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Technical 235 backfiring and dying off

Discussion in 'The Hokey Ass Message Board' started by 4doorsformorewhores, Jul 17, 2021.

  1. 4doorsformorewhores
    Joined: Jul 7, 2021
    Posts: 61

    4doorsformorewhores
    Member

    Hey y’all, my first post so I’m new here. Bare with me, as my mechanical experience is slim, to none. Anyway here’s what happened to me tonight

    cruised my 54’ bel air about 20 miles on the freeway to a nearby cruise night tonight. As I was taking the exit for my stop I let off the gas and coasted downhill to a stop. After about 5-10 seconds of letting my foot off the gas and I a large loud backfire, and then a second a few seconds later. While coming close to a slow roll at this point as I was getting closer to my stop it died off. Let it sit a second and fired it back up, made it about a mile from there to my destination and it died off again while I was “slow rolling” into the parking lot. It ran OK around town after that, and then when getting on the freeway to come home it started bucking as I was picking up speed, and finally smoothed out. Ran the 20 miles home ok again, and then died at a red light just before my house. Fired back up and drove the few blocks home. A buddy of mine said it sounds like it leaning out, could be the carb float or needle. I’ve frequented the forum here and silently gained knowledge from y’all, so I figured I’d try my luck here. Any ideas is greatly appreciated!
     
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  2. MAD MIKE
    Joined: Aug 1, 2009
    Posts: 626

    MAD MIKE
    Member
    from 94577

    Was it really a backfire(under the hood/through the carb) or was it a misfire out the exhaust?
    Under hood backfire is usually more related to timing being way off, a couple of crossed up ignition wires, or worn spark plug wires inducing spark into another spark plug wire.
    Retarded ignition and rich running will cause a misfire out the exhaust.
    What condition is the Blue Flame in?
    Has it had a tuneup recently?
    Checked the timing? Is the Octane screw on the distributor adjusted correctly?
    What was the last thing done?
    Any modifications to the engine?
    If you just pulled the car out of mothball and put fuel in it and ran it, especially anything with ethanol, most older components and seals don't play well with ethanol fuel. It tends to eat older rubber components and that may be part of the problem.

    Verify the car is in good tune first.
     
    BJR likes this.
  3. 4doorsformorewhores
    Joined: Jul 7, 2021
    Posts: 61

    4doorsformorewhores
    Member

    Not 100% sure on weather it was a misfire or backfire. It was pretty loud, and it did sound as though maybe it came from in front of me. The history on the car is I bought it roughly 6 months ago. When I picked up the guy had photos of the motor had been torn down and rebuilt. Pistons bored .40 over and re ringed, so on and so fourth, but prior to that it sat for 23 years. Said the carb was rebuilt as well. Along with a few other things to make it a driver including new tank, fuel lines, break lines, redone drum breaks, the usual things to get it running. It’s been my daily driver ever since I brought it home, and has ran like a champ since then. I swap points and condenser about 2-3 months ago, checked dwell and timing (as I usually do every so often) about two weeks ago, and that’s about all recently. One thing that has been happening on and off is a random plug wire will pop off after a hard pull on the freeway. That was not the case this time, but it has been somewhat frequent over the past two months. Hope all that info help
     
