Question on optimizing base timing

Discussion in 'Engine Topic' started by mrluckies, Sep 21, 2019.

  1. mrluckies

    mrluckies Veteran Member Lifetime Gold Member

    Messages:
    459
    Likes Received:
    47
    Joined:
    Dec 31, 2001
    Location:
    temporarily Germany, normally NJ
    are there any good indications of how to find optimum base (initial timing)?

    Most people say set it at 10-14 deg and forget it.

    Others say, set the max total advance you want and don’t worry about the base timing. I plan to recurve my distributor so this isn’t an issue (I.e. limit my mech adv once I know what base and max timing it wants).

    I’ve seen the articles showing to set base timing with a vacuum gauge, but when I do that, my base timing is over 30 deg! I guess I could set base lower and then add vac adv to get to that point? But base timing itself, that seems too high.

    I’ve also heard people (including msd) say keep adding base timing until the starter has a hard time with a hot engine and then back off a deg or two.

    I know I want as much base timing as the engine will tolerate. Just by going from 10 deg to 16 deg it runs cooler and is more responsive and doesn’t smell out the exhaust as much. Since the car is primarily a cruiser, base timing is more important to me than total timing.

    I’ve tried driving the car up a hill in 4th gear to listen for pinging, but my headers are loud and I hear the ticking from them. I’m still checking to see if I have an exhaust leak causing the ticking.

    I’m looking for methods on how to determine timing requirements, so the engine specs shouldnt matter. I’m not looking for a timing number to shoot for (if I was, I’d probably set it around 16 base and 36 total on a mild bbc) but rather a systematic method to determine I have the timing my particular engine wants with the gas I use at the altitude I live, etc, etc....

    Appreciate any advice, thx!
     
  2. CorkyE

    CorkyE Veteran Member Lifetime Gold Member

    Messages:
    10,213
    Likes Received:
    415
    Joined:
    Nov 4, 2004
    Location:
    Ringgold, GA
    FWIW - I have the Eddy ProFlo 4 setup, technician had me set 20* at idle, I've since pulled it back to 18*. That's probably a bit much with a mechanical distributor. I agree with MSD and you can always install a start retard box. Most CDI boxes have that feature.
     
  3. jeff swisher

    jeff swisher Veteran Member

    Messages:
    1,253
    Likes Received:
    373
    Joined:
    Apr 26, 2018
    Location:
    Yukon Oklahoma
    Usually 18-24 on all the engines I have had or built for friends.
    You are correct in the exhaust smell will be less with more timing and lean mixtures really want a bit more timing.
    Quiet exhaust really helps for nailing down the tune.
    If it likes 16 best then go with that.

    The starter struggling from too much timing is not a good idicator vacuum gauge is not either.
    The best is driving it and giving it what it wants to perform best.

    My total is usually all in by 2400 rpm or sooner.
    I want all the total timing in by cruise rpm..If you cruise at 2000 rpm you may be best served having all timing in by 1900 rpm.
    I do give my engines as much base as they like and as much total as they like.
    Sometimes it gets a bit tricky to get there but I do tricky quite well.
    I had 2.29 rear gears and 31x10.5x15's with a TH350 I had that combo running all in before 1600rpm to get my MPG up.
    All in by 2400 and MPG was 8. and that did not work well at all.
    Fun gear for running 145 in second gear though.
     
  4. biker

    biker Veteran Member

    Messages:
    767
    Likes Received:
    55
    Joined:
    Dec 7, 2014
    Location:
    New Liskeard Ontario Canada
    I look forward to Jeff's opinion on this, but I think weaker springs on the mechanical advance would get total timing in quicker, but also increase your initial timing a little bit without having to move the distributor to make a gain in initial timing. This might allow you to get a bit more initial timing (say, in the 18 degree range) without bumping up the total timing which would cause you to get into pinging.

    I'm going to experiment with my HEI since my all-in mechanical advance doesn't get there til 3000 rpm. I'd like to quicken that curve to be all-in by 2500. I will share what I learn about spring tensions and their effect on curve.

    I should be able to get a ballpark idea fo spring weights with a fish scale.
     
    jeff swisher likes this.
  5. jeff swisher

    jeff swisher Veteran Member

    Messages:
    1,253
    Likes Received:
    373
    Joined:
    Apr 26, 2018
    Location:
    Yukon Oklahoma
    I am 51 years old sometimes do not explain everything you may need to get to where you need to go.
    I sometimes assume we have all been there.
    I was 17 when I began playing with weights and springs.
    I had a friend that worked on copy machines and cash registers.
    He pulled one register apart and it had a bunch of small light springs in it with loop ends..SCORE!

