Dismiss Notice

Welcome To CK5!

Registering is free and easy! Hope to see you on the forums soon.

Score a FREE t-shirt and membership sticker when you sign up for a Premium Membership and choose the recurring plan.

How much Timing advance???

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by Burt4x4, Mar 1, 2000.

  1. Burt4x4

    Burt4x4 3/4 ton status

    Joined:
    Feb 17, 2000
    Posts:
    6,854
    Likes Received:
    0
    Location:
    California (Modesto area)
    I have a 350 bord30over, TRW Flattop pistons,RV type cam,194Heads,Edelbrock Performer intake, Edelbrock 750cfm Q-jet,MSD 8360 dist.,Blaster coil,Headman headers,K&N filter.

    With this type of engine, what should the initial timing be set at?? 4 ,8 ,10 ,??
    After that I can switch the springs on my dist. to allow the mechanical advance to advance in a quick manner or a slower type of advance curve.
    Does anyone know what the TOTAL advance should be at a particular RPM???
    Oh and the VAC advance should be pluged while I do this,right??
    Any thought on this would be GREAT!!
    Burt4x4

    Rock ON!
     
  2. Depdog

    Depdog 1/2 ton status Author

    Joined:
    Feb 17, 2000
    Posts:
    1,657
    Likes Received:
    0
    Location:
    Georgia
    Well, my book on my 77 model says to disconnect and plug the vacume advane. Set the idle at 750 to 800 rpms and set to 8 degrees.

    Got to advance it some, have spark knock, but its a start for ya.

    Depdog

    <font color=blue>"Lead, Follow, or BECOME the Trail"</font color=blue>
     
  3. Matt N.

    Matt N. Registered Member

    Joined:
    Feb 17, 2000
    Posts:
    24
    Likes Received:
    0
    Location:
    Seattle WA
    Easiest thing to do is find a local speed shop, tell 'em what you got, and give 'em your distributor. They should have enough experience to curve it appropriately. I have had little luck with the cheesy advance kits in the past, have not been happy at all. A good shop does it better. Remember- when it comes to spark advance, more is NOT better.
     
  4. Burt4x4

    Burt4x4 3/4 ton status

    Joined:
    Feb 17, 2000
    Posts:
    6,854
    Likes Received:
    0
    Location:
    California (Modesto area)
    The MSD comes with color coded springs and a chart that tells you what the different color combinations will do to the mechanical advance curve.
    I'm just tring to figure out what is the best curve to use for a 350 built for low RPM use(idele to 5000).
    Do I want the advance to jump up there fast or more of a gradual climb as the RPM increases??
    anyhoo I am gona be goin thru it all this weekend to try and fix my POP....POP and hesitation issue.
    Thanks for all ya'alls input!
    Burt4x4

    Rock ON!
     
  5. delta9blazer

    delta9blazer 1/2 ton status

    Joined:
    Feb 17, 2000
    Posts:
    1,646
    Likes Received:
    0
    Location:
    Northern California, over by 7-11
    5000RPM's is not low for a V-8 with 2-valve heads.
    thats low rpm for my old ninja, maybe.........

    <font color=purple>delta9blazer</font color=purple>
     
  6. Jay73K20

    Jay73K20 Registered Member

    Joined:
    Mar 4, 2002
    Posts:
    67
    Likes Received:
    0
    I would start with 10 degrees inital timing @750 rpm and 36 degrees total timing @3000 rpm. If it dosen't detonate try 12 degrees initial and that will change total to 38 degrees and if you can't feel a difference at 38 versus 36 then change it back to 36. If it detonates when you accelerate at the 3000 rpm range then increase spring strength so total timing comes in at about 3400 rpm. When you adjust your timing disconnect your vacuum advance.

    Jason
     
  7. BorregoK5

    BorregoK5 1/2 ton status

    Joined:
    Sep 7, 2001
    Posts:
    2,457
    Likes Received:
    0
    Location:
    San Marcos, Ca USA
    I just recurved my ignition, actually several times trying different methods. Your specific total advance will vary due to all kinds of variables (cam, weight, intake manifold, mixture .. etc). Disconnect your vacuum advance and set your initial timing at 10 deg. Take it for a spin and load up the motor up hills through the rpm band, make sure to test it in 2nd and third gear as well. If you get any detonation then back it off 2 degrees and try it again. If you dont get any detonation then swap a step lighter spring onto your mechanical advance and repeat the steps above. If you get detonation at 8 degrees then swap a heavier spring onto your mechanical advance, etc. Your goal should be to have no detonation (part throttle or full throttle) at 8 deg (+/- 1) initial advance (assuming your daily driving / weekend warrior). Now plug in your vacuum advance. Your only going to be able to make use of up to 32 deg total advance with an RV cam, most likely less. Take it for another spin and check for detonation (most likely part throttle ping). If this is the case then you should pick up an adjustable vacuum advance (if not already equipped) and finish dialing in the rest of your advance. I'd recommend one with a limiting plate so you can control total advance as well as rate of advance. Sounds like a stout setup you've got!
     
  8. POWERMAD

    POWERMAD 1/2 ton status

    Joined:
    Mar 4, 2001
    Posts:
    3,466
    Likes Received:
    0
    Location:
    Oregon
    Here is a link to a good write up on setting up an HEI.
    <a target="_blank" href=http://www.73-87.com/garage/hei.htm>click</a>
     

Share This Page