401 Nailhead not running smooth

Discussion in ''Da Nailhead' started by RJBT, Dec 19, 2010.

  1. RJBT

    RJBT Well-Known Member

    I have a 60 Electra convertible with a 401 that I cannot seem to make run smoothly.
    I bought it 6 months ago and have changed all oils/filters, put in a Pertronix Ignitor and coil, and changed all plugs.
    When cold it runs a little choppy. When hot it is better but still not very smooth.
    I finally tested the compression yesterday:
    Each side: (Driver) 190-190-195-190, (passenger) 185-190-190-185
    With a teaspoon of motor oil: 200-200-200-195, 195-200-200-195
    Are these OK numbers ?

    Here are the plugs (photos) some are nice and brown and a few are black (one is wet black ?) I am not sure what this all means ?
    Anyone have any insight to share ?

    Attached Files:

  2. SteeveeDee

    SteeveeDee Orange Acres

    The third plug in your left hand is oil-fouled. That'll cause it to run rough. Given the general condition of the other plugs and the good compression, it could just be pumping oil due to a bad plug wire, a bad intake valve seal, something like that. If you dare, run you hands along the plug wires while the car is running, or, less painful, fire it up in the dark and look for arcing to ground along the wires. If they are brittle, toss 'em and put on a new set.
  3. 66electrafied

    66electrafied Just tossing in my nickel's worth

    From what I could see you've got a dead plug there with the black wet one. Try a new plug and see what happens. From the looks of it that may be your problem. The compression numbers aren't bad; in fact they're pretty good. From the larger picture I can see that your carb might be in need of attention, it looks like it's weeped and seeped all over the place, and might have a vacuum leak. Those carbs were also susceptible to corrosion on the base if that steel plate wasn't used, and I've seen many a vintage AFB destroyed as a result.

    It also looks like your vacuum advance may not be hooked up or is running off the wrong port. It should be connected to that port on the front passenger's side of the carb under the fuel line, - there's either a plug there or a busted hose, can't be sure because the picture is pretty grainy. If this port is actually open, - there's your vacuum leak, and hopefully problem solved.

    So, for starters, replace the plugs, and if it doesn't run any better, go to the fuel system. Check for vacuum leaks first, buy yourself a good vacuum gauge and read up on how to read and interpret it. This can tell you more of what's going on in your engine than a compression tester can.

    How old is that engine? Is it the original, meaning untouched or has it been rebuilt along the way? I've seen older un-rebuilt nails develop vacuum leaks on the intake manifold gaskets when they actually rust away, or in the carb base as mentioned above.

    Hope this helps...
  4. doc

    doc Well-Known Member

    put in a set of autolite 85's gapped to .035 and ck the dist cap and rotor for cracks and/or carbon tracks.... replace with a cap and rotor that has brass terminals not alluminum.... make sure the spark plug wires are good.... and ck the carb real close,,,, heck,,, just rebuild it..... it looks like you have some fuel leak problems any way...... ck the air cleaner filter element.... from the looks of the plugs the engine is running rich... and fouling out the plugs.... with the engine fully warmed up set the idle mixture with a vac gage.... to the highest vacume.... set the timing up on 8 deg with the vacume advance disconected... yeah, i know that the factory says 2 deg... but they were lighting real gasoline back those days , not the cat pee we get now days.... it takes more lead to make the cyl fire now....
  5. RJBT

    RJBT Well-Known Member

    Thanks for the responses !
    Additional detail:
    I dismantled my distributor while putting the pertonix and changed the vacuum advance thingy.
    I also put a new cap, rotor and plug wires (I tested the old ones and 2 were bad - and it still ran. Actually it cant tell if it runs that much better now... maybe a little....???).
    So everything is new ! New gas filter too (it has a electric fuel pump by last PO).
    I took off the carb and there is a metal (thin and perforated) gasket with gasket material on it (half shredded away). So I put thick cardboard gasket material over it.
    Other than that there is no thick metal spacer. Should there be something thicker and metallic ?

