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Technical Shedding valvetrain on 389 Pontiac heads.

Discussion in 'The Hokey Ass Message Board' started by Ironmonger, Aug 29, 2014.

  1. Ironmonger
    Joined: Oct 9, 2009
    Posts: 67

    Ironmonger
    Member

    Back to my 64 Bonneville. Wrapping it up for a 1400 mile journey to Bismarck ND. I am disassembling the heads, cleaning the valves, relapping them, etc. Are the spring oil shields and inner dampening springs necessary????????? Many performance builds I see never re-install these parts and aftermarket springs do not come with inner dampeners as far as I can tell. Can I shed these parts and be ok while lightening the valvetrain a little???? thanks guys :)
     
  2. Those items were left out by the shop that did my SBC heads ealier this year. Not something I would have thought to do, but no problems.
     
  3. I wouldn't leave out the dampers. They are there for good reason AND aftermarket springs have them as well. IF you have switched to good umbrella seal or Teflon seals on the valve stems you could leave off the outer shield without suffering any ills and that is IF. What will you gain? Nothing you can notice. About the same as an ugly girl in a pretty dress.
    don
     
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  4. Ironmonger
    Joined: Oct 9, 2009
    Posts: 67

    Ironmonger
    Member

    I haven't switched, it requires machining which I have no time for so I am stuck with the rubber O-rings :( do the big metal shields really help that much?, I have always heard otherwise.
     

  5. yellow dog
    Joined: Oct 15, 2011
    Posts: 453

    yellow dog
    Member
    from san diego

    It sounds like time is an issue....if so I'd recommend not touching the heads except cleaning the
    mating surface. If the heads don't have hardened exhaust seats, removing the lead oxide residue (assuming lots of leaded-gas miles) from the valve/seat will hasten seat recession. Cleaning the
    valve stem/guide area of baked on varnish could allow more oil migration down the intake valve. Wait and do it right with hardened seats, knurled guides, teflon seals, spring pressure blueprinted and definitely dampers, etc. Old engines are sometimes better untouched
     
  6. "do metal shields really help that much?,"
    They are necessary with the o-rings otherwise the splashing oil has a direct path to the vale stem and with manifold vacuum down the hole into the engine. The umbrella would take the place of the shield in a different sort of way. There are sealed power umbrellas that would work. 302 Ford for instance have the same .343 stem size and are an umbrella seal that requires no machining, if you are hell bent to do this but it wont work with the stock o ring seals.(removing the metal shields)
    After over 45 years at this both as a hobby and a profession I have learned that while not everything the factories do thrills me but however they do it they do it well. We in the hotrod hobby have a tendancy or an inclination to change things. Sometimes for no good reason. Removing the shields will gain you nothing and will in all likely hood cause you headaches with foulded plugs and smoke after idling or on decceleration. You have two options. You can take sound advice and leave it alone or the same as it was with good results or you can forge ahead and try it for yourself. It will be a learning experience for sure but its value may exceed its inconvenience. Me I learned both ways. Sometimes doing stupid things and rethinking it and sometimes following a good idea to the end. However there needed to be a prize at the end of the rainbow, In this case there isn't. The shields are not hampering your performance in anyway yet in a basically stock engine. You would have to push it a long way from here before they would.
    Your dime , you decide.
    don
     
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  7. Ironmonger
    Joined: Oct 9, 2009
    Posts: 67

    Ironmonger
    Member

    My nos GM engine gasket kit ( early style packaging) has umbrella seals in it, what are these for????? later engines or will it fit mine?.
     
  8. rustyangels
    Joined: Sep 28, 2010
    Posts: 178

    rustyangels
    Member

    similar but years ago, there was a magazine's tip, to use valve stem 'umbrellas' from a Studebaker on a SBC to help reduce oil consumption
     
  9. stimpy
    Joined: Apr 16, 2006
    Posts: 3,547

    stimpy

    leave the sheilds in place if you do not change to a better positive seal and use the o ring on the top of the valve stems by the locks as Pontiac valve stems are a little loose on the clearances from the factory and when you eliminate them it smokes like a broken ring on deacell and leave the dampner in the spring pack as it absorbs harmomics from long periods of continous rpms which will cause the valves to do weird things , if Gm didn't intend it to be there they wouldn't have wasted the money putting it in there to begin with . nature of the beast .
     
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  10. Ironmonger
    Joined: Oct 9, 2009
    Posts: 67

    Ironmonger
    Member

    Actually, in my kit is GM positive seals.....I will try to post pix. I will make sure I use the steel shields n o rings, I just want to know if there is a way to use the others.
     
