'65 300 4V Driver's Side Exhaust Manifold Replacement: Calling John Chapman!

Discussion in 'Parts wanted' started by sbrmd, Jul 16, 2004.

  1. sbrmd

    sbrmd Well-Known Member

    I've now cracked two of the above-mentioned items, the second one an expensively ceramic-coated one! Anybody have any better replacements they'd like to suggest/part with? John, I singled you out in the title of the thread because seems to me you have had something to say about 300 headers in the past. Know where I can find one?

    Exhaust clatteringly,
    Steve.
     
  2. Bill V.

    Bill V. Well-Known Member

    Cracking exhaust manifolds

    Steve, Curious if you used the french locks when you reinstalled your ceramic coated manifolds. I beleive most folks don't bother with them, cranking down on the bolts instead. This doesn't allow for heat expansion, the result is rather predictable. I think I might have a good drivers side manifold with a good set of used locks if you think you might want to give it another try. Let me know and I'll look. Bill V. Pnx. Az.
     
  3. sbrmd

    sbrmd Well-Known Member

    Interesting observation! They were not re-used. I remember seeing them on the originals, though - which were themselves cracked.

    In looking for the french locks, I just noticed that the pass side is also newly cracked!

    Do you think simply reinstalling replacements w/ french locks is a safe bet? Or should I try to find those rare-as-hens-teeth Poston 300 headers? In any event, thanks for the offer of a driver's side; I'm interested. Luckily I have a pass side extra, but would need french locks for it, too.

    Best,
    Steve.

    Best
     
  4. Mr Big

    Mr Big Silver Level contributor

    STEVE: Don't know if you have already tried this...but you should make sure both surfaces are "flat".

    I use a very large "Mill Bastard" file on every ex manifold to check for warping...if you can't find another manifold I'm pretty sure I have another set. Good luck!
     
  5. sbrmd

    sbrmd Well-Known Member

    Hey Glen!

    Thanks for the input. Yes, we machined them flat. Jim Weise worked on this for me. Also had them both ceramic coated, thinking that the old ones cracked from heat; guess that wasn't the problem. We're wondering now if the exhaust system isn't "hangered" correctly; or, whether the exhaust ports on the heads aren't quite flat. Hoping this last theory isn't it! And, there's the french-lock theory.

    Might take one of you guys up on a replacement. Still mulling over the Poston header idea. Do you guys think they'd be less likely to crack? Really don't want to keep shelling out for this same repair!

    Best,
    Steve.
     
  6. dcm422

    dcm422 Well-Known Member

    Can't recall if it was on this board or another, but John did a post on the manifold issue before.
    If I remember correctly, he seemed to think it was an overtightening issue that caused the manifolds to crack. The bolts are only supposed to be tightened to 10-15 ft lbs on aluminum heads (64) and 15-20 ft lbs on 65-67 300/340.
    Apparently, the manifolds are intended to be "loose" and move as the metals expand. Probably why the french locks were used to keep the bolts from backing out.
    My 64 still has the locks and original manifolds on and they seem to be ok (shouldn't talk too loud).
    Looks like we wrench the bolts down as tight as we can make them when we replace them and it doesn't allow movement, so they crack.
    I hope I quoted John's position correctly.
    Also, I have been around a lot of 300's in the last 36 years (ouch!) and never had a cracking problem. However I am a psycho who uses a torque wrench all the time and follows the specs. :grin:

    Regards,
    Mark
     
  7. Mr Big

    Mr Big Silver Level contributor

    I would say that the "lock Tab" theory is a good one.

    All of my 300's and 340's have them...mostly because they came with them...
    The headers you mentioned will most likely bring different issues into the game, such as regular painting and gasket replacement...not to mention the ever present re-torquing....

    Try the locks, check your hangers and maybe that will do it.

    I may have some extra locks too if you need them...

    FYI i've also used gaskets with some success....
     
  8. sbrmd

    sbrmd Well-Known Member

    Glen:

    You have e-mail and p-mail!

    Best,
    Steve.
     

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