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Technical Looking for flathead troubleshooting knowledge

Discussion in 'The Hokey Ass Message Board' started by Thunder Road, Jul 28, 2023.

  1. Thunder Road
    Joined: Sep 17, 2006
    Posts: 164

    Thunder Road
    Member

    Y’all, I am puzzled, My little hot rod has “issues” and I need some extra knowledge and suggestions.
    First, the details of what I have:

    1934 Ford 5-window coupe – my dad bought it in 1958 and sold it to me in 2001 for a dollar.
    Engine = 1936 Ford flathead
    .060” overbore.
    3 / 4 race cam
    Aluminum flywheel
    Eddie Meyer finned heads
    Fenton open plenum aluminum intake for 2 carbs
    2- Ford 94 2 barrel carbs w/#50 jets and idle mixture screws at .75 out.
    Mallory Dual point crab-style distributor- 2002 - 2010
    Accel Hi-Temp Super Stock radio suppression core 8mm yellow plug wires- 2003
    Stock exhaust manifolds
    2003 Walker radiator with Cooling Components electric fan/shroud
    12v system

    Current status- it idles just fine. I can drop the rpm so low that you can almost count the cylinder explosions. I took it out for its first road test since replacing all wheel cylinders and the master cylinder and converting to DOT 5 brake fluid; and replacing the gas tank.

    It started down the road fine- hitting on all cylinders, but then it started to miss a hit or two, then it missed a few hits, then it would run ok for a piece, then go back to multiple-misses. Made it to the non-ethanol gas station and filled her up.

    Left there and the same scenario happened again, when I pulled away from the station, it was hitting on all 8 and then the missing started again- extremely random- HIGHLY annoying.

    So, I am looking for knowledge and experience to tell me: How would YOU go about finding out why it is randomly mis-firing under load?

    Any and ALL suggestions would be greatly appreciated.

    Tom
     
  2. tubman
    Joined: May 16, 2007
    Posts: 6,809

    tubman
    ALLIANCE MEMBER

    If you haven't already changed out the coil and condenser, it would be the first thing to do. Also, you should know that new condensers being "bad out of the box" is not uncommon these days; you may have to try several. The best place to get a coil is from "Skip" Haney in Florida. He rebuilds them with new internals and they are bullet-proof.
     
  3. alchemy
    Joined: Sep 27, 2002
    Posts: 19,997

    alchemy
    Member

    I just replaced a set of plug wires on my flathead to make it run much better. It’s an easy and cheap thing to try. Yours are 20 years old already.

    Also, those Mallory’s of that era were notorious for being curved fine for a small block Chevy, but not for a flathead. Was yours reworked?
     
  4. tubman
    Joined: May 16, 2007
    Posts: 6,809

    tubman
    ALLIANCE MEMBER

    Oh yeah, like they said on "The Ford Barn". the Accel yellow wires could also be suspect.

    Plus they're ugly and unsuited to a traditional vehicle.

    "Alchemy", I think the SBC curve problem is with the later Mallory 8BA distributors, not the earlier ones. Plus, I don't think an improper curve would cause the kind of problem the O/P is experiencing.
     
    caprockfabshop likes this.

  5. Glenn Thoreson
    Joined: Aug 13, 2010
    Posts: 870

    Glenn Thoreson
    Member
    from SW Wyoming

    Have you checked and/or replaced the points? In the dark, check your plug wires for cross firing. Leaking insulation is usually easily seen in the dark. A light show, so to speak. Check for any corrosion in distributor connections and plug wire ends. Check the caps and rotor for tiny cracks or carbon tracking. If the wires run through the original tubes, it requires more work to get them out to check for leakage to each other or to ground. Those wire tubes were not the best engineering feat.
     
    03GMCSonoma likes this.
  6. Bearing Burner
    Joined: Mar 2, 2009
    Posts: 1,102

    Bearing Burner
    Member
    from W. MA

    How long since you last ran it previous to this last run. Could you have water in the gas or old gas?
     
    clem likes this.
  7. Hemi Joel
    Joined: May 4, 2007
    Posts: 1,470

    Hemi Joel
    Member
    from Minnesota

    There's a lot of things that can cause it. Missing under load could be an indication of valve lash too tight, or a burned valve. If the simple stuff checks out good, I would pull the intake manifold and check the valve lash.
     
  8. Ya, check out the ignition first. Maybe get some non-yellow wires :) If it turns out going thru the ignition doesn't help it could be, if the engine sat for an extended time period, the valves may be wanting to stick in the guides. Some marvel mystery oil in the gas and the oil might help cure that, and then regular driving.
     
  9. Thunder Road
    Joined: Sep 17, 2006
    Posts: 164

    Thunder Road
    Member

    tubman- I have a spare coil/condensor. I will swap them tomorrow and see if anything changes
    bearing burner- it had been about 3 years since she was on the street and much of that time was because I was replacing the gas tank- so no bad gas in here at all.
     
