Timing and idle question

Electrical & Ignition

  1. Castle

    Castle Member

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    hi everyone, I have been working on a 1968 Newport....bought it last July. In adjusting timing and idol, I can’t seem to get the curb idle at the spec from my FSM. It calls for it to be set at 600- 650rpm.... but as soon as I get it below 725, the carb starts to have a high whistle sound. Any ideas as to what causes it to do so?
    Next question..... I upgraded to a Pertronix mechanical distributor, it seems as though the base timing is way advanced from the FSM spec, is this normal.... the manual spec says base is At 7.5 and it seems to run pretty well between 24 and 28.
    Thanks for your input!
    ps.... I have a new timing light, digital, with advance and rpm.... among a coiuple of its options.
     
  2. 67Monaco

    67Monaco Old Man with a Hat

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    what does the vacuum gauge read?
     
  3. Castle

    Castle Member

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    Ok, I’m going to expose my inexperience, vacuum of what part?
     
  4. 67Monaco

    67Monaco Old Man with a Hat

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  5. Castle

    Castle Member

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    Thanks, I will check them out, right now.
     
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  6. 67Monaco

    67Monaco Old Man with a Hat

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    teach a man to fish and all that...
     
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  7. CBODY67

    CBODY67 Senior Member

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    You said "mechanical" distributor? Does that mean there are no advance weights in it and there is no vacuum advance on it, either?

    Set the base timing to spec, as stated in the FSM. Do this first.

    Then, with the engine stopped, gently turn the idle mixture screws clockwise until they "seat" in their holes. Then turn them 1.5 turns counter-clockwise. That is usually the base adjustment for the idle mixture. Then, start the motor and try to set the HOT base idle speed to about 625rpm in "P".

    IF you can get there, then individually turn each mixture screw out about 1/8th turn to see if the idle speed changes. Then back to the original setting and 1/8th turn in. What you want to do is aim for the highest rpm with that original speed setting. Then from the higher speed from the mixture screw tweaking, put the rpm back down to 625 in "P". Then repeat until you have the "lean best idle" at the noted idle speed in "P".

    Once you have all of that done, the final adjustment is to turn each mixture screw in to achieve a 20rpm drop in idle rpm with EACH screw, then the adjustment back to where the last setting was. "Lean Best Idle". Not too rich, not too lean.

    In the distributor, there should be a pair of "fly weights" which will advance the timing as engine rpm increases, to a point. Just as the orig distributor did.

    Please advise of your progress.

    CBODY67
     
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  8. Castle

    Castle Member

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    The new distributor is of the mechanical type, no vacuum advance, only done with rpm and the weights, as you state... the carb is a new/reman, from Autolite. New plugs (E3’s), new wires, new coil (matched from the distributor manufacturer), new gas tank, sending unit, fuel lines from the tank to the carb, and new fuel filter.every hose, valve, fitting on the engine is new, as well....
     
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  9. Dobalovr

    Dobalovr Being on the Cbody diet SUCKS! FCBO Gold Member

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    Non vacuum advance dizzy in a 68 Newport? More info on this setup please or maybe a picture or two.
     
  10. CBODY67

    CBODY67 Senior Member

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    Similarly curious as to the desire for a non-vac advance distributor?
     
  11. Castle

    Castle Member

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    Vac advance on a distributor just seemed like one more place for a leak/ issue. The original distributor vac diaphragm was shot, otherwise I would have just put a points eliminating plate in the original distributor.... I just felt it was easier to replace the entire distributor.... I’m not restoring the car, just giving keeping it from going to a crusher. OE does not matter to me, just safe and running.... a mechanical without vacuum diaphragm should work just fine.
     
  12. Castle

    Castle Member

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    The car runs pretty good, I’m just trying to understand the timing..... because where I have it set, versus what my factory service manual spec says it should be set at.... trying to fine tune it, and understand it. I can’t possibly be the first guy to eliminate the vac adv on a 383distributor?
     
  13. CBODY67

    CBODY67 Senior Member

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    It will work just fine . . . except . . . the vac advance is there to increase part-throttle fuel economy and throttle response. At cruise, the initial base timing + mechanical advance + vacuum advance can be about 55 degrees BTDC timing advance. Which is fine for cruising on the highway. Of course, when throttling into the engine, the vac advance will decrease down to "zero" near WOT, so then you've only got the base + mechanical at work.

