Backfire on 425 Nailhead

Discussion in ''Da Nailhead' started by garys64wildcat, May 30, 2009.

  1. garys64wildcat

    garys64wildcat garys64wildcat

    Doc,Tom and Marc Thanks

    Doc, Do you think that the "cat pee gas" would make it bog down at higher rpm coming up a hill or ? or would the wires to make it do that? I bought the best wires Napa had last yr.. He replaced the gas hose with a fuel inj. hose. I have trusted my Mechanic for 15 years and he knows his stuff so I take him at his word, even though I was P-Oed
    The backfire is gone. Any good way to check the plug wires w/o changing them. I had a coil wire arcing and burnt though and shorting out when I replaced all. I dont see any arcing now.
    Sure wish I could get 100 plus octane the Cat needs good food.

    I`m quite dumfounded, I can usually figure these things out. I been around cars for many years and I feel like There must be a simple fix. It just finding it.:Dou:

    I`ll even buy the :beers2: Gary
     
  2. wkillgs

    wkillgs Gold Level Contributor

    It does sound like it needs more gas. You can increase the accelerator pump shot by moving the rod to a different hole....on the pump lever on top of the carb, move the rod to a hole closer to the pivot pin.
     
  3. doc

    doc Well-Known Member

    Like Walt, I am assuming a carter carb.... and yep , what Walt said will richen the shot.... and the cruddy gas you get now days can affect running , I just bought some on my trip to Texas that would not run good in my 98 explorer... i would say that there are 3 possibles, Bad gas, weak ign coil, weak fuel pump.... or possibly a restriction in the fuel supply.....causing a lean out condition.....
    Gary, you just have to keep working at eliminating one thing at a time untill you make it run right.... some times these situations are a combination of things....
     
  4. garys64wildcat

    garys64wildcat garys64wildcat

    Doc
    Hope you get the cam bearing figured out. I wish I could help. but its being a few yrs since I changed out a cam.
    I swapped the coil with another and does the same thing. moved the acc. pump 1 notch still same. new NGK plugs. I going to swap out the points set with a new set today. I hope that helps. Ive got bad condenser`s before. and check for any crack wires in dist. etc. checked all new wires. I had a 55 Chev that had a dist lead cracked where in went in the dist. I have our Buick open the 20th and Im going nuts. oh yes fuel pump is doing good. Im about ready to blow a gasket on this:af: You guys are helping me keep from going crazy. Thanks for the effort and taking time to help. I hope I can return the favor someday. I`ll buy the drinks:beers2:And It dont backfire anymore though
    Gary
     
  5. garys64wildcat

    garys64wildcat garys64wildcat

    Help!! :pray: I ready to jump off a high bridge.

    Saturday I changed out the points and condenser(bluestreak) fixed a cracked dist. wire. Runs smooth at low rpm.
    Drove her, added a bottle of octane booster. kicked down on gas, could hear secondary`s cut in. still feels as if something is holding her back. revs fine in nuetral dont backfire just dont run properly at high rpm under load. flat ground or up a hill
    I down to replacing the plug wires, I dont know if a fuel pump would cause this :Do No:. Mech said it was good. It feels like a bad plug or wires but they are new. Its probably something simple but its driving me:rant: nuts
    Gary
     
  6. wkillgs

    wkillgs Gold Level Contributor

    Gary, I once had a problem where my car just felt lazy. Turned out to be a corroded terminal on the coil wire. I suppose you could test all your plug wires with an ohmmeter to see if one is bad.
    Try the coil wire first. make sure all contacts are clean.

    Have you checked your spark plugs lately? fouled?

    Another possibility is 'a piece of rubber hose' is stuck in one of the carb passages or jets and causing a lean condition.
    The easiest test would be to swap on a different carb for a test run.
     
  7. Schurkey

    Schurkey Silver Level contributor

    What is your fuel pressure WHEN THE ENGINE IS UNDER LOAD?
     