  11. Commish
    Joined: Jan 9, 2010
    Posts: 379

    Commish
    Member
    from NW Ok

    You have got some good advice already, I would add that if the valves were sealing good and you are not going whole hog with a valve job, then leave them alone, lapping them will just make a wider seat, which results in less holding pressure from the springs, and a better chance of burning a valve.
     
  12. I'm almost afraid to ask, but why the decision to tear into the heads? What kind of cranking compression readings were you getting? Did you have a couple of weak cylinders?
     
  13. Ironmonger
    Joined: Oct 9, 2009
    Posts: 67

    Ironmonger
    Member

    Reason. O rings petrified, seats have enough pitting or dimpling from hard carbon to warrant lapping and flute on most of the valves def. needed coke material cleaned off.
     
  14. stimpy
    Joined: Apr 16, 2006
    Posts: 3,547

    stimpy

    the pitting is actually from the lack of lead in the fuel , the lead acts as a cushion , lubricant and antiweld , and when its gone the valves will microweld when they get hot as the seats are non hardened ( pontiac induction hardened then starting in 1969 ) and pull the material off and it burns off the valve face ( this is what causes valve recession in the head) . use a lead additive in the fuel . all you need is what the bottle says not more as it doesn't help things but lighten your wallet . the only real way to prevent the pitting is to go with stainless valves and a hardened exhaust seat ,

    as for the positive type seals they will work but after a while they wear out because of the excess clearance the guides have built in them , you do not tighten up this clearance under factory specs unless you want to seize or gall the valve stems , the extra port length on the exhaust keeps more heat in the head and this is why they have the larger clearance in the guide to prevent sticking valves , back before tight emissions it was ok , but after 1975 it helped contribute to the Pontiac engine demise .
     
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  15. Ironmonger
    Joined: Oct 9, 2009
    Posts: 67

    Ironmonger
    Member

    Can I use a lead sub. additive or does it need to be the real tetraethyl. stuff ? :)
     
  16. I just had my machine shop quote me 80.00 for 8 hardened seats installed. No brainier if the heads are off.
    From your valley pan thread, I'm guessing you already have the heads on.
     
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  17. stimpy
    Joined: Apr 16, 2006
    Posts: 3,547

    stimpy

    the lead substitutes in a bottle work , your not going to find any real tetra fuel on the open market , as its use has been outlawed completely as of the early 2000's for taxable fuel , there are some companies that sell it diluted to minimum as a additive and its kind of expensive . the TEl works best , there is a company in Minn that sells some real good stuff since gold eagle discontinued it ( 104 octane ) red line oils sells a real good one too . just to let you know when you use the substitutes some times the plugs will come out orange colored thats from the additives and thats normal .

    but like vic said the best way is hardened valve seats , I like to find his machinist as there 30 a pop plus parts here .
     
  18. Ironmonger
    Joined: Oct 9, 2009
    Posts: 67

    Ironmonger
    Member

    Very helpful. Just curious, isn't Av. fuel still leaded? I will be looking into those substitutes. I will post the before n after of the lapping once I am in D.C. I had to do the lapping for several reasons, most time based, and I am in Elko, NV, look it up......no machine shops cept one and he wanted $260 for a basic valve job. This isn't a race car....lol And I took the time to port match, port the intake n exhaust, etc. I'll post pix. :)
     
  19. Ironmonger
    Joined: Oct 9, 2009
    Posts: 67

    Ironmonger
    Member

    Just getting around to posting pictures of the upgrade and in car clean up job of the 389 in my 1964 Bonneville. Remember, this was about what I could do in house and in time. Work accomplished is the following. New roller timing set, New copper head gasket set, new N.O.S. gasket set, New Melling SPC-7 Cam, New Melling high performance lifters, Royal Purple break in oil. Heads-intake-exhaust gasket matched. Heads very mildly ported, lapped, cleaned and new seals installed. All cadmium parts cleaned, acid etched and dull cleared. Engine compartment reshot after pulling all firewall mounts. Some small weekend stuff still to do when it is warm again like detailing the steering pump, dipstick, add a chrome air GM style air cleaner, etc. The purpose is a nice daily driver not a 100% correct show car. I really appreciated all the advice and help that each and everyone chipped in for me, it was nice to have all the excellent info. on hand as I needed it :) PLEASE SEE MY 1964 Bonneville ALBUM and you will see much more detailed, condensed pics of the job:)
     

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