  4. MAD MIKE
    Joined: Aug 1, 2009
    Posts: 626

    MAD MIKE
    Member
    from 94577

    If you still have the stock air cleaner look for any damage to the housing and that it's not dribbling oil into the intake. Should have a copper mesh kind of element, it doesn't need normal servicing really.
    Doesn't mean it was done right.
    Always verify that everything that was 'done' was actually done correctly. I've picked up 'blown' engined cars for pennies because the PO stabbed the distributor in wrong or the wires were in the wrong order.
    But was it done right?
    Might want to get out a few tools and verify the float and linkage is correct.
    Check the mundane screws/fasteners that are hold items together are also not loose.
    A 'fresh' rebuilt engine still needs a good shakedown even after break-in. Bolts back out, nuts loosen, wire connections are not properly attached, etc etc.
    Any reason you swapped the points/condenser?
    Preventative maintenance?
    Points getting worn?
    Finding good condensers can be hit/miss. Even NAPA parts are turning to junk.
    Wires should clip in snugly and not be easily removed, if they are getting blown off the little tangs are either not bent out enough or lack enough spring tension. Dust boots on the distributor end are merely dust boots. Depending on brand the plug side boots should help seal the wire to the plug. A little bit of di-electric grease on the boot to aid in install/removal and insulation is fine. Either way the metal connectors are what make the connection they should not be loose, do not rely on the boot for retention. If the boot itself is too small it can push off the plug.

    Go over the basics, fix anything that is not right or goofy(wires popping off), and verify the car is in proper tune. Pull plugs, check gap/coloration, go over timing marks, check the fuel bowl has adequate fuel and the carb is set properly. Verify no gasket leaks, air or liquids. Grounds are clean and tight.

    When a car is resurrected like this it needs to be gone over, especially if you did not do the work, and driven to failure a few times to find the weak spots. Whatever you do, don't start throwing parts at it unless the part is known to be verified bad.

    Do you have the service manual for your car?
     
    Last edited: Jul 17, 2021
    Rusty Heaps, squirrel and BJR like this.

  5. squirrel
    Joined: Sep 23, 2004
    Posts: 49,264

    squirrel
    Member

    Make sure the carb does not have any loose screws on it, see if you can wiggle the main body at all. I've seen the screws that hold the bottom throttle body, to the main body, get loose, and cause weird problems.

    The condenser is suspect, those are typical symptoms. I'll repeat what Mike said, they don't make them like they used to. I hope you kept the old one. Buy a couple spares. Look into buying a replacement made using an electronics grade capacitor, I saw where someone on the old chevy truck forum was offering them.

    And yes, make sure the plug wires are tight...
     
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  6. 4doorsformorewhores
    Joined: Jul 7, 2021
    Posts: 61

    4doorsformorewhores
    Member

    so little update on things over the past few days, and to answer some of your questions. By the way I’ll start by saying thank you for the feedback and ideas because lord knows I need all the help I can get with this “learn as I go car”

    so air cleaner in not stock, it’s a 2” element in a chromed top. Everything seems buttoned up well, nothing jumps out as loose or backed out as far as bolts near the carb, or the intake/exhaust manifolds. The points and condenser were swapped because of a whole other story. I “attempted” to go HEI a few months back with a petronix set up that installs into the stock dizzy, after firing it up it had total loss of power and limped home from my buddies after that. So I threw in new points and condenser after that and didn’t worry about it too much, just enjoyed having it back one the road

    after the past two days I checked the dwell with a meter and it reads at maybe 38, a rad high per factory spec, but would that cause symptoms like mine? Timing is SLIGHTLY advanced using a light and the mark on the wheel and notch, but not by much. Swapped the plug wires today and pulled plugs one by one as I made my way down. A bit dry and black, so I’m aware that could be running rich, but again, would this cause the backfire, and dying at low rpms? Today I took it for a spin to feel her out again, has a lot of trouble getting over 2500 rpms, especially in 3rd gear (three on the tree) and just a general loss of power on the top end. Also it gave me a very strange “lunge” or stumble on the freeway after a long gradual turn with Minimal throttle. I guess I’m trying to find a starting point here because I love the 235 when she runs well, but over the past three days every since the little backfire and die episode she’s been feel worse and worse it seem
     
  7. 4doorsformorewhores
    Joined: Jul 7, 2021
    Posts: 61

    4doorsformorewhores
    Member

    carb seems to be tight, no wiggle to the body or anything usual. Plugs are tight now as I changed them out today with a bit of grease on the ends. I did pick up a spare set of points and a condenser yesterday just to have laying around just in case. So if it comes to that I suppose I can try those out and see if we have any better results. Would a bad condenser show symptoms through a loss of power and struggle at top end?
     
