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  • 1 Post By jerry clayton
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Thread: Setting Timing on 383
          
   
   

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  1. #1
    rdobbs is offline CHR Member Visit my Photo Gallery
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    Setting Timing on 383

     



    Helping my son (same name) on his 383 build, and have question
    on all in timing. Cam lift is 645 and using MSD everything. We were
    shooting for 36 deg all in timing at 3000 rpms. Here is what we got.

    Car wants to idle best at about 1800 rpm and we get 12 deg.
    At 3000 RPM it goes to 22 deg
    At 3500 RPM goes to 25 deg
    At 4000 RPM goes to 30 deg
    at 4500 RPM goes to 32 deg

    Car starts good, revs good & cools good. We changed bushing
    in dist with no change. We are currently running a silver and
    blue spring in dizzy as well as the blue bushing.

    What are your recommendations on getting 36 deg all in timing, or
    are we ok where we sit. Thanks

  2. #2
    jerry clayton's Avatar
    jerry clayton is offline CHR Member Visit my Photo Gallery
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    needs to advance much sooner-should be to where you wantit at cruise speeds--------

    why is it idling at 1800???

  3. #3
    rdobbs is offline CHR Member Visit my Photo Gallery
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    Jerry, it was idling pretty good at 1000 before we took dizzy out
    and replaced bushing. Is it possible we could be off one tooth on
    distributor? I would think if so, it would mis fire some. One other
    strange thing is when we kill engine the tach wants to remain at
    around 1000 on gauge.
    Right now if you try retarding timing to get to 1000 rpm idling
    it wants to die. If you leave timing as is and adjust idle screws on
    carb same thing.

  4. #4
    jerry clayton's Avatar
    jerry clayton is offline CHR Member Visit my Photo Gallery
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    Maybe tack is wrong???????

    I would get a back up tach to verify rpm

    I would take a piece of wire and tie dist advance solid to remove any advance, and then start car , see what it likes at idle, then see what it likes to rev up with, fix dist weights/springs so as to accomplish that advance ment as rapidly as possible and then put in the bushing that would give me that amount of degrees with the lightest springs possible that will pull the weights back to idle for shut down without dieseling
    Last edited by jerry clayton; 03-13-2017 at 11:49 AM.

  5. #5
    Rdobbs1977's Avatar
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    Car Year, Make, Model: 1972 Z28 Camaro Drag Car,2500lbs w/motor
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    we've got a tach on another car that works with msd 6al and can pull it to use. perhaps we've got faulty timing numbers and a 'faulty rpm idle' due to a bad tach or something going on with it. we'd thought maybe there was something going on with the tach yesterday because after pulling the distr and putting in a different bushing, the timing numbers made no sense with the timing light vs what we should have had on paper using what we used. its very strange that on our previous setup with distr., the car 'idled' at 1000 rpm. we take distr., out put a different bushing in, and right off the bat the idle was way off, despite us using the same base time. so we put the old set up back in and same thing.

    Jerry, these may be some rookie questions but here goes just to confirm:
    1. are you saying we just tie the two dog ears shut (or remove) so as to eliminate any mechanical getting mixed in with initial in order to set base?

    2. if so, are you saying with the ears still tied shut, we bring it up to the desired rpm curve (2700?) and measure what those degrees were from base to get us there? Then with that info we choose what springs and bushing on paper that will get us close to that?

    3. when we do yank the distr like before, we yanked it at about 5-8 degrees BTDC. is that ok or should it be on TDC exact when we remove?

    Thank you Jerry,
    2.
    1972 Z28 Camaro, Full Drag Car, 383 CID
    1976 Camaro
    Currently building a 1.21 Gigawatt Flux Capacitor

