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Ever see this happen before?

Discussion in 'The Hokey Ass Message Board' started by oldscout, Nov 21, 2010.

  1. oldscout
    Joined: May 19, 2010
    Posts: 31

    from NE PA

    Picked up a 72 Pontiac 400 for my 54, and started to break it down today. The number 3 exhaust valve, and numbers 4 and 6 have cracks in them. The bores look good, and everything else looks normal. Could this be from over heating? I'll try to upload pictures of the two heads, and was just wondering if anyone has seen this before. Thanks

    Attached Files:

  2. 73RR
    Joined: Jan 29, 2007
    Posts: 6,655


    Oh yeah, that puppy was hot.
    Be sure to mag the heads when you rebuild them.

  3. Would you believe those are very rare self seat cutting valves. They have rotators for the valve spring retainer like a big block Chevrolet, and as the valves rotate, they keep a constant fresh seat angle cut.
  4. dirt slinger
    Joined: Jan 30, 2010
    Posts: 645

    dirt slinger

    I actually seen this on a used race motor I had bought. Valves were discolored and one had a crack like yours. As 73RR said be sure to have those heads checked real good.

  5. squirrel
    Joined: Sep 23, 2004
    Posts: 50,274


    Burned valves have been around for a long time.....

    I have seen three on one engine before, a 53 buick 322 V8.
  6. R Pope
    Joined: Jan 23, 2006
    Posts: 3,309

    R Pope

    My 330 Ford truck engine had three like that, but worse. I chucked the heads for 352 car heads and manifolds. Like they say, check those heads real close before you spend any cash on rebuilding them. Cracks, warping, all that fun stuff is a possible byproduct of that much heat.
  7. OahuEli
    Joined: Dec 27, 2008
    Posts: 5,105

    from Hawaii

    I've seen those! They were on the same Pontiac factory spec sheet as the dual overhead cam turn signals!
  8. propwash
    Joined: Jul 25, 2005
    Posts: 3,858

    from Las Vegas

    ...and the triple underslung muffler belts...
  9. OahuEli
    Joined: Dec 27, 2008
    Posts: 5,105

    from Hawaii

    Forgot about those, one year option ya know...
  10. 28dreyer
    Joined: Jan 23, 2008
    Posts: 1,167

    from Minnesota

  11. Wow, yeah. Simple burnt valves, like others have said check out those heads before re-building!!

  12. snap too
    Joined: Dec 13, 2005
    Posts: 259

    snap too
    from lost wages

    Actually there are cases of minute spot welds being formed on exhaust valves that will cut the seat area. No bull, a friends shop had a contract to supply the GSA with rebuilt heads and short blocks at the Nevada test site,many of the heads he got back as exchanges or cores had the seats receded into the head as much as 3/16". It was being caused long periods of idling by security vehicles using unleaded fuel. On close inspection with a magnifying lens ,one could see the small weld spots and as the rotators did their job, the seats were eroded !
  13. gas pumper
    Joined: Aug 13, 2007
    Posts: 2,956

    gas pumper

    To answer the OP's question, this don't neccesarily mean overheating as in water boiling. This is hot in the combustion chamber, maybe from too lean or retarded timing.

    A 1972 engine is already a smogger, I would have thought this would have better material for valves to withstand the abuse that the 70's gave. Retarded timing and really lean mixes.

    Another thing to consider, I had a 235 Chevy that was an oil burner, and it was pretty happy except for the smoke. Back in the early 90's they added the MTBE here and the first tank of that shit, the combustion chambers got so hot, all the oil crud burned off, went out thru the exhaust valves and screwed up the seats so there was 0 compression. Towed her home.
  14. espo35
    Joined: Jul 16, 2010
    Posts: 310

    from california

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

    from Canada

    Ha! Big deal! Henway had both those
    features long before Pontiac! Those
    thieving, 'Johnny-come-lately', so-called
    'engineers' at Pontiac stole both of those
    innovations - the 'self seat-cutting valves'
    and the 'dual overhead cam turn signals'
    from Henway well as a bunch
    of other great Henway automotive firsts too!
    At Henway Motors Corporation, we've always
    prided ourselves on our use of the very
    latest advances in the fields of 'alchemy',
    'crypto-technology', 'pseudo-science'
    and 'advanced metaphysics', to constantly
    push the envelope of modern automobile
    design and provide our customers with the
    most technologically complex and mechanically
    contumacious vehicles possible! Not only did
    HMC engineers invent 'self-seat-cutting valves'
    and 'dual overhead cam turn signals' -
    we've had both of those features on all of our
    cars, going back as far as 1949 ....way, way
    before Pontiac ever had them! And that's not all
    either! Beginning with the 1950 models even -
    and continuing right through to all of our current
    2011 production models too - all Henways come
    with several other unique and even more
    complex, cutting-edge innovations....and all as
    standard equipment too! Things like, self-aligning,
    high-speed, 'muffler bearings', innovative,
    cross-compound-coupled 'flux capacitors',
    special, hammer-forged 'thorndykes', made
    from rare, imported, extra-stellar-sourced,
    dilithium-plated kryptonite(!):)eek:) - and even
    'far beyond state of the art', ultra-high-efficiency,
    sodium-cooled 'frazzle shafts' with 'rich Corinthian
    leather-lined' gimbal locks(!!):)eek::eek:) - all Henway
    firsts by the way, and things that Pontiac, even
    at their supposed 'innovative height' during the
    so-called 'Muscle Car-era' of the 1960's', never
    ever had! :eek::eek::D

    Mart3406 ('Official Henway Motors
    Corporate Historian and Archivist
    Last edited: Nov 26, 2010
  16. The " self seat cutting valves " were a extremely rare option on the RAM AIR MACH 5 Cylinder heads. The set you have were the rarest, they had only one cutter groove and were very unbalanced causing excesive valve guide side loading and wear as they roated. This of course prevented " concentric " valve seat cuttage. The RAM AIR MACH 5.2 had two cutter grooves spaced 180 degrees apart to eliminate the unbalance during rotation, and premature valve guide wear, therefor allowing for a concentric seat cut. Ive been told, the SERDI Corporation bought the technology from Pontiac Motor Division, and soon thereafter the company began to manufacture thier own line of valve seat cutting machines. Rumour has it that some of the original MACH 5 heads went to Japan in the mid 1960's, and were used in a experimental type race car to be featured in a new television series. BDM
    Last edited: Nov 22, 2010

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