  8. HSF
    Joined: Oct 25, 2014
    Posts: 143

    HSF
    Member
    from Lodi CA

    Eliminate one thing at a time. Me personally, I'd start with the carb and fuel delivery in general. Good luck, you'll get it.
     
  9. 4doorsformorewhores
    Joined: Jul 7, 2021
    Posts: 61

    4doorsformorewhores
    Member

    this is the type of encouragement I need right now, because the old chev is currently breaking my heart o_O
     
  10. Budget36
    Joined: Nov 29, 2014
    Posts: 6,713

    Budget36
    Member

    As far as your timing goes…the mark you see is the starting point. A MoToRs manual will tell you to keep advancing it from that point, accelerate in high gear from something like 20mph…I forget the starting point, until the engine pings, the back off a bit. Of course you’ll need to reset the idle. Note you will not see the mark anymore.
     
  11. squirrel
    Joined: Sep 23, 2004
    Posts: 49,264

    squirrel
    Member

    A bad condenser can do different things....that's one of them.

    It's also easy to change, and all of them these days are suspect...
     
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  12. jaracer
    Joined: Oct 4, 2008
    Posts: 1,103

    jaracer
    Member

    In general, backfires out the tailpipe are ignition related. You could have a weak or dying coil also or loose wiring in the ignition. Even a bad ignition switch could cause the ignition to turn on and off creating a tailpipe backfire.
     
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  13. jaracer
    Joined: Oct 4, 2008
    Posts: 1,103

    jaracer
    Member

    I fought a slowly dying coil one time. I swore the engine was running out of fuel. It had a hard time coming up to speed, but would run okay once you attained a cruise speed. It finally died and I had to be towed home. Immediately restarted once I got it home. I took a short ride and it died again, but I was able to restart and coax it home. I have a scope and would get an ignition signal while cranking but a no start most of the time. I had the whole fuel system apart and tested with no problem found. In desperation I bought a new coil and it started and ran fine. I've got an old Sun Coil Tester (small scope with circuitry to energize a coil. The new coil would produce over 30K volts while the old one barely got over 10K.
     
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  14. Tow Truck Tom
    Joined: Jul 3, 2018
    Posts: 141

    Tow Truck Tom
    Member
    from Clayton DE

    Myself, not hearing what you are, I would want to pull the rocker cover and measure the lift or the exhaust valves.
    A worn camshaft lobe on the exhaust side will cause more cylinder pressure than the intake valve can contain. The result is hot gases escape into the intake manifold. This in turn ignites the incoming fuel charge of the intake manifold then up and out through the carburetor. As this takes place there is no fuel available to make power. Good Luck. I would be happy to be wrong.
     
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  15. Tow Truck Tom
    Joined: Jul 3, 2018
    Posts: 141

    Tow Truck Tom
    Member
    from Clayton DE

    As a footnote I should explain, my first 57, 235 needed a valve job. While working on it a veteran mechanic laid a tip on me. He told me that if I would grind the side of the rearmost rocker stand bolt with a flat, it would allow more oil to flow over the top end.
    Well,,,, guess which lobe got wiped out. This bad advice might be out there causing harm.
    I still liked the guy. After replacing the cam, and then spinning a rod bearing, ( at 95 MPH ) we came up with a rebuilt 283. YAY.
     
  16. Pete Eastwood
    Joined: Jul 27, 2011
    Posts: 1,019

    Pete Eastwood
    Member
    from california

    condensor
     
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  17. Squablow
    Joined: Apr 26, 2005
    Posts: 15,124

    Squablow
    Member

    Kinda unrelated, but my dad's 56 had a Pertronix installed into the stock distributor and it gave the exact same issues. After trying everything and pulling our hair out we found out that the Pertronix unit does not clock in the same position as the factory points, so if you put the unit in with the distributor in the same position it was in with points it ends up being like 15 degrees off. And those 235's only have a small bit of adjustment in them so you actually have to loosen up a collar on the distributor and turn it to get it within the adjustment range, then tighten it back down and dial it in at the adjustment.

