Chasing advanced timing

Discussion in 'General IH Tech' started by binderplanet-ron, Jan 13, 2015.


  1. binderplanet-ron

    binderplanet-ron Farmall Cub

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    Hi all. I've got a '72 345, 2bbl., in a Kurbmaster, bolted to a manual.
    Newly rebuilt original carb, new plugs, Pertronix ign. and coil, wants 20 + degrees of advance to start up, kicks back at the starter a little but runs well. Also, it stated up with 15 degrees the other day, but was hesitant when the throttle was bumped, but now it won't start with anything less than 20+ degrees. I'm scratching my head. Thoughts?

    FYI:
    My timing light is hooked up to #8
    The coil has battery voltage when the key is on and drops 2 volts while cranking
    The distributor shaft doesn't wiggle
    Two new fuel filters, before and after the pump, and new pump to carb lines
    New valve cover gaskets, while off checked to see all valves were moving
    Plug gap is correct
    Sprayed carb cleaner all over the intake and carb with no idle increase
    Rotor and cap are new
    Float is adjusted to a trickle after a jostle
     
  2. walkersscout

    walkersscout High Wheeler

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    Bad balancer?, timng off wrong cylinder?

    Looks like your coil wiring is bad. You should have a full 12 volts when cranking. Check the wire from the starter solenoid to the coil, as that is where it gets it from.
    Pull a plug and leaveit connected and ground it have someone crank to see if you have a good strong spark
    Also, make sure you know which cylinder is #8, would cause a problem if you were on the wrong bank.
     
  3. binderplanet-ron

    binderplanet-ron Farmall Cub

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    I'd expect a voltage drop durig cranking, but I don't know what the stock number is. Also, I'm running a high torque starter and an after market ignition switch so power to the coil is always from the ignition switch on this truck, as the High torque starter requires a diode if you want to run power from it.

    I'm also timing from number 8. Set the timing to 8 degrees or so BTDC and it will not start. Advance it to 20 + degrees and it starts with starter kick back.

    Are there areas where the manifold is prone to leak? I cannot find a photo of the underside of one, as a vacuum leak is my only thought.
     
  4. TheScoutMaster

    TheScoutMaster High Wheeler

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    Are you absolutely sure that TDC on the crank/harmonic balancer is where #8 is on the dizzy? Your harmonic balancer may have slipped. Get your balancer/crank timing mark to TDC and check the stroke on #8 with a dowel rod, etc. while someone manually turns the crank... or your 180 degrees out of phase, not timing on compression but exhaust?
     
  5. Paul "Misterfixit" Schulz

    Paul "Misterfixit" Schulz Super Mod from Downunder Staff Member Administrator Moderator

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    Hook a vacuum gauge to the inlet manifold and start the engine, then with it warm adjust the timing until you get maximum vacuum at idle, that is the theoretical best spot for timing, then recheck the balancer to see where it reads, if the reading doesn't look right recheck the top dead center mark on the balancer in relation to piston position.
     
  6. binderplanet-ron

    binderplanet-ron Farmall Cub

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    I pulled my distributor and cleaned it, tested the grounds and installed it. I'm getting better spark now, but it isn't starting. I used my compression tester to find #8 compression and set the harmonic balancer mark a about 6 degrees BTDC. I installed new spark plug wires and tested the spark, its much brighter now. It sounds a lot like my old 392 when the battery was dying, so I popped it on the charger, but I had spark and it was brighter after I cleaned the distributor ground, so perhaps it's the mixture now.

    Does anyone know how many turns the idle screws should be from bottomed out? (stock '72 2-bbl holley)

    Is there any chance that the 6 degrees were too much?
     
  7. TheScoutMaster

    TheScoutMaster High Wheeler

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    6 degrees on timing (dizzy advance) or 6 degrees set on the balancer itself? You should be at TDC on the balancer, and then once it starts and gets to running temp the advance on the dizzy is adjusted to whatever specs are. The advance vac port should be plugged while doing the initial timing.
     
  8. binderplanet-ron

    binderplanet-ron Farmall Cub

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    Hey Paul "Misterfixit" Schulz, I didn't get back to your post, the problem is that I cannot get it to start, but once I do I'll definitely break out my vacuum gauge to tune it. Thx.
     
  9. binderplanet-ron

    binderplanet-ron Farmall Cub

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    Hey TheScoutMaster, I took your advice and retimed it to #8 TDC on compression at Zero on the timing mark. Thanks.
     
