Register now to get rid of these ads!

Technical Distributor Advance Springs

Discussion in 'Traditional Hot Rods' started by mwhistle, Aug 10, 2018 at 9:41 PM.

  1. mwhistle
    Joined: Feb 19, 2007
    Posts: 274

    mwhistle
    Member
    from sacramento

    In the past, member have had excellent discussions about ignition timing as it relates to distributor advance and the various springs that speed up or retard the distributor advance curve. However, in these discussion I have not noticed examples of why a particular spring was chosen as it relates to the rate (speed) of the advance curve. For example, in drag racing, should a light race car use light springs for quick timing advance versus a stronger spring that lengthens the advance curve rate for a heavier car? In essence, I would like to know what general guidelines members can provide regarding spring advance depending on car weight or camshaft or transmission (manual vs. automatic) or whatever other variables you take into considerations when selecting a distributor advance spring. Any input about which springs work best in different applications would be great. Thank you.
     
    firstinsteele likes this.
  2. Truck64
    Joined: Oct 18, 2015
    Posts: 2,160

    Truck64
    Member
    from Ioway

    Basically you want as much advance as it will stand as early as possible, short of detonation or knock. Heavy trucks designed to haul heavy loads use stiff springs, they aren't done advancing till 4000 or beyond. For street applications tuners will often shoot for "all in by 2500" say, something like that. It gets complicated because compression, fuel quality, altitude, gearing etc all plays a role on how much you can get away with, have to experiment. Drag racing otoh is a different deal altogether. I dunno. I think they just set the initial timing to 36 deg. and call it good. Don't need no stinkin' springs!
     
    Last edited: Aug 10, 2018 at 11:17 PM
  3. Mike VV
    Joined: Sep 28, 2010
    Posts: 1,031

    Mike VV
    Member

    What Truck said (basically).
    Ignition timing is power.
    Get the mechanical all in as soon as possible (before 1500 or 1600rpm). Then adjust the dial in timing (distributor) from there.

    Mike
     
  4. When my friend mike set up his 10 second 455 Olds Vista Criiser he used medium to heavy springs for power band reasons.

    My 455 in a 2,500 lb. Roadster I ran the lightest springs so it spooled up quicker! I really wished I could have dynoed the difference...
     
    Register now to get rid of these ads!

  5. Torana68
    Joined: Jan 28, 2008
    Posts: 886

    Torana68
    ALLIANCE MEMBER
    from Australia

    Needs a dyno and a knock sensor. Some engines like it one way others another. One ot engine I have here liked a dip in advance at a certain rpm . ( certain rpm cause I forget, 3400 on boost I think) Slight retarding at max rpm can also be usefull. Some of these things need electronic advance.
    Just saying there is no one size fits all.
     
    Last edited: Aug 11, 2018 at 3:32 AM
  6. Jimbo17
    Joined: Aug 19, 2008
    Posts: 3,299

    Jimbo17
    Member

    On a small block Chevrolet I have seen between 40 and 42 degrees of timing.
    I know that many believe it should be around 38 degrees.

    Jimbo
     
  7. Joe H
    Joined: Feb 10, 2008
    Posts: 602

    Joe H
    Member

    I set up Pontiac distributors and always go for " all in by 2500 ". The trick is to limit the amount of advance then play with springs to control how fast it gets there. The Pontiac engine has enough torque and power that the weight of the car doesn't really matter. You also don't want the distributor to back off when the transmission shifts, this applies to drag racing mostly.

    Even with will stiff springs, the advance can creep as the rpm's climb, so I braze, or weld, or set screw in solid stops. If the cars have header / starter heating problems, set enough advance so the initial timing can be fairly low to help turn the engine over.
     
  8. Truck64
    Joined: Oct 18, 2015
    Posts: 2,160

    Truck64
    Member
    from Ioway

    I thought dragsters &c basically had a "locked out" distributor?
     
  9. 28 Ford PU
    Joined: Jan 9, 2015
    Posts: 269

    28 Ford PU
    Member
    from Upstate NY

    Joe’s right on. Put a light on it and see when your dizzy stops the mechanical advance. Then put that total mechanical at 36-38. Now see where your advance is at idle, could be between 10-20 and that’s fine as long as it doesn’t kick back when starting.

