Which points for 1973 lesabre 350 - napa part did not work, put old back in works??

Discussion in 'Small Block Tech' started by garybuick, Jun 13, 2013.

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  1. LARRY70GS

    LARRY70GS a.k.a. "THE WIZARD" Staff Member

    Re: Which points for 1973 lesabre 350 - napa part did not work, put old back in works

    Actually, no they aren't, but they are related. The dwell angle is the amount of distributor rotation, in degrees, that the points are closed. It's important to remember that dwell affects timing, but timing does not affect dwell. Dwell shouldn't vary more than 3* maximum. If the distributor shaft bushings are worn, the shaft can wobble, and dwell will be all over the place. remember, dwell affects timing.
     
    LARRY70GS, Jun 14, 2013
    #21
  2. CJay

    CJay Supercar owner Staff Member

    Re: Which points for 1973 lesabre 350 - napa part did not work, put old back in works

    For the record, "dwell" is actually dwell angle. Its the amount of degrees that the points are closed. Point gap is the actual air space between the two contacts.

    Setting point gap is the preliminary setting. After the engine starts, dwell is adjusted as a fine tune. And remember that dwell effects timing. So the timing must be checked after dwell is set
     
    CJay, Jun 14, 2013
    #22
  3. garybuick

    garybuick Time Traveler

    Re: Which points for 1973 lesabre 350 - napa part did not work, put old back in works

    are not dwell and gap both set with the same screw?
     
    garybuick, Jun 14, 2013
    #23
  4. CJay

    CJay Supercar owner Staff Member

    Re: Which points for 1973 lesabre 350 - napa part did not work, put old back in works

    Yes, but they refer to two different things
     
    CJay, Jun 14, 2013
    #24
  5. garybuick

    garybuick Time Traveler

    Re: Which points for 1973 lesabre 350 - napa part did not work, put old back in works


    when dwell is changed, gap is changed, cant change dwell without changing gap can you? cant change gap without changing dwell can you? The relationships between gap and dwell are always the same are they not? How many degrees of distributor shaft rotation take place while the points are closed is determined by how big the gap is, is it not? Depnding on the size of the gap, the distributor can turn a certain number of degrees before the gap opens, the bigger the gap the more degrees it can turn before the gap opens. We set the gap, the result is the dwell. We dont set the gap and then set the dwell, we set the gap and then fine tune the gap, or we set the dwell and then fine tune the dwell, its the same exact thing. Shouldnt have to put a breaker bar on the balancer to install points, something wrong with that picture IMO.

    Having said all that, I am now going out to the garage and see and I hope I am wrong because it will save me a trip to the parts store and the awkward tension that takes place when you return something. Besides if it doesnt work and I have to return it, if they say I need to set the gap to start the engine i can say I actually tried that.

    ---------- Post added at 02:21 PM ---------- Previous post was at 01:20 PM ----------

    Considering that new points may not be even ballparked anymore, I set the points all the way in and tried it, no spark, then set the points all the way out, wouldnt start, then set them halfway and it started right up, then I set the dwell to 30 deg with the dwell meter. From now on thats what Ill do, just set the points to the middle of their travel range, install, start engine and set with dwell meter. Then i set the timing using the vacuum method. I just got it up to temperature and then plugged the vac advance with vaccuum gage and turned the distributor until I got max vacuum with smooth idle. Running good now, it does rattle a little on full throttle from a stop sign. I put weaker springs in it also a while back. For some reason there is not enough travel in the distributor turning it to get the timing with vac advance disabled to less that 12. So the points are good after all and do now need to be adjusted to get the engine to start, the old days are over.
     
    garybuick, Jun 14, 2013
    #25
  6. LARRY70GS

    LARRY70GS a.k.a. "THE WIZARD" Staff Member

    Re: Which points for 1973 lesabre 350 - napa part did not work, put old back in works

    I can't believe you want to go back and forth about dwell angle:laugh: They are not the same thing by definition, but as I said, they are related. Change the gap, you change the dwell, and visa versa. Now that that is settled (hopefully:grin:), it is important to check the gap when you install points. I find it easier to use a breaker bar and turn the engine to get the rubbing block up on the high point of the distributor cam. Some guys like to bump the starter, personally, I think my way is faster, but do whatever works for you.

