Register now to get rid of these ads!

timing issues

Discussion in 'The Hokey Ass Message Board' started by wristpin, Apr 12, 2010.

  1. wristpin
    Joined: Aug 31, 2009
    Posts: 48

    wristpin
    Member

    I've posted a few times about trying to figure out why my SBC 400 was twisting off the starter bendix. since i put this motor togeather this has plagued me until recently. it's a stock motor w/ a 288 blazer cam, old edelbrock manifold, topped w/ a 1406 edelbrock carb. everything is swapmeet special stuff. down at the flea mkt. yesterday i got a $5.00 timing lite that i have been needing since the motor build. when i first got it goin i static timed it and then tweaked it till i got it to keep from breakin bendixes off. I timed it to 12' btdc and it runs like shit. had to raise the idle again, but this time she would backfire, surge and run 25 degrees hotter than before. i made sure that the harmonic balencer was on by bring #1 to tdc and the mark was on 0. so i figure that i must be runnin to lean and do a plug check and it's not runnin lean. should i try to get it to run right by the timing #s or bring the timing in to where it runs at 185 degrees all day long a up to maybe 200 when ideling in traffic? all's i know now is that it's been starting every time lately and haven't put a bendix in over a month.one thing i did notice is that when i started off and it was runnin good, the timing mark was above the degree scale and moved down, and in turn run worse.
     
  2. This situation screams of either having a slipped outer balancer ring or incorrect timing tab...there are several different ones. From what you've described, it sounds as if you are having issues before the centrifugal advance even begins to come in. (And, you are disconnecting the vacuum advance before you check the timing, right?)

    As 440 asked, how did you determine that the mark is correct?
     
  3. wristpin
    Joined: Aug 31, 2009
    Posts: 48

    wristpin
    Member

    took out #1 plug and rotated motor until it came up to TDC, at TDC the mark on the H balancer was on 0.
     
  4. Were you using a piston stop?

    Not trying to be snotty...it's just that "visual" TDC usually isn't. I've had one guy get totally pissed at me because I doubted that his method was working. I finally had to prove to him that his balancer ring was about 5 deg. off, but he couldn't tell because TDC wasn't where he thought it was.

    Another possibility is that the timing tab is for a different diameter of balancer...TDC was in the correct place, but the spacing for the marks was incorrect.

    I've seen degreed balancers be off as well...not your problem here, but it happens.

    I've also seen many timing lights that had issues.

    More food for thought....
     

  5. BadgeZ28
    Joined: Oct 28, 2009
    Posts: 1,111

    BadgeZ28
    Member
    from Oregon

    Just a couple comments. 12 DBTDC is a lot of initial timing. You can run it if you have limited distributor advance. These 400 small blocks need a lot of cooling capacity and when you build power, that becomes a bigger factor. My guess is the starter problem has to do with both motor timing and depth of the starter gear.
     
  6. mac762
    Joined: Jun 28, 2007
    Posts: 676

    mac762
    Member

    12 degrees is not a lot of initial timing. I use 16-18 at idle, and 34-36 at 3000rpm.
     
  7. Mac762 is right,,,12 degrees is not too much.

    Tommy
     
  8. Russco
    Joined: Nov 27, 2005
    Posts: 4,194

    Russco
    Member
    from Central IL

    12* can be alot of initial it depends on the specifics of the engine I run 22* initial on my blower motor however it wont crank without a starter timing retard box.
    but something does sound fishy, (it should run at 12* it might not be ideal but it should run) and if your mechanical advance is ballpark you should have around 34-36 total and it should run there as well
    I would suggest going back to the basics and start over verify TDC with a piston stop and mark your balancer for 34 degrees to see whats going on with your advance curve also just to be safe verify all your plug wires to firing order if all that checks out ok id start looking into starter mesh with flywheel
     
  9. BadgeZ28
    Joined: Oct 28, 2009
    Posts: 1,111

    BadgeZ28
    Member
    from Oregon

    I guess I over generalized. Running 16-18 initial and 34-36 total means your distributor only advances 18 degrees, or you are seeing some advance at idle. I time my motors at total degrees also, but have more advance in the distributor. I know with drag racing, automatic cars like a lot of initial timing. I also have a late model with a supercharger and the timing drops to around 16 total advance when it goes into boost. So the variable here is the amount of total advance provided by the distributor used on his 400.
     

Share This Page

Register now to get rid of these ads!

Archive

Copyright © 1995-2021 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.