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235 timing advice

Discussion in 'The Hokey Ass Message Board' started by muttomatic, Aug 9, 2009.

  1. Howdy folks,

    I've got a '61 Bel Air with a 235 that's giving me fits. I had the timing set to 15 degrees ATDC like the ol' manual says and I think it may have slipped a bit the other day(not that it ran that great with timing set according to factory spec for a powerglide). Idles and starts just fine, but trying to accellerate and maintain highway speed it sputters and farts like a demon. I suspect the dizzy has slipped and I probably need to attempt to adjust the vacuum advance...

    Seems to me 15 degrees ATDC isn't really the best setup for this thing. Has anyone blocked off the vacuum advance and could the tell me their results? Should it be close to TDC? Or 5 degrees BTDC for a manual tranny(like the manual says? Just getting frustrated with poor performance and worse gas mileage.

    Any and all advice is appreciated.

    btw, carb has fresh rebuild and I installed a pertronix and ditched the points.

    Thanks,

    Mutt
     
  2. Got a service manual for a '60 Biscayne. Basically, for the car it came out of.

    Adjusted it to where the ball was top dead center. Ran pretty damn good, took out on the highway and scared the hell out of some folks. Came back and adjusted it a little past top dead center. About 5 degrees. Took the car back out. Ran like absolute ass.

    Came back to the garage, threw the timing light back on and the ball was nowhere to be found. Adjusted it to the ball at TDC and the engine sputtered and died.

    Think the dizzy jumped a tooth???

    Never seems to read the same way twice.
     
  3. 29nash
    Joined: Nov 6, 2008
    Posts: 4,544

    29nash
    BANNED
    from colorado

    No motor has ignition time after TC....................
     
  4. Snarl
    Joined: Feb 16, 2007
    Posts: 1,639

    Snarl
    Member

    BTDC...

    59-62 are all timed to the first short vertical line clockwise from the ball in the flywheel.

    note that the idle rpm is 425-475 in drive and warmed up. Lining up the marks at 450 rpms isn't the same thing as lining them up at 1200 rpms....

    Changing the timing usually means adjusting the throttle setting as well. the two go hand in hand.

    If you were able to get it to run good at a particular setting, why did you change it??

    When you have the timing light on it, does the mark jump around alot, or is it steady?

    The timing gears are just that, a pair of gears. No chain. I have seen the camshaft slide back out of the timing gear, but not jump a tooth. If you pull the dizzy and the cam gear is centered in the hole, you shouldn't have an issue with this.

    While you may be having a parts issue with something, it sounds like you need to get a handle on the whole timing thing first...
     

  5. wood470
    Joined: May 21, 2008
    Posts: 226

    wood470
    Member

    sounds like somethins loose. Could be the bushings are way worn,or point plate is worn out. Somethins movin in there.
     
  6. Yea, in hindsight I wish I hadn't tried to make it "a touch better". I'll pull the dizzy tomorrow afternoon and see what's up with that, if anything.

    Hopefully I'll get it back like it was.
     
  7. " It's been years since I screwed with a 235, isn't the dist. the kind where the vacuum turns the entire housing?"

    Yea, I'm used to old VWs... no vacuum advance... definitely a learning curve on that thing.
     
  8. Snarl
    Joined: Feb 16, 2007
    Posts: 1,639

    Snarl
    Member

    Yes, the advance turns the whole thing.

    Some people have had 235's with worn out dizzys, i.e. sloppy shafts.

    If that were the problem I would expect it to be bad all the time, but you said that you did have it running fine at one particular setting?? so I'm not totally convinced at this point that you have a bad dizzy, other than perhaps needing a general tune up.


    Do you have a vacuum guage?
     
  9. Road Runner
    Joined: Feb 7, 2007
    Posts: 1,256

    Road Runner
    Member


    The 59/60 passenger car shop manual recommends 5º BTDC for both standard and automatic equipped 235 ... http://chevy.oldcarmanualproject.com/shop/1959_60/59sms0704.htm

    That was the factory setting for lower compression ratios matching lower octane gasoline available at the time. Today's gas has higher octane and we have to advance timing a few degrees further for a more complete burn. Timing also depends on your altitude, engine mods and to some extend your driving.

    Easiest and safest way to find your particular ideal timing, is to listen for ping when shifting into high gear on a moderate incline at wide open throttle.
    Advance the timing in small increments until you can hear slight ping, then retard the timing until ping just disappears and a little more.
    This will give you a safe setting, which under max. load still won't hurt your pistons from pre-ignition or worse detonation if advanced too far.

    After that you can read the timing degrees with a timing light and write them down for future reference.
    If you have a stock engine, you can compare with the manual specs if you are curious.

    Of course you first need a good distributor without play that is clamped tight and a steady flywheel under the timing light.
     
    Last edited: Feb 7, 2010
  10. Vacuum line was crap. I think it was the original. Replaced and running like a top.
     

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