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52 Plymouth Flathead running rough

Discussion in 'The Hokey Ass Message Board' started by vickswhips, Apr 19, 2012.

  1. vickswhips
    Joined: Feb 22, 2006
    Posts: 43

    vickswhips
    Member

    Ok, I have a 52 plymouth flathead 6 that starts as soon as you turn the key and just purs like a kitten. When you rev it up is sounds like its missing a little but nothing real noticeable. However, put it in gear and it has a hard time (rough running as hell) getting going, but once going it runs smooth down the road in all three gears. At 50 mph it drives perfect, it just has a spot in the acceleration where it runs rougher than hell and backfires to if you keep on it. I cleaned (not rebuilt) the carb on it thinking it just need the carb redone and that cleaning it real good may be good enough but it made zero diff. I am a body and paint guy so motors are my weakness but I am trying to learn this stuff since my dad lives to far away and don't have time to drive down here every time i need engine troubleshooting...and he won't be here forever so I need to learn this mechanical part of hot rodding. Any help is appreciated.
     
  2. R Pope
    Joined: Jan 23, 2006
    Posts: 3,309

    R Pope
    Member

    Try retarding the spark a few degrees. Those old sixes don't like much advance.
     
  3. George/Maine
    Joined: Jan 6, 2011
    Posts: 949

    George/Maine
    Member

    If you dare to remove the dist mark rotor were it points.
    I would replace points and condenser check for loose shaft and oil dist.
     
  4. Rusty O'Toole
    Joined: Sep 17, 2006
    Posts: 9,487

    Rusty O'Toole
    Member

    Sounds like ignition breakdown to me. Could be anything from bad plug wires to bad condenser, coil, worn distributor shaft etc.

    How long since you have done a tuneup? Do you know a good engine man who is old enough to remember the old models?
     

  5. R Pope
    Joined: Jan 23, 2006
    Posts: 3,309

    R Pope
    Member

    If retarding the spark doesn't work, it probably needs new plugs. Missing under load is almost always plugs.
     
  6. vickswhips
    Joined: Feb 22, 2006
    Posts: 43

    vickswhips
    Member

    I aint scared to to work outside the engine but not good at diagnosis of problems yet. I know what to check for to get one to run but after that it is all guessing and that can get very expensive! I will try the things ya'll have suggested and I appreciate the help. I just bought the car so no real history other than a head gasket was replaced and the mechanic said the pistons looked new in it. He also said something about exhaust valves needing replaced at some point???
     
  7. tjmercury
    Joined: Oct 22, 2010
    Posts: 589

    tjmercury
    Member

    I'd start with a basic tune up (plugs, wires, cap, rotor and maybe points/condenser) just for good measure, after all it could probably use it anyway, then if that doesn't work, then work your way outward from there. Another thing to check is the wire inside the distributor that goes to the points to see if it is chafed. Had this happen on my flat six, and it would run like shit under load then smoothed out when it got up to cruising speed. Damn near pulled my hair out over this one!
     
  8. vickswhips
    Joined: Feb 22, 2006
    Posts: 43

    vickswhips
    Member

    I like it, thats what I will do! Just put a belt on it after throwing it yesterday and resealed the thermo housing cuz it was leaking. She has been sitting for at least a year with only occasional starting and moving around the guys yard.

    Thanks again
     
  9. Ole don
    Joined: Dec 16, 2005
    Posts: 2,915

    Ole don
    Member

    It may be time for a compression check to see if those valves are good. Then spark plugs, points and condenser, then rotor and cap, and finally wires. If one cylinder is low on compression, at warm idle listen at the exhaust pipe for a whooshing sound. You can slowly pour about a quart of clean H2O down the carb at about 2000 to clean some carbon off the valves, but if you have a bad exhaust valve, it has to come apart.
     