    If all is good start experimenting with springs with the goal of 36-38 @ 2500 RPM.

    All of this needs to be done with your vacuum line plugged if running a vacuum advance with your mechanical. I’m a Hugh fan of Vacuum advance.

    Good luck.


    Sent from my iPad using The H.A.M.B. mobile app
     
  10. Its called "tuning your application" to provide quick acceleration with no detonation.
     
  11. mwhistle
    Joined: Feb 19, 2007
    Posts: 274

    mwhistle
    Member
    from sacramento

    Thank you all for your suggestions and information. I have an old school fenderless 1931 Model A couple that weighs 2,420 lbs. I run a basically stock 9:1 compression 327 cu. in. 1969 Chevy engine with three Stromberg 97s. A couple years ago I discovered I had more fun at the drag strip than at car shows. When I started, I ran in the mid 15s at 97 mph. Over the past two years, I added 3.25 gears and Tru-Lock to my 9 inch Ford rear end. Along with M/T drag radials, I got into the high 13s. Last winter, I put in a CompCam (256 extreme energy) and got down to 13.24 ET at a little over 101 mph. I'd like to get into the high 12s without doing more engine work or getting better heads. The engine seems to flatten out a little at the top end at the drag strip. I hoped that proper ignition timing (better advance curve) might help; hence my HAMB request for member input which I will use. Thank you.
     
  12. saltflats
    Joined: Aug 14, 2007
    Posts: 8,214

    saltflats
    Member
    from Missouri

    What RPM are you leaving the line?
     
  13. Truck64
    Joined: Oct 18, 2015
    Posts: 2,160

    Truck64
    Member
    from Ioway

    The best thing to do is study the manuals for the basics of operation, and then start experimenting. There's no substitute for either experience nor book learnin'. Every engine is a little bit different, set it up for what works in your application.

    Couple tips: "All In" or "total" timing does not include vacuum advance. So when you see figures like 34° or 36° deg BTDC that's what they mean by that. Also, when the Specifications manuals talk about Timing degrees with respect to distributors, they are half of what actually shows up at the crankshaft, because the distributor runs at half the RPM of the crank.

    Set up the mechanical advance BEFORE ever messing with vacuum, if you have vacuum advance, it needs to be disconnected and plugged when setting the mechanical up. It will require some test drives without vacuum advance hooked up, and depending in design you may have to pull the distributor, disassemble, bend reluctor arms, change spring etc, and re-install. It might sound tedious but that's how it's done.

    When it's running good, THEN re-connect the vacuum advance hose and test drive again for part throttle operation and cruise. No further adjustment should be made to the mechanical advance, make adjustments only to the vacuum canister at this point.

    Or, send the strib off to somebody like Bubba. He can set it up for you on an Allen distributor machine.
     
  14. mwhistle
    Joined: Feb 19, 2007
    Posts: 274

    mwhistle
    Member
    from sacramento

    Thank you again for all comments. To answer a couple of questions, I drive the car to the races so I take it easy and don't leave the line hard. I have a Muncie 4 speed and leave at 2,500 RPM and have very little tire spin with the M/Ts and experience only occasional minor bogging. I do all timing checks with vacuum hose disconnected and plugged. I also use timing tape on my damper based on TDC that I determined through use of a piston stop to ensure true TDC. The car runs very well at all speeds; I'm just looking far a little more top end pulling power. My three very small 97s only give me 480 CFM, so that could be part of the problem but I'm not in a position to install one of the newer style Holly or Edelbrock carbs. I'm simply trying to do better with what I have. Thanks again for all comments.
     
  15. mwhistle
    Joined: Feb 19, 2007
    Posts: 274

    mwhistle
    Member
    from sacramento

    Sorry, I forgot to mention that I use a stock Chevy single point distributor.
     
