Welcome to Club Hot Rod!  The premier site for everything to do with Hot Rod, Customs, Low Riders, Rat Rods, and more. 

  •  » Members from all over the US and the world!
  •  » Help from all over the world for your questions
  •  » Build logs for you and all members
  •  » Blogs
  •  » Image Gallery
  •  » Many thousands of members and hundreds of thousands of posts! 

YES! I want to register an account for free right now!  p.s.: For registered members this ad will NOT show

 

Thread: Setting initial timing on 350 with no vacuum
          
   
   

Reply To Thread
Page 1 of 2 1 2 LastLast
Results 1 to 15 of 22
  1. #1
    richmondb is offline CHR Member Visit my Photo Gallery
    Join Date
    Oct 2004
    Location
    Jacksonville
    Car Year, Make, Model: 1972 Chevy Chevelle
    Posts
    56

    Setting initial timing on 350 with no vacuum

     



    Okay guys. I need some help setting my timing up on my Chevelle. First let me tell you about the engine. I have a 350 bored .30 over with a Comp Cams XE268, World Products SR 68cc heads, and a Mallory unilite distributor. I just bought my first timing light and am trying to get this newly rebuilt engine running smooth.
    There are 3 different curves I can choose from depending on where my vacuum advance is hooked up: the carb, the intake manifold, and plugged. Here are my curves under the 3 conditions:

    Plugged:
    800: 10 degrees
    1000: 11 degrees
    1600: 22 degrees
    2000: 28 degrees
    2600: 31.5 degrees
    3000+: 36 degrees

    Hooked up to the manifold:
    800: 34 degrees
    1000: 35 degrees
    1600: 47 degrees
    2000: 52 degrees
    2600: 56.5 degrees
    3000+: 60.5 degrees

    Hooked up to the carb:
    800: 10 degrees
    1000: 11 degrees
    1600: 43 degrees
    2000: 50 degrees
    2600: 56 degrees
    3000: 58.5 degrees
    3600+: 60 degrees

    My question is which one do I use, and what should I adjust the distributor to? As you can see I don't have much vacuum from the carb at low RPM.

    Any help would be greatly appreciated.

  2. #2
    TyphoonZR's Avatar
    TyphoonZR is offline CHR Member Visit my Photo Gallery
    Join Date
    Dec 2003
    Location
    Chwk
    Car Year, Make, Model: 86 S-15 Jimmy sb 400
    Posts
    579

    First off, you want to set your timing with the vacuum disconnected. Then depending on the amount of timing advance in the distributor, you go from there, but in any even, you do not want more than 38 degrees total timing at 3000 = rpm. This could mean that at idle it is 16 degrees. You want to be carefull not to have more than 38 degrees at full throttle.

    I always hook up my vacuum at the manifold. In this way at light throttle I have plenty of advance for throttle responce and smooth idle but at full throttle I have no vacuum advance, just mechanical and in this way I am ensured no predetination.

    Hopefully that helps, we'll see what light some others can shed on this topic.
    Objects in my rear view mirror are a good thing unless,.... they have red and blue lights flashing.

  3. #3
    nitrowarrior's Avatar
    nitrowarrior is offline CHR Member Visit my Photo Gallery
    Join Date
    Mar 2007
    Location
    Mesa
    Posts
    1,385

    Have you actually fired it with a timing light hooked up? Numbers seem out of line for your setup.
    What if the "Hokey Pokey" is what it's really all about?

  4. #4
    richmondb is offline CHR Member Visit my Photo Gallery
    Join Date
    Oct 2004
    Location
    Jacksonville
    Car Year, Make, Model: 1972 Chevy Chevelle
    Posts
    56

    Yes I fired it up with the timing light hooked up. That's the way the timing light instructions had me do it.

  5. #5
    richmondb is offline CHR Member Visit my Photo Gallery
    Join Date
    Oct 2004
    Location
    Jacksonville
    Car Year, Make, Model: 1972 Chevy Chevelle
    Posts
    56

    I capped off the vacuum lines and adjusted the initial to 18 degrees at 650 RPM with 45 degrees all in at around 3000 RPM.

