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Pontiac Motor Questions

Discussion in 'Other Rides' started by Big'nBadK5, Apr 22, 2003.

  1. Big'nBadK5

    Big'nBadK5 Registered Member

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    I broke out the firebird for the spring today (hasent been driven in 2.5 years /forums/images/graemlins/eek.gif) and was riding around town, i immediatley noticed a sever hesitation and subsequent backfiring/forums/images/graemlins/shocked.gif so i changed the plugs out for a set of #2 ac-delco rapidfire plugs and advanced the timing from 12 to 14 degrees and went out again, while the syptoms did reduce it still did hesitate and backfire. so i went to 16 degrees, and now the hesitation is almost gone but at high RPMs it backfires. not a single loud pop but many smaller pops that rob the power out from under my foot, i was just wondering if i am on the right track and what kind of an advance it is safe to go with. /forums/images/graemlins/confused.gif The motor is a 1977 350 block stroked up to 386 cubes roller rockers and a mallory unilite distributor and powermaster coil. thanks for the help. anything is appreciated.
     
  2. Blaze

    Blaze 1/2 ton status

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    A 77 350? I thought they stopped making Pontiac 350 (354)s in 1975? Or maybe that was just in the Firebird....

    My 79 Trans Am did the exact same thing, except it overheated as well. Turns out the distributor was loose, timing was maxed out, all the vacuum hoses were shot, and the carb needed a rebuild. I'd put my money on a vacuum hose, we fixed everything but the hoses first and it still backfired, but once we rerouted and replaced the vacuum tubing, it ran fine. Sounds like a sweet car, got any pictures of it? /forums/images/graemlins/thumb.gif
     
  3. Thunder

    Thunder 3/4 ton status

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    If the ign is ok. I would look seriously at the carb. Sounds like it may be running lean to me. Maby after sitting all that time the jets are clogged with varinish or the gaskets are dried/rotted out, The accelerator pump may not be working right. Carb may need a rebuild.
    Check Vacume lines too.
     
  4. Hossbaby50

    Hossbaby50 3/4 ton status

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    You might PM DesertDueler. He is a cert. mechanic, and one of his passions is Pontiac V8's. He has a sweet Firebird that has 350 in it.
     
  5. Grim-Reaper

    Grim-Reaper 3/4 ton status Author

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    [ QUOTE ]
    I broke out the firebird for the spring today (hasent been driven in 2.5 years /forums/images/graemlins/eek.gif) and was riding around town, i immediatley noticed a sever hesitation and subsequent backfiring/forums/images/graemlins/shocked.gif so i changed the plugs out for a set of #2 ac-delco rapidfire plugs and advanced the timing from 12 to 14 degrees and went out again, while the syptoms did reduce it still did hesitate and backfire. so i went to 16 degrees, and now the hesitation is almost gone but at high RPMs it backfires. not a single loud pop but many smaller pops that rob the power out from under my foot, i was just wondering if i am on the right track and what kind of an advance it is safe to go with. /forums/images/graemlins/confused.gif The motor is a 1977 350 block stroked up to 386 cubes roller rockers and a mallory unilite distributor and powermaster coil. thanks for the help. anything is appreciated.

    [/ QUOTE ]
    Does it still have 2.5 year old stale gas in it?
    Get some super in it and put some octane boost int it as well as some line dry. Old gas is BAD news. I'm going those serg problems on my 88 Sub because it has only had 1,000 miles put on it in the last 14 months. 40 gallon gas tank. Finnaly got most of it run through it and it's getting better.
     

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