for this. Right now I have the timing set (withiut vac, adv connected to engine, idle advance is 27 deg adv., 36 degs at 2000 RM. I put this rebuilt motor in three yrs ago and the rebuilder set it like this to avoid burning a piston. Will check farther into the timing situation. BY the way i am in Calif. and the smog restrictions re horrific. Thanks again to all.

I forgot what year your M/H is, but for most years 440's typically like around 12 degrees initial advance (at idle, vacuum advance disconnected), and 36 degrees total mechanical (vacuum disconnected) for a stock distributor.. It sounds like you're fine on mechanical (27 initial isn't too much of a problem depending on what advance springs you have in there, the 36 total is the important number). I'd check for the dead vacuum advance canister, because a 440 will purr along under minimum load with about 50 (!) degrees total vacuum+mechanical. That will cool the exhaust temps down and help with fuel efficiency, although I doubt you could ever pull enough vacuum in a big boxy motorhome to get the full vacuum advance. You still should get *some* help at cruise, though.