  10. honeyman
    Joined: May 24, 2010
    Posts: 330

    honeyman
    Member
    from Steiner

    Hope the plugs aren't rusted into the head...water will collect in the depression around them in the head and if you don't pull 'em every now and then, they'll rust in place. After removing them, use some anti-sieze putting them back in. Distributor on those flat 6s will go in at 180 degrees out, or spot on, best to mark location of rotor as suggested. Definitely start as tjmercury suggests...
     
  11. While you're messing around with the ignition stuff, try to check that the mechanical and vacuum advance in the distributor are working properly; advance weights not sticking, vac advance holding vacuum, etc. Is the vacuum hose to the distributor connected properly? Though off the top of my head I don't know if it should go to manifold or ported vacuum.

    Are you getting an intake or an exhaust backfire?

    If you end up going back to the carb, make sure that the choke is staying fully open once the engine is warmed up. Check that you've got a good accelerator pump shot when you open the throttle from idle. Make sure that the power piston and metering rod is moving freely and not damaged.

    You might try driving it once with the choke maybe half closed. If the driveability improves that would indicate that you're fighting a lean fuel mixture problem. Did you have any little springs or balls left over when you cleaned the carb? :rolleyes:
     
  12. vickswhips
    Joined: Feb 22, 2006
    Posts: 43

    vickswhips
    Member

    It backfire under me so its the exhaust. I just bought a compression gauge set and have been wanting to try that out so what should it read? I found some plugs at auto zone but the distro tune up I only found on ebay for 40 bucks which seams a bit much but if that is normal I am all for it. I just don't want to sink 500 bucks and then find out the damn motor needs rebuilt or something like that. So lets start with compression, whats the numbers? How hard is a valve job? I have worked inside 302 and 350's with my dad yelling at me so I am not knew to this just diagnosing stuff and knowing the numbers, sequences. Is there a manual on these motors? I am wanting to keep it for the kids so they can pick out paint and help sand and fixer up so I want it to be a good driver for around town and such.
     
  13. vickswhips
    Joined: Feb 22, 2006
    Posts: 43

    vickswhips
    Member

    new plug and plug wires helped it a lot! However, when your on the highway and try to go over about 50mph or just floor it it just starts running like crap and backfiring. Son on to some more attempts. I will do compression test to day just to get that out of the way.
     
  14. Ole don
    Joined: Dec 16, 2005
    Posts: 2,915

    Ole don
    Member

    When doing a compression check, the numbers are not as important as them being even. On that motor I would guess 90 would be a good number, with none lower than 78 or so.
     
  15. Westco48
    Joined: Oct 21, 2010
    Posts: 199

    Westco48
    Member

    Welcome to hotroddin!!
     
  16. vickswhips
    Joined: Feb 22, 2006
    Posts: 43

    vickswhips
    Member

    Ok. Complete rebuild of carb, new plugs, plug wires, condenser, points, coil, battery, and compression check on all cylinders showing around 75-80 with my new snap-on gauges. The Distributor is sitting counter clockwise so that the slot that bolts it down is not within the bolts hole. So the lip of the bolt down bracket sits right against the bolt. If you move it to within the slot it runs worse. I tried to move the plugs counter clockwise one slot on the cap so I could advance the distro to the bolt down slot but it will not run like that. Car runs smooth and very nice up until the rpm range of shifting time, which would be fine except when your in third trying to go 50mph and it starts running like total shit. I can not for the life of me figure this out. I have spent a lot of time checking everything and replacing a lot stuff for no change. Anyone have any better ideas? How do you test the vacuum advance because it seems to me that it must be in that mechanism at this point. There is nothing else to try that I can find or think of.
     
  17. How did the distributor cap look? Always look at the wire ends that plug into it as well. If you haven't gotten a cap for it, consider doing so. You may have a bad tower or crack between them internally. That would show up under a load.

    Bob
     
  18. yetiskustoms
    Joined: May 22, 2009
    Posts: 1,930

    yetiskustoms
    Member

    my 54 plymouth was having issues as well. after dumping so much time and money into it there is a time to just throw a SBM in it and be done lol. i am leaning that route. good luck though getting it dialed in!
     