    Once we had that figured out, the car ran beautifully.

    After having issues with that and one of my other cars with an aftermarket electronic ignition, I feel like they sometimes cause more problems than they solve. But the issue of good quality ignition points and condensers being so hard to find makes them tempting to use.
     
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  18. 6sally6
    Joined: Feb 16, 2014
    Posts: 1,578

    6sally6
    Member

    Usually..most carb issues are "ignition issues"!;)
    Put some more advance in the timing.
    A lot of times....when the timing is sorta retarded (like a lot of us!:eek::eek:) it will let unburnt fuel mixture go into the exhaust system. And then it backfires!
    I used to do it on purpose because it sounded like a gun going off! (stupid teenager...I'm sure no one else ever did that!!)
    Anywho give the distributor a little twist (advanced) re set idle and see what happens.
    6sally6
     
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  19. MAD MIKE
    Joined: Aug 1, 2009
    Posts: 626

    MAD MIKE
    Member
    from 94577

    Do you recall which Pertronix you used?
    IIRC the units for the Stovebolt will only work on 12V, if you are still running 6V it won't work/work properly.
    Black is regular Pertronix and does not take well to being left powered on with the engine off. They tend to burn up.
    Red is Pertronix II and the ignition can be left on with the engine off and it will not burn up.
    If the ground system is weak it doesn't work too well.
    Was it sputtering or was it just lazy?
    I would recheck anything that you may have touched during that change over and re-verify that something was not knocked loose, installed backwards/upside down/etc. Eyeball the coil and it's connections are good and tight.
    How were the old points looking before you removed them?
    Do you still have the old set of points/condenser?
    If you do, put those back on and note if there is any change in running condition.
    Don't recall an actual dwell degree, just gap setting with feeler gauges. But IIRC the dwell was smaller/longer on the 53/54 than the earlier or later Blue Flames.
    If the spark is weak the plugs will foul and load up.
    A quick check for spark quality is to crank the engine while grounding a plug wire to the block.
    You should have a nice white-blue spark from the wire to ground. If it is orange then the spark is weak.
    What else did you change when you went to the Pertronix conversion?
    Pertronix will need 12V negative ground to work properly.
    Usually bypassing the resistor for the coil as well.
    And the plugs/wires need to be changed to resistor type.
    If none of the above was done when you changed to Pertronix it would never have worked correctly.

    When you switched back did you put everything back the way it was supposed to be?

    Going back to the plug boots popping off, if that has happened enough times, plus a pertronix or 12V conversion with the 6V coil and/or no resistor, this will stress the coil. Having a very high resistance or even ∞ resistance will damage the coil.

    I'd pull a plug/plug wire, ground it against the block and take note of the spark plug color when cranking.

    If that looks good, get back to basics.
    Verify valve lash is not tight, timing is spot on(put it back to factory spec) and readjust carb/idle. If there is anything that is not factory, list it. Something that may seem mundane may require a different tune/setting.
    Currently I'm assuming your engine is a stock rebuilt unit.
     
  20. anthony myrick
    Joined: Sep 4, 2009
    Posts: 8,107

    anthony myrick
    Member

    Mine did similar
    Ballast resistor was messing up, killing the points.
     
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  21. MAD MIKE
    Joined: Aug 1, 2009
    Posts: 626

    MAD MIKE
    Member
    from 94577

    Don't forget, someone besides the factory has had your engine apart.
    Pull the distributor cap off and see if your mechanical advance still works.
    You will be able to slightly rotate the rotor in one direction, it should snap back when you release it.
    If it does neither, your timing plate could be goofed up as well.

    As Jim and Anthony have said, a bad condenser will cook the points.
     
