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timing curve weights

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by Sparky, Aug 9, 2002.

  1. Sparky

    Sparky 1/2 ton status

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    Where can i get the weights and springs used to adjust the timing curve for an HEI distributor. I just want the factory weights and springs, but no auto parts places carry them.

    The reason i think i need them is because my timeing dosent want to fall back down after it advances. Put a timeing light on the truck today because it was acting funny, and i found that the timeing would varry anywhere between 8 degrees and 16 degrees. It wanted to stick at about 14 degrees BTDC, and then it would slowly fall down to about 10 or 12 degrees. Sometimes it would fall all the way to 8 degrees. So i am thinking either the bearigs in the distributor are worn out or the mechanical advance ist working properly.
     
  2. tipoil

    tipoil 1/2 ton status

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    I would look at the advance plate,it must be sticking a bit
    ,that's why u get "crazy"timing .

    just pull the distributor from the engine and take it apart on the bench,look at the top part of the shaft to see if the triger(star shape thing) will move freely on the shaft, then when evrything is ok,put it back together But remember to lube the triger whit LIGHT oil(if u use something heavy like 20w50 or grease the advance will stick when cold . u could try trany fluid or something else) then evrything should be ok

    if u need a advance kit try: summit,jegs,accel,msd,moroso,and maby more not sure!!
    if u need the "stock"ones try GM
     
  3. Blue85

    Blue85 Troll Premium Member

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    First, In case you didn't, make sure that the vacuum advance is disconnected and line plugged and that the idle speed is low enough (probably <800 rpm) in order to get true timing readings.

    Second, you may not need any parts to fix your problem. The weights are probably just sticking. This is common as crankcase vapors can gum up the distributor over time. You can do the aforementioned lube job with the distributor still in the engine, if you'd like. Take the rotor off and then remove the springs and weights and clean and lube the springs, weights, plate, and the spot where the mech advance pivots on the distributor shaft (you'll see it once you're in there). As long as the holes in the weights are still round, put them back in. While it's open, check to make sure the bushings don't allow side-to side play.

    Third,
    I don't know why you would want to reuse the stock springs. They are so heavy that you really never get full mech advance and it comes in too late. A curve kit is cheap if you can find the kind with only springs. Even with the adjustable vac can, around $20-$24. You probably don't want cheap weights out of a kit anyway. Most will recommend one medium and one heavy spring from the kit. Even heavy is lighter than the stock ones. If you want to be more conservative, use two heavy from the kit. The shape of the weights limits the total mech advance, so lighter springs aren't going to give you more total, just bring it in faster. This gives you better acceleration off the line and in the low end.

    If you still want stock springs, the ones in your distributor are probably fine to reuse. If they are missing or stretched (not likely if you are not pinging) you should be able to get some from a junkyard, but you might have to buy a whole distributor.
     
  4. dyeager535

    dyeager535 1 ton status Premium Member

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    You don't have to totally remove the distributor, I'd personally take the cap and rotor off before pulling the whole assembly out.

    I had mech advance problems, and it was blatantly obvious the problem was the bushings that the mech weights pivot on. There are actually 4 "bushings" for the mech advance (may not be in all applications, Olds only uses two, so Chev might go either way some years?) two for the "pivots" and two that the weights slide on. The ones that the weights slide on seem to pretty much never wear out, and I don't think you can even get those new. The pivot bushings come in the $5 Moroso "curve kit" along with 3 different weight springs, one set of which is touted as being "stock replacement".

    As was said, no reason to really replace the springs, (unless you want to change the way the advance works) I doubt they are bad, just be careful removing and installing them, or you may lose one.

    If the problem ISN'T obvious when you pull the cap/rotor off, I'd then think about removing the whole thing and inspecting it.

    BTW, I believe the Moroso kit comes with weights as well, but again, they are a non-wear part.
     
  5. Blazer_Boy

    Blazer_Boy 1/2 ton status

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    I had the Mr. Gasket and Accel weight kits. They are now sitting in a box of parts. I thought about using the bushings on the stock weights too, but they were too big. You possibly could drill the holes larger to accept the bushings.

    I've noticed in our big ol' pile of HEIs up at the shop that the ones that came out in the later years before computer control and ESC didn't have 4 bushing setup, but 2. So I guess Chevy did that too. I've also noticed that the later weights don't have bushings in them, just a little hardend piece in the hole that can't be removed. Those never seem to wear out, I believe they have "90" or the like stamped on them. One of those super heavy stock springs and a medium type spring from an early model car or points distributor (some points distributors will have the fat spring too) will make a curve that begins right off idle and is in by about 3,000 RPM.
     
  6. dyeager535

    dyeager535 1 ton status Premium Member

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    The dist. I've got is pretty old, so say an '83 or something probably did go with the cheaper/simpler two bushing setup.

    The bushings that came with my kit worked, (2 different types) but one rolled down the driveway, so I had to modify the "thick" bushings so that the weight rode only on the "washer" I had made, and then I used the Olds weights on the Chev dist., so I didn't need the pivot bushing. 10 minute job turned into a 30 minute job, of course. /forums/images/icons/smile.gif
     
  7. Sparky

    Sparky 1/2 ton status

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    Sorry its been so long. I never have anytime these days. Thanks for the info on where to get the weights, bushings, and springs. I guess i will order the Moroso kit, since that seems to be the most complete, or try to find one at a performance shop localy.

    Sparky
     

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