  8. garys64wildcat

    garys64wildcat garys64wildcat

    Thanks Walt
    I swapped out coils and new coil wire. Plugs are not fouled, wire brushed all leads. Need to test wires with ohm meter, got to get new one mine went TU. I dont have a spare AFB laying around to test. I going to retime. If its in the Carb. I paid the Mechanic to rebuild. it goes back. I thought of distributer if high speed advance is working. It moves freely but? I`ll be so happy when it works again. I put new wires last year under 1000 miles on them.
     
  9. Schurkey

    Schurkey Silver Level contributor

    What is your fuel pressure WHEN THE ENGINE IS UNDER LOAD?
     
  10. garys64wildcat

    garys64wildcat garys64wildcat

    I dont know, the mechanic said it was good. I have a lot of things I`m going to have him check that I cant do at home. I getting tired of asking for help.
    Thanks
     
  11. telriv

    telriv Founders Club Member

    Gary, don't forget that small piece of rubber that caused the carb. to flood over in the 1st place???? Could be some got through & is now partially plugging a jet. At this point, since you have tried most everything else, my advice would be to start at the source. Use the KISS principal as John said. I use this as a 1st. in all I do. Don't forget these cars are over 40+yrs. old now. Run the car till the tank is almost empty. Drop the tank & pull the sending unit & check the "Sock". New ones are available from GM still. I have the part number at work. Replace the rubber hose from the tank to the frame line with the new fuel injection hose. My car did somewhat the same on the drag strip where it lost the top end. Turned out the original rubber hose had a small crack in the top & would suck air which in turn starved the engine for fuel on the top. Never leaked a drop of fuel because it was higher than a full tank of fuel. 40+ years on rubber is a LONG time. Replace the hose that goes from the rocker to the pump with the same hose. Replace the hose from the pump to the filter with the same fuel injection hose. After you have done this report back. Almost sure the problem will be solved.
    Then we can attack the MPG problem. One step at a time. It is probably a multiple of little things.
     
  12. garys64wildcat

    garys64wildcat garys64wildcat

    Tom
    You are probally right. I thought of something in the tank. or plugged or cracked line but never put 2 and 2 together since it runs perfect til I step on it. Gary
     
  13. doc

    doc Well-Known Member

    some times a fuel pump will pump enough at low speed and not enough at high speed...... have you changed anything else????? I recently had a problem similar and discovered 2 things, the ''new'' fuel filter was restricted and there was a dirt dauber nest in the fuel line......also ck the gas tank cap for proper venting....
     
  14. garys64wildcat

    garys64wildcat garys64wildcat

    Guess what!! I found it :TU:

    I went over the line from the gas tank and I found a spot that the previous owner had spliced into the line. There was a cracked hose in the part he had fixed and I could see a small wet spot. I replaced that section and she now runs great.

    I noticed that the guy had stuck a piece of 1/4 copper tubing in and didnt replace the whole hose. But the I/D of the copper is smaller than the i/d of the main line from the tank. That may be restricting the flow to pump. Am I correct to assume that it does. Looks like 5/16 area fuel line from the tank

    I plan to change out the whole hose after I run the tank down to empty. I feel better already that you Guys were there and were kind enough to offer help. I hope to return the favor

    Many Thanks to all and I`ll buy the DRINKS
    :beers2: :beers2:
    Gary
     
  15. telriv

    telriv Founders Club Member

    More than likely the hose size will be 3/8ths.
     
  16. doc

    doc Well-Known Member

    Replace the fuel pump, then you will know that it is good.....
     
  17. garys64wildcat

    garys64wildcat garys64wildcat

    Thanks Doc you guys saved my A@@.
    :TU: Thats my next plan. She runs great except it still has a hesitation at high speed. So I think when I change to gas line hose to be all one size. I`ll do that. Who sells a good one?
    Gary
     

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