    Now we get to the "Vacuum method" of setting your timing. That is a very bad idea. Why? Because it doesn't take into account the mechanical and vacuum advance in the distributor. The highest vacuum will tell you where the engine likes to be as far as initial timing goes, and frequently, that will be at least 10-12*BTDC. But what if you have a distributor that has 30* of mechanical advance in it? Now when you nail it, you are at 42*, and then add in the 16-18* of vacuum advance at cruise, and maybe you are at 60*BTDC, but at that point, you might be surging, and wondering what is wrong. All distributors are different. They have differing amounts of mechanical advance built into them. This varies with year, and engine size. Also, distributors get changed over the life of a vehicle, so it's important to make sure you know what you have. That is why I constantly stress that if you want to set your timing, set the total timing. Your initial will then be where it MUST be for your particular distributor, and the total advance you choose to run. You can't just run any initial you want, and call it a day. I mention this in the first post of my Power Timing thread. If you want to determine what initial timing your engine likes by using the vacuum method, that's fine, but check the total to make sure you aren't over advancing. Engines will rattle and worse when you do that. If you determine that your engine likes 14* of initial timing, but your total is too high, then you must reduce the amount of mechanical advance in the distributor. In a points distributor, you may be able to use a bushing to limit the mechanical advance. There may already be one there. In that case, you have to remove the distributor, disassemble it, and modify it. Again, this is all covered in the Power Timing thread.

    http://www.v8buick.com/showthread.php?63475-Power-Timing-your-Buick-V8

    BTW, if you run out of distributor travel before you can set the timing to what you want, it means the distributor is in a tooth off. Nothing wrong with that, timing is timing, but if you don't have the travel to adjust, you have to remove the distributor and put it in on a different tooth..
     
    LARRY70GS, Jun 14, 2013
    #26
  7. Fox's Den

    Fox's Den 355Xrs

    Re: Which points for 1973 lesabre 350 - napa part did not work, put old back in works

    The correct way to set the point gap dwell whatever you want to call it is you set the point gap first at about .16-19 start the engine and fine tune the dwell to 30 degrees.

    Larry has it right and I actually had never heard of the trick of just turning the screw 1/2 turn to preset the gap because I always used the feeler gauge to set this first. I actually remember buying a good feeler gauge set to do this right.

    You just can't expect to bolt the darn things in there and expect the car to start. Maybe the new condenser is bad I did run into that one.

    Then I went out and bought a dwell meter to really get the gap fine tuned and if you wanted to you could try to set the dwell at 29 or 31 because sometimes that is just where the car ran better but you have to set the "gap" first before the dwell meter is used.

    On another note I always used the separate point and condenser set, they just worked better.
     
    Fox's Den, Jun 14, 2013
    #27
  8. garybuick

    garybuick Time Traveler

    Re: Which points for 1973 lesabre 350 - napa part did not work, put old back in works

    normally you just install the new set and it starts right up, then break out the dwell meter and dial it in. This is the first time I ever had to do anything to the new points to get the engine to start. I am very surprised and also thankful to larry hate to say for saving me a trip back to the parts store where I would have been publicly humiliated and denied a return. Thanks to all who chimed in.
     
    garybuick, Jun 14, 2013
    #28
  9. 65specialconver

    65specialconver kennedy-bell MIA

    Re: Which points for 1973 lesabre 350 - napa part did not work, put old back in works

    You've been lucky over the years doing it that way.Glad to see you have it running again!:beer
     
    65specialconver, Jun 15, 2013
    #29
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