Exhaust pipes over-heating

Discussion in 'General Motoring' started by MEPCLS449, Jul 16, 2003.

  1. MEPCLS449

    MEPCLS449 Guest

    I have a 77 dodge 440 engine in a class C motor home. Had new mufflers
    installed and 600 miles later the mufflers are showing heat and the clamps
    holding the mufflers on are turning blue from heat. It appears to be worse on
    the right side.

    The tail pipe got so hot on the right side that it melted a hole in the plastic
    tank about 15 feet from the engne. The plugs are dark brown with some white
    down inside the electrode.

    The engine has good power and is getting 8 to 10 mpg does not get hot
    according to the temperature gage, the Radiatror top is 194 deg and the bottom
    tank is 174 deg. The fuel milage has always been in this range but I never
    noticed the pipes getting hot before.
    Any help someone may have will be greatly appreciated as I am stumped. Thanks
    in advance. Marvin
     
    MEPCLS449, Jul 16, 2003
    #1
  2. 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
     
    Ted Mittelstaedt, Jul 16, 2003
    #2
  3. MEPCLS449

    Steve Guest

    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.
     
    Steve, Jul 16, 2003
    #3
  4. MEPCLS449

    MEPCLS449 Guest

    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.
     
    MEPCLS449, Jul 17, 2003
    #4
  5. MEPCLS449

    Steve Guest


    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.
     
    Steve, Jul 17, 2003
    #5
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