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  22. garyf
    Joined: Aug 11, 2006
    Posts: 241

    garyf
    Member

    I agree with jaracer sounds like electrical issue . I would also check the distributor shaft for wobble. It was common on inline G.M. ,this would change your dwell under load. Also at idle grab your engine wiring harness a give it a tug, see if the engine stumbles indicating a electrical wire poorly connected or shorting or on exhaust system.
     
    Last edited: Jul 19, 2021
  23. 4doorsformorewhores
    Joined: Jul 7, 2021
    Posts: 61

    4doorsformorewhores
    Member

    So let’s start by saying big thanks to everyone of you, because all the feed back and helping me compile a checklist (that’s within my very small wheelhouse) has been awesome. I spoke to a friend today who said condenser as well, and it dawned on me that my attention should probably be turned towards electrical/ignition. Thinking back, when the issue first started rearing it’s ugly head the car would “lunge” or momentarily lose power on the freeway. One of these incidents I happened to have had my eye on an aftermarket tach I have in the car and it dropped rpms almost completely, and then caught them again like it never happened. Also it has been quite the struggle to achieve anything over 2500rpms in 3rd. So condenser is starting to make more sense, or perhaps a weak spark in general. Plugs were a bit dry and fouled too, so I know mike here said a weak spark could cause some build up. I think my first items on my list will be swapping the condensor, as I have a new one in the glovebox, and then if that doesn’t do it, maybe test them coil and see it’s condition. More history the car has been converted to 12v. No ballast resistor present, but there could be a resistor wire for all I know, that I’m not sure of. I did a few months back but a flamethrower coil with 3ohms of internal resistance, not sure if that’s could for old points
     
  24. anthony myrick
    Joined: Sep 4, 2009
    Posts: 8,107

    anthony myrick
    Member

    On a side note.
    The overseas condensers are a crap shoot.
    Keep an extra one
    Buy NOS if possible.
     
  25. anthony myrick
    Joined: Sep 4, 2009
    Posts: 8,107

    anthony myrick
    Member

    my 12v GMs with points has an external resistor.
    My 12v Ford with points has a resistor wire.
    the electrical gurus can chime in on the coil you are running.
    My coil says “must use external resistor”
     
  26. Truck64
    Joined: Oct 18, 2015
    Posts: 4,743

    Truck64
    Member
    from Ioway

    Condenser is a critical ignition part, I'd say the el-cheapo no name junk are worse than a crap shoot. At least in craps, ya have a chance to win!

    NOS or a quality unit is the way to go. If you're gonna run points, you have to have a good condenser. Buy a few of them, and have them tested by somebody who has the right equipment. If your ohmeter or digital "cap checker" can apply 500 volts DC , that is the right equipment. Hint: It can't.
     
  27. 4doorsformorewhores
    Joined: Jul 7, 2021
    Posts: 61

    4doorsformorewhores
    Member

    Electrical gurus feel free to chime in! Electrical and me do not get along. I’m a plumber by trade, and even wiring up a sewage ejection pump might as well be heart surgery to me :(
     
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  28. 4doorsformorewhores
    Joined: Jul 7, 2021
    Posts: 61

    4doorsformorewhores
    Member

    I really had no idea a condenser would cause this much issues, but again, electrical is foreign as hell to me, so this 54’ is teaching me a lot! I’m hoping tossing in a new helps the sitch, or at least allows me to cross one thing off my list
     
  29. anthony myrick
    Joined: Sep 4, 2009
    Posts: 8,107

    anthony myrick
    Member

    A ballast resistor knocks the juice down after ya start it up.
    When it goes bad, the distributor get the full 12 causing points to stick and act goofy.
    Pops, misses, backfires, stalls.......
    In my experience, most of the time, condensers just die. But I had one sputter, spit and act like it’s was out of gas once.
     
  30. greybeard360
    Joined: Feb 28, 2008
    Posts: 1,743

    greybeard360
    Member

    I have never seen a ballast "go bad" and output 12V..... If a ballast goes bad it creates an open so you lose voltage.
     
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