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Engine damage from running without exhaust system?

Discussion in 'The Hokey Ass Message Board' started by poboyross, Mar 23, 2010.

  1. poboyross
    Joined: Apr 29, 2009
    Posts: 2,133


    I'm finishing up installing a 283 in my 50 Chevy, and was recently told that I shouldn't be running the motor without exhaust pipes/muffler because it can cause damage to the engine. Is that true or just some BS? All I really need it to run for is to warm up enough to open up the thermostat and get the engine refilled with coolant, finish setting the points, and testing out the carb.

    thx! :)
  2. Mr. Mac
    Joined: May 16, 2005
    Posts: 1,652

    Mr. Mac

    BS in my books.About the only thing that might hurt an engine is to run with no exhaust manifolds at all and then when the engine cooled it could warp the valves.My two cents.
  3. 57JoeFoMoPar
    Joined: Sep 14, 2004
    Posts: 3,931


    This has been dealt with here many times. I'll echo what Mr. Mac said. However, personally, when firing a fresh motor, I'd much prefer to have a full exhaust system, especially with mufflers. The reason being you'll be able to hear the motor and anything audible that might hint to troubles during break in that the gauges aren't telling you.
  4. BudJ63
    Joined: May 3, 2009
    Posts: 70

    from Florida

    I was told back when, that the open exhaust ports (no manifold or headers) let cold air hit the valves when shut down, and could warp them as Mr Mac said. Whereas the heated pipes would keep the atmosphere warmer til the valves had a chance to cool down. If its got headers or manifolds but no exhaust system, I wouldn't worry about it.
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  5. HemiRambler
    Joined: Aug 26, 2005
    Posts: 4,033


    I've heard many times about the possibility of warping the valves...if that's true then it puzzles me how they didn't warp when you STARTED the motor???
  6. 1930roadster
    Joined: Nov 9, 2009
    Posts: 321


    Oh i hate that tale... I'd bet the guy that started that owned an auto exhaust shop back in the 40s. I tried on Harleys and my old big block Chevy... open, on the street and in the cold, i tried real hard too ;)
  7. johnnie
    Joined: Jan 7, 2009
    Posts: 494

    from indiana

    My only concern would be running it too lean.
  8. propwash
    Joined: Jul 25, 2005
    Posts: 3,858

    from Las Vegas

    fresh quiet an exhaust system as possible so you can hear the actual mechanical parts of the engine. After "sea trials" then you can break it back to just headers. There is some danger of valves that cool too quickly tending to warp - ask any A&P or even experienced pilot about coming down out of the higher altitudes too quickly if you doubt me. Headers are just a good idea from a scavenging designe don't really want a bunch of flames shooting out of your heads anyway...cops might let the noise slide - but you'll be scaring the dickens out of the uninitiated and pissin' off the tightasses.

  9. mart3406
    Joined: May 31, 2009
    Posts: 3,055

    from Canada

    Jeez???. When will this old wives tale die???? No, running with an open exhaust and/or straight pipes will not hurt your engine, cause your valves to burn, bring on the 'heartbreak of psoriasis' or do any of other numerous ridiculous 'bad things' that it supposedly causes. It likely won't make any more power or cause your car to run any better or faster than if it had a properly designed, 'muffler equipped 'exhaust system either, but that's another matter. The worst it will do is likely piss your neighbors off, gain you a few tickets for excessive noise and damage your hearing, but that's all!

    Last edited: Mar 23, 2010
  10. zzford
    Joined: May 5, 2005
    Posts: 1,487


    Nope, it's crap. think about it...You have a big ol' hunk of iron that's real hot... air wafts into the port... which gets the temperture change fastest, the big ol' lump of iron or the air?
  11. poboyross
    Joined: Apr 29, 2009
    Posts: 2,133


    LOL....well, at least I don't have to worry about the Psoriasis. It's not a "fresh" engine by any means. It's already been broken in for some years now, I just gave it a check up, replaced all the gaskets, and tightened her up correctly.

    THANKS for all the replies. I amazes me how many "BS tales" there are, from a "noob's first build" perspective.
  12. 59ab
    Joined: Feb 19, 2009
    Posts: 220


    I don't buy it either. Have been hearing this for years but nobody can tell who it happened to.
  13. ...a little tip on your thermostat, drill an eighth inch hole in the flange, then install, this will allow it to purge the system of any air and it won't burp out the cap or overflow on the first startup. This won't hurt normal use thereafter.
  14. Won't hurt the engine at all,,,,,but it may sterilized the operator... :)
  15. metalshapes
    Joined: Nov 18, 2002
    Posts: 10,632

    Tech Editor

    On certain '60s Ferraris it said in the Workshop Manual to take off the headers and run it without.
    So you could measure at which distance from the head the color of the flames changed.

    This was to check the mixture of the carbs ( and the synchronising between the carbs )

    The Italians must have had better valves than the guy who came up with the bent valves story... :D
  16. Von Richthofen
    Joined: Oct 28, 2009
    Posts: 246

    Von Richthofen

    I totaly agree ..
  17. David Chandler
    Joined: Jan 27, 2007
    Posts: 981

    David Chandler

    I can remember stock cars running with nothing at all for an exhaust system. Just flames belching out of the ports. They kept coming back week after week, and I doubt if they had to do a valve job every week.
    That said, to me I'd think it would be a fire hazard, or at the very least some fried wires sooner or later.
  18. 61falcon
    Joined: Jan 1, 2009
    Posts: 774


    if its true, how do you explain all the cars at all the dragstrips running no exhaust. just headers.
  19. fab32
    Joined: May 14, 2002
    Posts: 13,990

    Member Emeritus

    TOTAL BULL SHIT!! With the exception of the suggestion it would be better to be able to hear any potential noises that indicate a problem.

  20. hellcat666
    Joined: Sep 8, 2005
    Posts: 265


    i agree that running the car like that realy isnt guna hurt it, but not necisarily tru about it not running any better, or faster, your motor will def run differntly with a full exhaust than with just open headers, running open headers can also effect you fuel air mixture. not hurt but change. dragsters and race cars are set up and have carbs that allow them to run and make most power with minimul exhaust, but if ur trying to daily drive the car, or even drive it 30 miles once a week to a cruz night, running a full exhaust would def make the car run better in this case. just my thoughts
  21. TurboShadow
    Joined: Feb 1, 2009
    Posts: 187

    from Prosser wa

    I think this old wifes tale only applies to those goofy wankel engines...
  22. mart3406
    Joined: May 31, 2009
    Posts: 3,055

    from Canada

    The 'open exhaust' damage myth doesn't apply to
    *any* internal combustion engine. And this particular
    lie has been making the rounds long before Wankels
    were even thought of. What makes you think an
    open exhaust would damage a Wankel??

  23. carcrazyjohn
    Joined: Apr 16, 2008
    Posts: 4,846

    from trevose pa

    Probably a disgruntled neighbor

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