    66electrafied you are right. These are old pictures and the vacuum advance was hooked up to the manifold and not the carb so I changed that a few months ago. Here are a few pics.

    I have old pictures of my plugs when I got the car and the wet fouled plug was fouled then too. Also all plugs are not quite the same color. Why is the combustion different in cylinders ?
    The distributor advance for an automatic 401 for 1960 is 12degrees which is what it was set at and I reset it. Should I change that ?

    I have bought a carb rebuild kit (and will do that this winter) with a base gasket (not metal though - a hard foam type).

    I have no vacuum gauge. I can buy one but am not sure where/what/how to take measurements ?

    I am a bit confused on why there would be oil in the wet plug cylinder. Is that oil or badly burnt fuel on the plug ? Why would oil be in the cylinder ? One small thing to know is that the valve cover breathers always smoke a bit. i was told that was normal on nailheads....

    Attached Files:

  6. telriv

    telriv Well-Known Member

    The problem you are having is very common with the AFB carbs. The metal plate is gone & exhaust is getting into the intake mixture. The base of the carb. is pretty well eaten up from the exhaust. Plug the holes for the exhaust in the manifold. End of that problem & no more metal plate needed. Then you will have to fix the eaten up aluminum on the base of the carb.
  7. doc

    doc Well-Known Member

    The intake is good ,,,,, just replace the metal shield that goes under the carb, like the factory says it is supposed to have..... but I am afraid the carb is toast.... you cant run the engine without a shield under the carb... this is the result...that is the easiest thing to do......
  8. RJBT

    RJBT Well-Known Member

    I am trying to understand the comments about the carb base.
    I don't think it is damaged, what is there is the tar stuck from the base gasket. I did not take it off because I did not have a replacement gasket at the time. But I think the aluminum underneath it (base of carb) is immaculate (unless I am mistaken).
    I now have replacement parts and will take off the carb to rebuild it. What should I check for ? Eaten up aluminum base ? Anything else ?
    Why would my carb be toast ?

    I found this carb plate on CARS. But it does not have a separation wall between the bodies throats (leak between throats - no four holes/throats - bad ?). As for the gasket, this is the type I bought.
    I can see that the base plate blocks the exhaust holes on the intake manifold. Why is that ? I thought the exhaust was supposed to heat up the carb (thus flow gases through the carb ... no ?).

    Attached Files:

  9. doc

    doc Well-Known Member

    OOOOK,,,, time for ole Doc to back up here,,,, I went back and took a second look at the carb base and I think you are probably right .... I looked at it but not closely....upon a close look, it indeed appears that the dark stuff is gasket material.... clean all that off and if the base is not rotten then rebuild the carb.... if it is rotten then it is toast....unless you want to devcon it or some tig work to repair the damage.....when a carb gets corroded bad it is easier to find another carb to rebuild than go to the expense of welding/machineing ect....
  10. nailheadnut

    nailheadnut Riviera addict

    The exhaust gasses are supposed to heat up the carb base, but the gasses are corrosive to aluminum. (If the car would have been equipped with a Rochester 4GC carb with a steel base, the steel gasket would not have been necessary.) The stainless steel gasket makes contact with the carb base and transfers the heat from the exhaust gasses to the carb base, BUT the stainless also protects the aluminum carb base from corrosion. The gaskets you show in the picture are correct; it's not necessary to have dividers in the steel gasket.

    Scrape the base of the carb and look at it closely to see if there is any corrosion.