  10. jaracer
    Joined: Oct 4, 2008
    Posts: 2,286

    jaracer
    Member

    So far people have mentioned things that could cause your problems. You could start throwing parts at it not knowing if the old parts were good or bad. I'd find someone with an ignition scope who knows how to run it. You can either find any ignition problems or eliminate the ignition system in a manner of minutes. Your problem does sound like it may be ignition related.
     
  11. clem
    Joined: Dec 20, 2006
    Posts: 4,089

    clem
    Member

    If none of the obvious electrical issues above don’t help.

    consider looking into fuel delivery.
    ie, blocked fuel lines or carburettor related fuel restrictions….………
    .
     
  12. Petejoe
    Joined: Nov 27, 2002
    Posts: 12,143

    Petejoe
    ALLIANCE MEMBER
    from Zoar, Ohio

    We would love to see some. Pictures of your coupe.
     
  13. Budget36
    Joined: Nov 29, 2014
    Posts: 12,758

    Budget36
    Member

    Might be tough to find a place with an ignition scope these days. But maybe pull the cap, get a peek inside. Take a look at the plug wire connectors, shine a light inside the female of the cap, look for things that aren’t shiny.
    Fuel issues, just in my experience, don’t start of fine and then randomly get worse.
    Now, I’m not saying a fuel issue won’t do that, but seems to me something in the ignition is breaking down with heat.

    And yes, go ahead and put up some pics, Ryan won’t ban ya!
     
    03GMCSonoma likes this.
  14. Slight left turn here but Tubman how does one contact ‘skip’ Haney about a rebuilt coil?

    thanks,

    mik
     
  15. Lost in the Fifties
    Joined: Feb 25, 2010
    Posts: 456

    Lost in the Fifties
    Member

    Today's spark plugs don't like fuel with lead. If you use a higher octane fuel or booster, I would change plugs first thing.
     
  16. PackardV8
    Joined: Jun 7, 2007
    Posts: 1,105

    PackardV8
    Member

    All the above is good advice.

    When I'm asked to troubleshoot any old car problem, I always say, "Bring it to me with new spark plugs, plug wires, distributor cap, rotor, points, condensor and coil and a fresh tank of gas and a new fuel filter." Nine times out of ten I never see the car. The new ignition parts and/or new fuel fixed the problem.

    Once a guy argued with me, "Yeah, the parts are old, but I don't put more than a thousand miles a summer, so they should still be fine." I told him to try someone else to help him find the problem.

    jack vines
     
    Last edited: Jul 29, 2023
    RICH B, jimmy six, RodStRace and 2 others like this.
  17. jaracer
    Joined: Oct 4, 2008
    Posts: 2,286

    jaracer
    Member

    Actually, any good diagnostician working on modern cars probably has a digital scope. They are great for monitoring electronic sensors and ECM signals. The digital scopes can also be connected to a point ignition system to monitor it's vitals.
     
    Budget36 likes this.
  18. tubman
    Joined: May 16, 2007
    Posts: 6,809

    tubman
    ALLIANCE MEMBER

    Try this link : https://skipscoilsandpumps.com/contact-us.

    BTW, you couldn't do any better than to accept the offer Michael Driskill (@35fordTN ) made you on the "Barn".
     
    rusty valley likes this.
  19. Hotrodmyk
    Joined: Jan 7, 2011
    Posts: 2,283

    Hotrodmyk
    ALLIANCE MEMBER
    1. Northwest HAMBers

    Just went through the same scenario with my friend's 49 Merc. (255 flathead) Similar age on last tune. Here's what we found. BTW the distributer cap was worse.

    badcoil2.jpg
     
    Desoto291Hemi likes this.
  20. Thunder Road
    Joined: Sep 17, 2006
    Posts: 164

    Thunder Road
    Member

    7.29.2023 Update.

    Ok, so I changed out the coil and the condenser. I know these units are good.

    Engine starts just fine and idles good.

    I drove it out onto the road and at low rpm it is nice and smooth. As engine rpm increases, the random misses showed up…much more concentrated than the other day. It was really bad…but it would smooth out some also….


    So, with thanks to you folks, I have decided to go ahead and bite the bullet and pull the grille and radiator off; get new wires, new plugs, and new dist cap, a new rotor and change all of this out. I will freshen up the point contacts and reset them to .016.

    The only thing that makes this an easier decision is that I have found a coolant trail down the outside front of the radiator, so she is in need of repair and I can get that done at the same time.


    Thank you all for your thoughts – they are appreciated…when I get the work done, I will return with another update. I have a special event in mid-September that is a 100 mile poker run for Habitat for Humanity and I want to take the coupe on it…that’s my goal.
     
  21. alchemy
    Joined: Sep 27, 2002
    Posts: 19,997

    alchemy
    Member

    Just so you know, the crab style distributor is the easiest to work on because it comes right off with just a couple bolts. Do the work on the bench, then it bolts back on in the exact same timing because of the offset tang. Other than your leak, there’s no reason to remove anything else.
     