    I have even ground the tips of the weights into a slight curve shape a bit to get more mechanical advance.
    I have taken my AC225 welder and 6011 welding rod and laid a bead onto the top of the weights to make them heavier so they could overcome the stiff spring.

    All kinds of things you can do to get there.. but I did not check weight with a scale.
    I just did it and installed it and read what I got with a timing light and went from there.

    I got really good at pulling distributors and taking them apart and sticking them back in quick like.
    Ford, GM, Mopar, Datsun it did not matter I was tweaking on them if I felt I could gain power or MPG.
     
  6. mrluckies

    mrluckies Veteran Member Lifetime Gold Member

    Messages:
    459
    Likes Received:
    47
    Joined:
    Dec 31, 2001
    Location:
    temporarily Germany, normally NJ
    Thx for the replies!

    Is there an easy way to figure out what the engine wants? What are you looking for? What symptoms/noises etc. What type of driving do you do to find out if it’s right? Flat road or hill? What gear (1:1 gear is what I’ve heard most say)?

    I never got the car to surge while driving down a flat road at constant speed.

    I know with my current combo, I have 16 deg initial (I have to re-check the timing tab accuracy, I did when I assembled the engine, but forgot that I can’t look straight down with the water pump and accessories installed, so from the current view I might be off a deg or two). I also have manifold vacuum for the vac adv adding 10-12 extra degs (idles about 18 in hg). With vac adv disconnected, it idles hot and the floor of the car gets hot (long tube plain steel headers). It also seems a bit sluggish. Adding the vacuum adv, the temp never climbs and the floor feels cooler. Car is more responsive and doesn’t stink up the garage when parked. So it definitely wants the added advance.

    I thought I heard “pinging” when driving with the adv, so I disconnected and still heard “ticking”. I then backed it down to 10 initial and no vac adv and you could really see the temp gauge difference (no fan shroud and mechanical fan and clutch). Car was even more sluggish too. I still heard the ticking noise, now I’m pretty sure it’s actually from the headers and not actually the engine pinging. It’s not a high compression engine, only 9:1 and I run 93 octane at close to sea level. Compression tests are around 170-180 psi. Plus when the cars idling and I stick my head close to the ground outside the door, I hear the ticking, so I think it’s just exhaust noise, not actually pinging.

    I know what a car with exhaust manifolds and more civilian exhaust sounds like when it pings. I’m not sure it’s exactly what I’m hearing. I’m thinking it’s more the thin tube headers making the noise.

    I’ll probably keep adding base timing 2 deg at a time. How will I know when I went with not enough to too much?
     
  7. biker

    biker Veteran Member

    Messages:
    767
    Likes Received:
    55
    Joined:
    Dec 7, 2014
    Location:
    New Liskeard Ontario Canada
    I find even with loud exhaust, I can hear pinging. It is different from other little niggling noises an engine makes. Just takes a bit of load in a tall gear. 16 degrees initial with full manifold vac advance sounds pretty good for a starting point. If you don't have a way of retarding the timing at startup, you have gone too far if it kicks back when hot. Have you measured total timing and at what rpm it stops advancing?
     
  8. biker

    biker Veteran Member

    Messages:
    767
    Likes Received:
    55
    Joined:
    Dec 7, 2014
    Location:
    New Liskeard Ontario Canada
    You old bugger. In got you beat in age, but not experience. I only want to measure spring weights so I can keep a record of what spring has what effect on the curve.
     
    jeff swisher likes this.
  9. 1980RS

    1980RS Veteran Member

    Messages:
    3,153
    Likes Received:
    508
    Joined:
    Jun 17, 2006
    Location:
    MN
    If you have an MSD distributor, put the black spacer in it then one weak and one strong spring in there, next set the timing to 18° and you should be at 38° total. Easy peasy.
     
  10. cadillac_al

    cadillac_al Veteran Member

    Messages:
    826
    Likes Received:
    85
    Joined:
    Apr 22, 2015
    Location:
    Maine
    That's the beauty of vacuum advance. You get lots of timing at idle.
     

Share This Page

  1. This site uses cookies to help personalise content, tailor your experience and to keep you logged in if you register.
    By continuing to use this site, you are consenting to our use of cookies.