    The base plate of the carb doesn't block the gasses; they move through the small horseshoe in the intake manifold.
  11. RJBT

    RJBT Well-Known Member

    OK I understand. The steel plate needs to be in contact w the carb base to heat it (and prevent aluminum corrosion). I am in Europe and it never gets really cold here (well I take that back. I meant at least when I take the boat out!!). I will though look to buy a plate anyway to keep the gases from entering the carb (might be my running issue).
    But how do I prevent vacuum leaks between the plate and the carb if there is no gasket ? Metal to aluminum would potentially leak w/o a gasket ..no ?
    Also I feel funny about putting a gasket sealing all 4 throats and then a metal plate that has no seal between the 4 throats (wouldnt there be leaks between throats ? (is that a bad thing or not really ?).
  12. RJBT

    RJBT Well-Known Member

    So as I rebuild my carburetor... and I get the to the heat passages in the intake manifold, which should I best do ?
    • To block the heat rise passage
    • to put a metal plate between carb and intake
    I plan on taking the valley pan off and maybe even the rocker assembly (its quite dirty - wish to clean it inside the rocker arm) so I can gauge the look of all the hydraulic lifters / push rods. If I have good compression does that mean nothing can be wrong with my hydraulic lifters / push rods and I should not touch anything ?
  13. CameoInvicta

    CameoInvicta Well-Known Member

    Which Pertronix setup are you running? Some of them require the bypass of the factory resistance wire - was this done during the install?
  14. RJBT

    RJBT Well-Known Member

    Andy... good point.
    I put in the basic Pertronix (Ignitor I) w the flamethrower coil... I had read there was less than 12V at the lead (resistance) so i tested it (motor not running) and there was 12V ... So I ran it like that for a few days (no problem) and then I decided to test the voltage w the motor running.... gaaasp !!! there was less than 12v (I forget... 7v or something). At startup there is a bypass (had not read all the manual !!)... I tried to look for a resistance and could not find one so i ran a lead from the dashboard to the coil. Do you know where is that damn resistance (or what it looks like) ?
    I did not feel it running any better. Is that for reliability reasons to give it 12v ?
  15. Lucy Fair

    Lucy Fair Nailheadlova

    Resistor wire should go from from ignition lock to firewall,inside car,its easy to find it among other wires.This one is wraped in cotton not in plastic insulation.
  16. RJBT

    RJBT Well-Known Member

    OK I'll look for it. By the way what does the resistor look like ? or is it not visible and wrapped in the cloth ?
  17. doc

    doc Well-Known Member

    The reason of the voltage being higher in start position is so there will be plenty of voltage to fire the system during cold weather.... and ..... the resister wire has a different ''feel'' to it... it is softer and more rubbery than the other wires because it has a different kind of wire center and a different kind of insulation....
    On my 1965 skylark GS chart it shows to be yellow and runs from the #8 terminal of the rt. hand thru firewall connection to the starter solenoid....
    The reason the voltage was cut to 9 volts by the resister wire is to keep from burning the coil and the points up.....
    The old drag racers trick to get more fire to the plugs was to put a straight connection from the battery to the coil, by passing the resister wire thru a on dash toggle switch.... and then another toggle switch to kill the field on the alternator,,, ect.....:Brow: :Brow:
  18. CameoInvicta

    CameoInvicta Well-Known Member

    According to Pertronix, the Ignitor's operating voltage is 8V-16V. Since the resistance wire was not bypassed, that could be the problem, or contributing to it.

    I can only comment on how it's setup on my '62. The wire that goes to the positive side of the coil, is, in fact, the resistance wire. It goes thru the firewall and back to the ignition switch. What I did to bypass it, is just use a normal 4 pin relay. I used the factory resistance wire as the trigger, and then ran a wire from the positive terminal on the battery to the relay, and obviously a wire from the output on the relay to the coil.

    And I did actually try running my setup with the resistance wire in place, and it ran like crap. I have the Ignitor III rather than the Ignitor, but because it didn't have full voltage, it ran REALLY rough, and kinda sounded like it had a big cam in it. Setup the relay, and it ran like a champ.

    Before you go running around fixing all the other things mentioned, I'd fix this first.
  19. gsgtx

    gsgtx Silver Level contributor

    the pertronix I needs the resister wire in place and use there flamethrower I coil or the stock coil,you should only have about 6v at the coil. the pertronix 2 or III does not need the resister wire with there flamethrower 2 coil.
  20. RJBT

    RJBT Well-Known Member

    Actually I thought I read if you have the flamethrower coil you need to bypass the resistor ?

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