    Desoto291Hemi likes this.
  22. RodStRace
    Joined: Dec 7, 2007
    Posts: 3,300

    RodStRace
    Member

    Since your stated goal is not to just fix the miss but to do a 100 mile run, I'd suggest doing a full tuneup. Check compression, adjust valves, replace wear items (plugs, points, condenser, filters, and those crappy wires) check fuel pressure and volume, inspect distributor wear and advance. Then move on to a full lube and chassis inspection and full brake inspection and adjustment. Make sure you have good rubber and straight wheels. make sure the battery, starter and charging system work right. Make sure the cooling system can handle running for extended periods. Fix any suspect issues and carry tools, fluids and spares. The car currently is not ready for going to the local station without problems, so it will need all of this to go on the run unless you have a friend with a truck and trailer following you. That may sound harsh, but it is going to need more than just fixing the first problem that is current.
     
  23. Thunder Road
    Joined: Sep 17, 2006
    Posts: 164

    Thunder Road
    Member

    Understood RodStRace. You are absolutely correct- I have lots to do.
    Just finished replacing all wheel cylinders and the master cylinder- converted system to DOT 5.
    Car's electrical system is top notch. Full rewire back in 2009.
    Why doesn't anyone like my yellow wires? :)
     
    RodStRace likes this.
  24. Blues4U
    Joined: Oct 1, 2015
    Posts: 7,590

    Blues4U
    Member
    from So Cal

    The symptoms sound more fuel related to me, the engine runs fine until it's put under a load and after some time, as if it's running low. When was the fuel filter changed last?
     
    Desoto291Hemi likes this.
  25. RodStRace
    Joined: Dec 7, 2007
    Posts: 3,300

    RodStRace
    Member

    Glad to hear. I succumbed to the flash of those wires when I built my first engine.
    Had nothing but problems, and one night I popped the hood with it running. Yikes, but the sparks were jumping everywhere! Also turned wrenches professionally for years. Never saw a set that didn't have some issue.
    For an idea of a model A trip checklist(I know, different engine), Paul Shinn just came out with a video.


    Blues, I agree, fuel sounds more likely, but every part of the system (or at least delivery) needs to be checked. A 30 year old car could be just a filter, but a 90 year old car needs every part inspected. Tank, cap, sock, lines, pump and eccentric.
     
    Blues4U likes this.
  26. Glenn Thoreson
    Joined: Aug 13, 2010
    Posts: 870

    Glenn Thoreson
    Member
    from SW Wyoming

    A lot of folks don't realize that plugs can look good but they can begin failing under the pressures of high RPM driving. We used to have a Champion spark plug tester that tested the plugs under pressures up to 100 PSI. You would not believe the number of good looking plus that stopped firing at even less than 100 PSI. The tester had a mirror under the plug and a glass, so you could easily see whether a plug was firing, skipping a beat or whatever. If you do a lot of tune up work, you may want to keep an eye out for one of these. Fuel delivery is easy to check with a vacuum/pressure gauge and a tin can. The pressure and vacuum should be close to spec at cranking speed with all plugs removed. Pull the coil wire and disconnect the line at the carb and have a helper put the end in a tin can and keep it there while you spin the engine over. Spark plugs out, remember. If you get a good strong squirt, it should produce ample volume. If the squirt looks weak or just dribbles, check the pump push rod for length and wear. Lengths for new rods are usually shown with the catalog listings. There are several lengths. Macs Auto parts should have it. If the rod checks out, look down to see the cam lobe. If it looks rough, worn or has very little lift or almost none you will need to replace the cam or go to an electric pump.
     
    RodStRace likes this.
  27. Thunder Road
    Joined: Sep 17, 2006
    Posts: 164

    Thunder Road
    Member

    Long story short- I bought a new tank from Drake in 2006- never ran blended fuel in it and 2 years ago it started sending rust sediment into my filter on the pump. It was nasty. Ripped out the 15 yr old tank and replaced it with a plastic tank. Cleared all of the fuel line and installed 2 see through 'pre-filters' ahead of the fuel pump bowl. The pre-filters are nice and clean and so is the bowl filter. They were cleaned last year and show no sign of any rust particles.
    If you know, what fuel pressure should I expect from a stock pump?
     
  28. Fortunateson
    Joined: Apr 30, 2012
    Posts: 5,177

    Fortunateson
    Member

    This will be very educational...
     
  29. clem
    Joined: Dec 20, 2006
    Posts: 4,089

    clem
    Member

    Those carbs like 2&1/2 to 3&1/2 lbs.
    I set mine at 3 lbs

    Google search came up with this, -

    “Flathead Ford stock fuel pump pressure is 3-1/2 Psi. The fuel pump pressure can be adjusted by adding or subtracting fuel pump stand gaskets.”

    Others on here will correct this if it out by a little……
    .
     
  30. Thunder Road
    Joined: Sep 17, 2006
    Posts: 164

    Thunder Road
    Member

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