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SB 350 timing tab ?

Discussion in 'The Garage' started by Nonesuch, Feb 27, 2003.

  1. Nonesuch

    Nonesuch 1/2 ton status

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    I have just learned that I have a motor with a top mount (90* straight up from crank journal) timing position (TDC). I never new GM made these and when I installed my timing cover and tab I put one on that hangs on the side. Well after running this for a while I decided it was time to fully tune my motor /forums/images/graemlins/thumb.gif and when I was adjusting the vales (after installing roller rockers /forums/images/graemlins/thumb.gif) I found out this new information from a friend(after making tons of racket being way off TDC /forums/images/graemlins/eek.gif). My question is /forums/images/graemlins/confused.gif, are there differently indexed balancers or is it the crank that indexes the balancer? Or do I just need a new timing cover and tab with 0 TDC on top or do they make a tab that I can get aftermarket that is on top? I am hoping for the balancer because that would be so much easier to replace and I could stand a new one anyways!
    Justin
     
  2. Goober

    Goober 1/2 ton status

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    I ran into the same problem when I had to replace my cover. My old one was injured in a timing chain mishap (that's another story) and I replaced it with a spare I had in my shed that had the timing marks on the side. Luckily, I had the engine on a stand at the time so it was easy to work on. I just got #1 at TDC and pulled out my trusty chisle and made a mark at 0 degrees.

    I usually tune with a vacuum gauge and when I got everything all setup it seemed to be right on the money!


    But, if you can spare the change to buy a new balancer this is a good excuse! /forums/images/graemlins/thumb.gif
     
  3. ZonkRat

    ZonkRat 1/2 ton status

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    Never even heard of that.Would like to think the diff is the balancer.Good luck,shurly someone here can help. /forums/images/graemlins/thumb.gif
     
  4. Lonnie

    Lonnie 1/2 ton status

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    If I remember correctly, there are 7 different combinations of tabs/balancers (including 3 different balancer diameters) for the 1st gen small block. All cranks are keyed the same with the key aligned with #1 TDC. Most trucks use the 8" balancer with the straight up (centered) timing mark (these often have a pickup tube located on the tab as well) or the timing mark indexed in line with the keyway (within a few deg.). If I can find the difference in degrees, I will post this value as you can easily scribe a new mark on the balancer.
     
  5. Nonesuch

    Nonesuch 1/2 ton status

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    This would be a great temp fix for me! I am glad I dont have to pull the front of the motor off just so I can time it with a light. The original reason for all of this was to tune my carb. It is amazing how one project spawns another. I have checked the rubber on my balancer and it is a little worn. I will most likly replace the balancer once I get a few $$. For the time being though, degreeing the line on the balancer myself would work great!
    Justin
     
  6. Nonesuch

    Nonesuch 1/2 ton status

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    I have done the same thing for now(vacuum tuned), but I want to dial this thing in on the money. I have spent the last 7 years doing it in my old half ass ways and I figure its time to start doing everything right, now that I have the time and knowledge! /forums/images/graemlins/thumb.gif
     
  7. Lonnie

    Lonnie 1/2 ton status

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    From what I can find on balancers, the 1968 & earlier have the mark 2 deg before (moving clockwise) the keyway centerline. 69 & later 8" GM performance balancers are 10 deg before the keyway centerline. I do not have the measurement for the late style, but it is somewhere in the neighborhood of 45 deg before the keyway.

    Here is how to quickly locate the new mark.... not 100% accurate due to manufacturing tolerances & measurement error. Carefully measure the outside circumference of the balancer (approx 25") & divide this number by 360. This is the distance for 1 deg (roughly 1/16" so be precise) then multiply by # of degrees offset needed from keyway & mark the balancer. A small sharp triangle file works well.

    You can also locate TDC (preferred method) with a piston stop (a screw in plug for spark plug hole). Screw stop in plug hole. Rotate crank with a wrench until it stops (carefully so you do not break the piston).... mark balancer with a line at TDC on the tab. Rotate crank in the opposite direction until it stops.... make a second mark. Exactly between these 2 marks is exact TDC.

    Hope this helps.
     
  8. Nonesuch

    Nonesuch 1/2 ton status

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    This should definatly help. I was thinking about how to do this out last night and this is alot easier than what I came up with. Thanks!
    Justin
     

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