Big Block Chevy Exhaust Valves Sticking

Discussion in 'InsideTopAlcohol.com Tech Questions' started by Ridergary, Aug 20, 2019.

  1. Ridergary

    Ridergary New Member

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    Hi, I built a tribute AA/FA circa 1966 with a blown BBC and have been having trouble trying to keep it running on methanol without seizing a few exhaust valves every run. I'm running a .040 over 396 with iron large port heads at about 10 to 1 comp. Roller cam with .600 lift so its not too radical. Currently running a 6-71 non stripped blower at 10% over with a bird catcher and a 110 pump. We removed the valve seals and loosened up the valve guide clearance. This has been happening while only cackling the engine maybe running it 4 or 5 min.
    Is this something common to BBC's if they are run too lean? Only have hat injector nozzles. Running .040 nozzles and a .165 main. Any help would be appreciated...Thanks
     
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  2. OwnBlock

    OwnBlock Member

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    ali heads or steel. if ali what type. some aftermarket heads have cruddy guide material that s/s valves dont like. take oil restricters out if your using these.. how much oil do you run. how big is the sump. look inside rocker cover have you got oil up there.
     
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  3. aj481x

    aj481x Member

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    Try richer idle.
     
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  4. Critical Mass

    Critical Mass Member

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    What do your plugs tell you? What are you using for a barrel valve? What is your boost pressure, etc.
    When you ask a question on this site you need good data or you won't get a good answer.
     
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  5. nitrowannabe

    nitrowannabe Member

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    Bronze guides ?
     
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  6. Ridergary

    Ridergary New Member

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    Yes The Iron Heads have bronze guides. I'm using a K valve and only hat injection. No idea how much boost I'm making but it's 10% over and the blower isn't stripped so it cant be that much. All this occurs basically at idle and blipping the throttle a few times.
     
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  7. oldskooldigger

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    I know it's apples to oranges, but I ran into the exact same issue when I switched from ductile iron guides to bronze on my iron head 392 Chrysler. I opened the guides to .347 (.341 valve stems) figuring it's because of the expansion coefficient difference between iron and bronze, and no more issues.
     
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  8. Ridergary

    Ridergary New Member

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    It looks like the valve guide clearance was the issue along with nozzle and main jet selection. Have run it 3 times with no problem.
     
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