  19. vickswhips
    Joined: Feb 22, 2006
    Posts: 43

    vickswhips
    Member

    I just puled the distro and cleaned the shit out of it. The cap, rotor, condenser, and points are new.

    BUT, when I looked in the vacuum advance deal that screws to the side of the distro you can see where there is like a old deteriorated diaphragm inside that is no longer functioning. I think this is the problem. Is this replaceable or rebuildable? Where does a poor man look for such a thing?
     
  20. vickswhips
    Joined: Feb 22, 2006
    Posts: 43

    vickswhips
    Member

    I am very close to such a conclusion! A few more attempts and I am done with the damn thing for a while. I my 51 ford F1 just a brake bleeding and fuel filter away from drivable.
     
  21. Bad Eye Bill
    Joined: Sep 1, 2010
    Posts: 841

    Bad Eye Bill
    Member
    from NB Canada


    This right here. Have seen this more than once.
     
  22. tiquer
    Joined: Oct 21, 2010
    Posts: 65

    tiquer
    Member

    My fellow canuck is on the right track. Change plugs and she will run great.
     
  23. vickswhips
    Joined: Feb 22, 2006
    Posts: 43

    vickswhips
    Member

    wire is good and plugs are brand spanking new. However, I did notice today after taking it for a long drive that for some reason when you start climbing hills it goes away, the steeper the hill the better she runs under full throttle! But as soon as you top the hill and try to floor it she just start sputtering again. So when I said under a load I guess that was incorrect, its only when not under a serious load and full throttle. Timing is the only thing I have not checked with actual equipment. That is the last thing than can be done. I checked the gap on the points and adjusted them because they were .16 and I read they should be .20 I also gave them a few strokes of fine grit sanding to make them good and clean. When I cleaned the distro today there was some gunk on the rotor shaft that came off. All and all this thing runs really good up until the point of where you should shift gears at, but in third you need the remaining power to do 55mph without it sputtering...which can only be accomplished by climbing a damn hill. Anyone want a Plymouth that is great for just climbing hills I got one.
     
  24. vickswhips
    Joined: Feb 22, 2006
    Posts: 43

    vickswhips
    Member

    Also I have noticed the damn coil seems to be getting way to hot, not sure why this is happening but I know it should not be that damn hot. Its a brand new chromed out Accel Super Stock.
     
  25. do you have a vacuum tester? (MityVac) hook it to the vacuum advance and put some vacuum to it. If it won't hold- replace it.

    If you don't have one, hook a hose to it, long enough you can watch the advance plate and suck on the hose at the same time. Apply vacuum. You'll feel it if it won't hold, and you can see whether the plate moves.

    It makes sense. As you throttle into the hill vacuum drops and advance decreases. When you top the hill and ease off the throttle vacuum increases, need for advance increases, and she stumbles.

    to get one-- ebay or Andy Bernbaum
     
  26. farmergal
    Joined: Nov 28, 2010
    Posts: 2,074

    farmergal
    Member
    from somewhere

    private message my boyfriend here on the HAMB. his name is welded78. We have a '50 plymouth with the flat six in it and we went through all of these EXACT same issues from the very hot boiling coil to the giving it gas and having it gargle. Our problem was the exact same stuff and if you try and drive it anywhere; once it gets hot it will die at any stoplight or stop sign (super fun)! It's very simple fixes and you'll be able to do it so make sure you PM him! He can tell you what he did to fix it. very simple stuff.
     
  27. vickswhips
    Joined: Feb 22, 2006
    Posts: 43

    vickswhips
    Member

    Sent the PM...hope to hear something before I get creative with some explosives.
     
  28. Bad Eye Bill
    Joined: Sep 1, 2010
    Posts: 841

    Bad Eye Bill
    Member
    from NB Canada


    Posting the fix here would help everyone.
     
  29. vickswhips
    Joined: Feb 22, 2006
    Posts: 43

    vickswhips
    Member

    I know when I figure it out I will be posting my finds to save others from this insanity!!!
     

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