  6. #6
    jerry clayton's Avatar
    jerry clayton is offline CHR Member Visit my Photo Gallery
    Join Date
    Feb 2006
    Location
    Bartlett
    Posts
    6,831

    Make sure you use 87 octane

  7. #7
    richmondb is offline CHR Member Visit my Photo Gallery
    Join Date
    Oct 2004
    Location
    Jacksonville
    Car Year, Make, Model: 1972 Chevy Chevelle
    Posts
    56

    My compression is around 9.5:1 so I use premium and it doesn't ping. Can I use too high of an octane?

  8. #8
    richmondb is offline CHR Member Visit my Photo Gallery
    Join Date
    Oct 2004
    Location
    Jacksonville
    Car Year, Make, Model: 1972 Chevy Chevelle
    Posts
    56

    Should I leave it capped off?

  9. #9
    richmondb is offline CHR Member Visit my Photo Gallery
    Join Date
    Oct 2004
    Location
    Jacksonville
    Car Year, Make, Model: 1972 Chevy Chevelle
    Posts
    56

    At 10 degrees I don't get as much punch at take off as I do with 18 degrees. I was reading one of the old forums where it said I should have 16 to 18 initial.

  10. #10
    pat mccarthy's Avatar
    pat mccarthy is offline CHR Member/Contributor Visit my Photo Gallery
    Join Date
    Apr 2005
    Location
    bay city
    Posts
    10,546

    the vacuum should not be bad? low is 2or4 going to a lighter spring will help with the punch i would not run 16 on the crank try 10 to start you want all of it in at 3000 or less .with out vacuum pull hook up and adjust the pull were you want it
    Last edited by pat mccarthy; 10-22-2007 at 04:57 PM.
    Irish Diplomacy ..the ability to tell someone to go to Hell ,,So that they will look forward to to the trip

  11. #11
    35Mastr's Avatar
    35Mastr is offline CHR Member Visit my Photo Gallery
    Join Date
    May 2007
    Location
    Newark
    Car Year, Make, Model: 35 Master Sedan,29 Pontiac 6-29 coupe
    Posts
    63

    I dont want to hijack the thread.But have some ? myself.I have been reading along here and am a little confused on this timing issue.I am also running a sbc 350 stock motor with and edelbrock 650 carb and a ready to run MSD dist.No box.If I set the timing to 16 with the advanced on the dist disconnected.Then connect it after thats done. I had 36 at idle@650RPM.Is this correct.
    George

  12. #12
    krazziee is offline CHR Member Visit my Photo Gallery
    Join Date
    Dec 2006
    Location
    Inman
    Car Year, Make, Model: 1979 Pro Street Camaro
    Posts
    33

    like the man said ........ no more than 38 degrees total advance above 3000 RPM all the way up to full throttle , it should give total advance by 3000 RPM, the rest would be in the dist. with the weights and springs to get it to crank easy and have the advance curve that you want , that is my understanding of it and that is what I do. It seems to work well for me.

  13. #13
    richmondb is offline CHR Member Visit my Photo Gallery
    Join Date
    Oct 2004
    Location
    Jacksonville
    Car Year, Make, Model: 1972 Chevy Chevelle
    Posts
    56

    So according to that, I should dial it back to 10 degrees at idle and plug the vacuum advance and not even use it so I have 36 total all in at 3000?

  14. #14
    TyphoonZR's Avatar
    TyphoonZR is offline CHR Member Visit my Photo Gallery
    Join Date
    Dec 2003
    Location
    Chwk
    Car Year, Make, Model: 86 S-15 Jimmy sb 400
    Posts
    579

    Richmondb,
    1. start your engine,
    2. disconnect the vacuum,
    3. set the timing at 38 degress at 3000 rpm
    4. bring the engine to an idle and see what the timing is
    5. connect the vacuum.
    Objects in my rear view mirror are a good thing unless,.... they have red and blue lights flashing.

  15. #15
    skids72's Avatar
    skids72 is offline CHR Member Visit my Photo Gallery
    Join Date
    Dec 2005
    Location
    Lafayette
    Car Year, Make, Model: 68 Firebird 439 BBC
    Posts
    745

    I won't say 38* max is a hard fast rule, but 45 total mech (i.e. not vac) is really high for your application. I have run up to 42* on pump premium at 10.2:1 compression but I'm at high altitude and can get away with it.

    I think for your application 36* total, probably around 12* on the crank is a very good starting point and you can tweak from there.

    -Chris

Reply To Thread
Page 1 of 2 1 2 LastLast

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
Links monetized by VigLink