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Play in the distributor

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by Blue85, Jul 26, 2002.

  1. Blue85

    Blue85 Troll Premium Member

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    What kind of "play" is normal in a distributor. I can turn my rotor backwards by hand about 1/10 of a turn. It moves up in the air while I do this, as it seems to be the distributor gear walking up the cam gear. This is not the movement of the rotor with the mechanical advance, it is movement of the distributor shaft. How much play like this is acceptable?
     
  2. dyeager535

    dyeager535 1 ton status Premium Member

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    Hmm, I'd guess that 1/10th of a turn is excessive. (and hard to judge lol)

    Usually it's measured with endplay on the gear end, (obviously out of the vehicle) and its not very much, something like .080 or something? Total guess, but that number is sticking in my head. That measurement might be in the manual. You'd have to have a fair amount for it to actually "climb" the cam gear though!

    Someone (moroso?) makes a shim kit for the distributor, to fix endplay. Local speed shop carries it.
     
  3. Grim-Reaper

    Grim-Reaper 3/4 ton status Author

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    You really can't judge it that way. You have a mechanical advance in the mix if your grabbing the rotor button to test. there is also some play in the drive gear as well as any play in the chain on the cam. I believe the cam is going to pull down on the distributor when it's driving it so the fact that it comes up when you turn it backwards is not an issue. What your looking for when inspecting a distributor is side to side movment from the bushings being worn out on the shaft. Then remove it and inspect the gear for any unusual wear on it. Check that the mechanical advance works smooth and returns to it's rest spot. quickly with no drag.
    Often oil vapors will coke on the inernal shaft and hang the mechanical advace causing timming problems. Easily fixed by driving the roll pin out of the gear, remove the springs and weights for the mechanical advance and it will slide appart. Then you can clean the internal shaft. Grease it lightly with a high quality high heat grease.
    The test that you might want to perform is to rotate the crank by hand to TDC. Mark where the distributor is pointed then turn the engine backwards till the distributor starts to turn. Look at the timming mark on the ballancer and see how many degrees you had to turn the engine on the timming mark tab. 5degrees is ok because there will be a little slop in the distributor gear and a little in the chain. If your up around 10 your timming chain has excesive slack in it. It will cause your timming to be erratic on both valves and ignition.
     
  4. Blue85

    Blue85 Troll Premium Member

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    I'm grabbing it with the rotor off, on the part that's tied to the shaft, below the mechanical advance. It can't move much without raising up, so maybe that it OK? I can't move it much side to side. The mechanical advance is in good shape, as I just cleaned it, lubed it and put in new springs. Plus, I checked with a timing light and the timing is changing from about 900 to 3000rpm.
     
  5. Grim-Reaper

    Grim-Reaper 3/4 ton status Author

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    Sounds like it's fine then. Run with it if the mechanicanical advence is not hanging that's what you whant to make sure of.
     
  6. Blue85

    Blue85 Troll Premium Member

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    Thanks for the lowdown. Now that I've timed everything, it seems like everthing happens the way it should, so I feel better. At least engines don't have to run backwards!
     

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