  10. TheScoutMaster

    TheScoutMaster High Wheeler

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    Were you able to get it started?
     
  11. binderplanet-ron

    binderplanet-ron Farmall Cub

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    No stating yet.
     
  12. binderplanet-ron

    binderplanet-ron Farmall Cub

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    It's running now 30 degrees advance, reading about 20 on the vac gauge. If I try to retard down from 30 it stalls and will not start.
     
  13. Albuq. Henry

    Albuq. Henry Binder Driver

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    I have an advance timing light, one time while using it I could not get a reading that made sense. I ended up getting another one, el cheepo from autozone, that was fixed. turns out My light was off and not showing correct setting.... another time while starting a truck that had been sitting, all of a sudden timing was off... turned out the mechanical advance was way dirty and sticky with old grease, at high RPMs the weights moved and the old grease kept them in that position even while at idle....
     
  14. binderplanet-ron

    binderplanet-ron Farmall Cub

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    So, I've scratched my head a bit and done some due diligence. My buddy pointed out that the vacuum gauge during cranking was barely 5 ft. lbs., and if you cover the carb inlet while cranking you could barely feel the air being pulled it, much less than a breath through the fingers. I pulled the carb, removed the fiber composite spacer and covered the holes in the intake while cranking, with all the gasoline pooled up in the intake it almost started with my hand for a carb! Though it wouldn't have felt very good to have my hand sucked to the intake for very long. But the point is there is a tremendous amount of vacuum pulling in through the intake compared to the when the carb is installed. So, a couple questions...

    On my 2 bbl. intake there is a third smaller hole between the two inlets and towards the rear of the engine. What is that and what does it do, could it lead to a potential vacuum leak?

    Looking over the numerous 2 bbl. Holley threads, specifically around my "454578-C91 List-6391-2" (a.k.a. the 2300?). Is the internal gasket voodoo enough to cause a 345 with 130 ft. lbs. of compression to not start?

    I ordered the Fel-Pro 66-607 base plate gasket, shorter carb studs, and some bulk rubber-fiber paper to cut my own base gaskets, and with them in place it started, though it only runs with 30 degrees advance, any less and it stalls and will not start again....

    thoughts?

    Oh, and it's the original carb, rebuilt my The Carb Refactory in Richmond, CA.
     
  15. binderplanet-ron

    binderplanet-ron Farmall Cub

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    Hey Albuq. Henry, I pulled and cleaned the distributor, the weights are able to move and rest in their proper position, though the small spacers are missing the weights require a lot of work to move apart. What is the total advance that mechanical weights provide?
     
  16. Smog_guy

    Smog_guy Binder Driver

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    I'm an old mechanic, I've seen lots of things...
    One thing you haven't talked about is a distributor out of phase.... kinda rare but happens. I've seen it about three times in forty years.
    What could be going on then is that the coil is getting the "let go of the spark" signal while the rotor is midway between two distributor cap terminals. It will flat drive you crazy.
    So, when there is no load on the engine the spark (from rotor to cap) wants to jump to the correct cylinder. Under load the spark would rather jump to an easier cylinder to fire.
    Yes, the distributor rotor seldom points right where it should, anyway. In the "out of phase" scenario it's WAAY off.
    If you haven't already, and you know how to stab a dustributor, try another distributor.

    And yes, this scenario will cause a no-start!
     
  17. binderplanet-ron

    binderplanet-ron Farmall Cub

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    Hey Smog Guy, that's a great idea. I've got a 73' 392 points set up to try. The '72 345 has a Pertronix set-up. Does anyone know if my 392 set up will plug and play?
     
  18. Albuq. Henry

    Albuq. Henry Binder Driver

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    I dont know the exact amount of total advance but wanna say 20-25*
     
  19. binderplanet-ron

    binderplanet-ron Farmall Cub

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    I'm at my wits end over this, but determined to crack it.

    Reasons for an engine running only with 30 degrees or more advance....

    Lean mixture
    Cam timing
    Vacuum leaks

    Are there any other reasons?
     
  20. kevingweq

    kevingweq Y-Block King

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    The 2 most logical explanations so far are , 1 malfunctioning timing light, 2 distributor out of phase

    I noticed you have said you have been timing on number 8 compression ,But have you verified the piston is in fact at top dead center ,??
     

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