    Many of the "racers" in the later '60s would limit the vac advance and rely mostly on the centrifugal advance when they'd "re-curve" a distributor. Claiming it was "more consistent" in operation. Usually, with increased base timing, too.

    When I was driving the '66 Newport 383 2bbl all of he time, I noticed that the mpg went down a bit. I checked everything and it was all good. Except the vac advance. I didn't have time to chase one, so I just capped the vac line and drove it a few days like that. Lost about 4mpg on the average (from 16 down to 12), ouch. Got a new one and installed it. Mpg came back and it ran better.

    Back in the '70s, on the medium-duty trucks Chev sold, those particular application distributors did not have vac advance on them, from the factory. I thought that curious, so I asked the service manager about that. His reply was that those trucks were generally under enough load that the manifold vacuum was low enough that the vac advance added little if anything to the mix. So they just deleted it. Which explained why those engines always sounded "laboring" even when they were cruising around empty. Compared to the similar car engines that had vac advance units on them.

    Thanks for the information,
    CBODY67
     
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  14. Castle

    Castle Member

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    You called it, with just one word.... everyone I deal with, are from the racing world.... but almost none of them are Mopar guys.... only one guy is an old Mopar tech.... so when I have questions as to why my timing might be so high, its just because this kind of modification is kind of foreign to me, not stock.... as I said, it runs and drives pretty good, but I get weird feelings when I have to advance so much higher than OE spec.... going from 7.5, to 24, is a little scary.... and I feel like it even needs to go a bit mor to be more on point.... I had it up to 29, but on hard acceleration I could hear the valves yelling at me.

    I am curious to put a vacuum gauge on it and see how it reacts.... I’ve only been using a light and test driving it.

    Thank you for your input... I really appreciate you taking the time... I am trying to learn and this forum can, and has been,be a great resource.
     
  15. CBODY67

    CBODY67 Senior Member

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    What you probably need to do is to get a "dial-back" timing light so you can monitor just how much or little mechanical advance is in the distributor, as it sits. Plus when the advance starts.

    On the '66 383 2bbls, the base timing was 12.5 BTDC and everything worked fine. I even put it up to 15 degrees with no problems starting or such. BUT, at that 12.5 base timing, the total advance at 4500rpm was right at 38 degrees BTDC, which is optimum for a Chrysler B/RB motor . . . just as it is for a small block Chevy.

    In the earlier Chrysler Direct Connection Race Manual, they advocated aiming for 38 degrees total BTDC, "all in" at about 2000rpm . . . for racing purposes. On a street car, it probably needs to come in a bit slower. Seems like the old Direct Connection electronic ignition kit distributors had a faster curve, all in by 3000rpm?

    It seems to me that if you need to put that much base timing into the motor, then there is probably little mechanical advance in the new distributor. Hence getting the dwell tach and dial-back timing light to see just what is in there at what rpm.

    ALSO, don't forget that the outer ring of the damper might have moved, which will give you incorrect timing settings. When those outer rings usually move, they can rotate some, but will almost usually also move backward. Which should be obvious. Seems like they are the same as on the small block Chevy motors. When #1 cylinder is at TDC, the crank keyway is parallel to the #1 connecting rod at that time. I'm thinking that's the way it is, but it's been a while.

    Enjoy!
    CBODY67
     
  16. BLUPORT

    BLUPORT Carpe Diem Cras FCBO Gold Member

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  17. Castle

    Castle Member

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    Just looking for as much input as I can get.
     
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  18. Castle

    Castle Member

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    Ok, here is the current situation.... today, I opened up the distributor cap.... a pertronix unit, and switched out the springs inside the rotor.... the unit came from the manufacturer with their middle of the road tension springs installed.... I swapped out those ones for the softer springs.... two minute job.... started her up and started to roll out of my parking spot... before I made it 10 feet, I could already see a ton of improvement.... when I turned onto the highway, instantly pleased with a very smooth and non hesitating slow acceleration.... once up to 55 mph, cruised without any loping.

    So, I just needed the distributor to be able to advance easier, basically...

    Thank you for all the assistance, gentleman!