  16. saltflats
    Joined: Aug 14, 2007
    Posts: 8,214

    saltflats
    Member
    from Missouri

    I keep putting timing in it tell the MPH falls off then back it off for the best MPH.
    At 2500 RPM you should have all advance in.
     
    Truck64 likes this.
  17. Joe H
    Joined: Feb 10, 2008
    Posts: 602

    Joe H
    Member

    Sounds like you are doing every thing right, just keep trying small changes at a time and you will find what works and what doesn't.
     
  18. Truck64
    Joined: Oct 18, 2015
    Posts: 2,160

    Truck64
    Member
    from Ioway

    With 87 octane laced with corn-squeezins?
     
  19. 28 Ford PU
    Joined: Jan 9, 2015
    Posts: 269

    28 Ford PU
    Member
    from Upstate NY

    That’s fine but I personally would get rid of the points system.


    Sent from my iPad using The H.A.M.B. mobile app
     
  20. Truck64
    Joined: Oct 18, 2015
    Posts: 2,160

    Truck64
    Member
    from Ioway

    Well he said he's using a points distributor, not necessarily points. Make sure the end play is in spec and bushings are good regardless.
     
  21. saltflats
    Joined: Aug 14, 2007
    Posts: 8,214

    saltflats
    Member
    from Missouri

    If running points, I would ditch the vacuum advance and lock down the breaker plate so it can't move around. Then install some good points with a heavy spring.
    Then all your advance would be just in the mechanical advance.
     
  22. 28 Ford PU
    Joined: Jan 9, 2015
    Posts: 269

    28 Ford PU
    Member
    from Upstate NY

    Sorry!

    I shouldn’t of said system.

    WOW


    Sent from my iPad using The H.A.M.B. mobile app
     
  23. 6sally6
    Joined: Feb 16, 2014
    Posts: 84

    6sally6
    Member

    On my "souped-up" 66 Mustang I use the light weight springs and have full advance around 15/18 hundred RPM. 36* total advance.(according to the attached timing tape) "BEWARE"....JUST the light springs will let-it-do-what-it-do...meaning you need to limit the total advance or the dizzy will just keep on advancing as RPM increases. (Which ain't a good thing"!) I found(on a Duraspark distrib.) putting a home made spacer on the spring "pin" will stop it at 36-38*. The spacer is a slice of pushrod pushed down on the pin and held in place with epoxy. Perfect thickness.
    The bad part about a FoMoCo distrib is.......all the weights and springs are in the BOTTOM of the distrib. (not the top like "them-damned-old-Shivel-layz") so its a pain in the ear to keep changing springs and limiters. Thickness of the push rod is dern-near perfect!
    6sally6
     
  24. Truck64
    Joined: Oct 18, 2015
    Posts: 2,160

    Truck64
    Member
    from Ioway

    Dude, don't wig out, have to reverse engineer what people say, and troubleshoot remotely. I didn't mean a thing against you by it, just trying to clarify so everybody's on the same page. Who the fuck knows if he's running points or not.
     
    Last edited: Aug 12, 2018 at 8:47 PM
  25. Truck64
    Joined: Oct 18, 2015
    Posts: 2,160

    Truck64
    Member
    from Ioway

    Yep, pita. There is an access hole in the breaker plate though that lines up with the spring arm, designed for adjusting spring tension on the arm with a screwdriver to get earlier advance or later advance in the curve.
     
  26. seb fontana
    Joined: Sep 1, 2005
    Posts: 5,307

    seb fontana
    Member
    from ct

    Realize that at what rpm the advance starts is important..If you idle at say 800 rpm then the advance should not start below 800 rpm but at about 900 rpm and be at in by 2500 or so then work with jets for optimum power..Reason for above idle speed advance start is that if below idle speed you will hunt idle speed all over the place and driving will suck when taking off in first gear..I would do more rear gear also, 4:11 but depending on what your max rpm is.....
     

Share This Page

Register now to get rid of these ads!

Archive

Copyright © 1995-2013 The Jalopy Journal: Steal our stuff, we'll kick your teeth in. Terms of Service. Privacy Policy.

Atomic Industry
Forum software by XenForo™ ©2010-2014 XenForo Ltd.