  6. #6
    Rdobbs1977's Avatar
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    i think we may have figured out our problem or at least 90% sure we have. Today we put motor on True TDC. Rotor was where it needed to be. Took distributor out. Found that one of my springs when i took it off had a small gap in its coils. That’s probably because one of us man handled the spring last weekend and was prob too aggressive with screwdriver. This time i used my hands and replaced the bad spring. So i knew then that spring had something to do with my bad timing numbers. Drop distributor in and like before the motor sounded good but the RPMs i was showing on my tach did not feel right as my ears were doing a better job. Tach was showing 3000 RPM with my foot on pedal but i knew it was not that high. About the time thermostat opened, my foot still on pedal in same spot, the tach then just goes down to 1500 with to much play too in the needle for me.. Put timing light on there and it all jacked up. So disabled the tach, put a different tach on there, and that tach was spot on. First numbers we got were: Base-12, 3000-25, 4000-25. So i knew it was not advancing. Did not want to take it up to 5000RPM cuz i figured if it did not change from 3000-4000 then it was not going to change anymore. So we up my base time and advance it 10 degrees. At 3000 RPM I now have 35 degrees. Sooooo, i hope we've fixed our problem. On saturday we going to take the tach off car and rig it up on our test motor. I’d assume its not going to work or do its job but want to see. That tach is an Autometer Sport Comp Monster w/push button display and shift setting for shift light on it. The spare tach i used today was just a cheapo so i may be in for having to buy a new tach. So now i have more questions:

    1. Other than what i did today with changing out the tach and in a few days taking that ‘bad’ tach and putting on my test motor to test, i reckon that’s the only way to test if tach is bad that i know of. I don’t think there is anything on the car that could have been bad to make the autometer give false readings, right? that cheapo tach i put on there for testing, worked like it was supposed to.

    2. Getting back to timing, i’m going to put timing light on there again on Saturday and make sure car starts up on cold, hot, etc. The last time we adjusted it to advance it and give me 35 at 3000, i forgot to shine light on there for base time. On paper though, i’d think i’d be running about 20 degrees. I assume that’s ok with a high performance motor right?
    1972 Z28 Camaro, Full Drag Car, 383 CID
    1976 Camaro
    Currently building a 1.21 Gigawatt Flux Capacitor

  7. #7
    jerry clayton's Avatar
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    Your talking about 100% MSD and in there directions are specs for the advance with different springs/bushings-read the directions----

    for a competition deal you can just lock the advance solid and use a retard system for starting-------

  8. #8
    Rdobbs1977's Avatar
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    Jerry, i read the curve charts. Read them over and over and over so perhaps its more of an understanding issue for me at this point. So for understanding let me ask this. Say the car comes it at 35 degrees all in at 3000 rpm. This car is going to launch at prob 4300 RPM. So at 4300 its still going to be all in at 35 at that RPM. So the cylinders are getting optimum combustion i would think. The timing curves show 'guys uses this bushing and springs, guy gets 'x' degrees in' at 2700 rpm, 3000, what have you depending on combo used. So that's where i get confused maybe....if i'm launching at 4300 RPM at 35 all in, are you saying this is wrong? Or put another way, what would be the big difference being all in at 2700 vs 3000 on my set up? Car's never going to see those RPMS anyhow..? Thanks,
    1972 Z28 Camaro, Full Drag Car, 383 CID
    1976 Camaro
    Currently building a 1.21 Gigawatt Flux Capacitor

  9. #9
    jerry clayton's Avatar
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    Put a crank trigger on it and a retard relay for starting--------lock the advance ---this is a track car right?????

  10. #10
    Rdobbs1977's Avatar
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    Jerry, I've heard of guys running zero mechanical and putting it all at the crank or at least trying to put as much as they can at the crank with little coming from mechanical. What are the advantages if a guy locks out mechanical advance? Just looking to improve my knowledge, thanks. (yes its a track car)
    1972 Z28 Camaro, Full Drag Car, 383 CID
    1976 Camaro
    Currently building a 1.21 Gigawatt Flux Capacitor

  11. #11
    jerry clayton's Avatar
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    Advantage is better performance but maybe difficulty starting so you use a retard device for starting and you can actually run more timing intermediate range if you knock off a few degrees in high gear
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  12. #12
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    Since you're just starting out at this point. Don't get all hung up on this topic. Get a setup going that lets the car start and at least "feels" powerful.
    Then make some passes with that setup. Record the results with that tune. Then you can start making changes and see what works and what doesn't. Let's say you do launch the car at 4 to 4300 rpm, depending on how "sticky" the track is, you could pull rpm's down to say 28 or 2700, then you'd be losing advance if it needs to get to 3 grand.....

    But right now, that may not be an issue.... you just won't know 'til you start making passes. HTH.., my point oh 2, fwiw, yada yada yada...
    Rdobbs1977 likes this.

  13. #13
    jerry clayton's Avatar
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    well actually you can easily start it with the timing advanced-you just need a start button that you can turn the engine with and after a few turns hit the ON switch and it'll start---however the retard deal will allow you to use chips for the amount you want to retard in high gear-----

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