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Thread: Please help diagnose 455 olds problem!

  1. #1
    dekmaster
    Hi all,
    I took the 455 olds Rogers out last weekend. I recently got a brandnew BIGS tuned Holley 750 DP on it. And the first part of the day everything was fine; however towards the end this is what happened. As I am getting to higher RPMs like 3500~4500 It seems like the boat is running out of gas. It just stops pulling and sometimes even dies. It's like its having a hard time keeping RPMs up. It fires right back up when I try to start it though. I thought it might not be getting enough fuel because I have a 30 year old fuel pump on it. But now i'm thinking it could be a timing or too much fuel issue. I have a stock distributer on her. I have an hei lying around. I hvaen't put it in yet. If you guys think it is a timing or ignition issue. Can you guys walk me through how to put in the HEI and set the timing up correctly. I really need to get this figured out because I am going to Shasta this weekend. Thanks a million in advance.
    Dennis

  2. #2
    Senior Member
    Join Date
    Feb 2009
    Posts
    2,559
    It's a 455

  3. #3
    Hallett19
    I know exactly what is wrong with it........ its an Oldmobile !!!
    Sounds like it is probably running too rich at higher rpm's, maybe the jets are too big for it. I dont know much about carbs, but this is what is sounds like.
    Check the timing, I would change the fuel pump out too, 30 yr old parts on a boat would make me weary. I had rebuilt my motor, carb , etc and ran the original distributor, even with new electronic pickup in it and that ended up being why my motor ran bad. Keep newer parts on there, its vital to it running good.
    If you can see the tail pipes and its blowing out black smoke at any point, its probably running too rich. If you can, take off the flame arrestor/air cleaner and see at those RPM's if its PUKING fuel into the motor, if so, it could be your problem.
    Maybe post this in Gear Heads, they might have a better idea than these clowns in just jets

  4. #4
    Floored
    Being a Clown with a 455 I would say dump the pump. Also check fuel filters, fuel lines(tight bends or kinks) and water seperator if you have one. Bigs usually hits it good on their carbs, so also look at dwell and timing. total at 32-36. Clown out!!

  5. #5
    bakerjet
    don't sweat the oldsmobile i ran one in an avenger for 10yrs and never had a problem,but it was a 60mph boat and i never turned it over 4700r's. if it was fine the first part of the day then i would check the filter because it does sound like a starvation problem i had the same thing happen when i changed to a bigger carb the 650 was fine but the 750 was to big for the stock fuel pump went to a hi pro and it was fixed. to change dist pull your old one and stab the new one pull the #1 spark plug and hold your finger over the hole while someone bumps the starter when you feel compression thats #1 top dead center (tdc) then pull the cap off the dist. and see where its pointing that is your #1 plug wire then get your firing order and go around your dist. arccordingly hope i didn't confuse you!

  6. #6
    n8dawg
    dump that pump, maybe go with a electric pump with a pressure regulator and a fuel pressure gauge just to keep an eye on things.
    good luck!

  7. #7
    dekmaster
    Why can't I just mark the position of the rotor and just change out the wires exactly as they are?
    Dennis

  8. #8
    bakerjet
    you can. i thought you wanted the full rundown.

  9. #9
    Sleek-Jet
    don't sweat the oldsmobile i ran one in an avenger for 10yrs and never had a problem,but it was a 60mph boat and i never turned it over 4700r's. if it was fine the first part of the day then i would check the filter because it does sound like a starvation problem i had the same thing happen when i changed to a bigger carb the 650 was fine but the 750 was to big for the stock fuel pump went to a hi pro and it was fixed. to change dist pull your old one and stab the new one pull the #1 spark plug and hold your finger over the hole while someone bumps the starter when you feel compression thats #1 top dead center (tdc) then pull the cap off the dist. and see where its pointing that is your #1 plug wire then get your firing order and go around your dist. arccordingly hope i didn't confuse you!
    You'll also need a switched 12 volt wire to the HEI.
    If you're running an old points type distributer, you can use the positive wire to the coil if you find the ballast resistor and remove it. HEI's need a full 12 - 14 volts to run correctly.
    Your tach will also connect directly to the HEI, there is a blade labeled for it, just look on the pan handle of the cap.
    You can also note the rotor position of the old distributer as you pull it out, then put the rotor in the same place when you stab the HEI. Make sure you don't turn the motor if you do this. It's not a big deal, but if the motor is turned, you'll need to find TDC on #1 (as descibed in the other post) and re-stab the distributer.
    Depending on you compression and what not, Modilido's recommends no more than 36* total timming.

  10. #10
    Foggerjet
    Been there, done that. Same excact thing. Draining the bowls. Also a 455. a $59 summit HP fuel pump did the trick. Be careful, a motor leaning out at higher RPM, at full load is a bad thing, Regardless of the manufacturer.
    fog

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