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Here's one for the small block experts:

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by Blue85, Aug 23, 2000.

  1. Blue85

    Blue85 Troll Premium Member

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    Here\'s one for the small block experts:

    Can you tell me what is going on? I have an 85 with the factory 305 which was replaced with a 350. There is something very strange about the timing or the timing marks. With the vacuum advance disconnected and plugged and the engine idling in gear at about 600rpm, the timing mark shows up about 50 or 60 degrees ahead of where it should be. This is with the timing light connected to the #1 plug wire. The wires are in the order shown by the Haynes manual. I tried the timing light on every plug wire and none of them are anywhere near the timing mark. The engine runs really good, so I'm not suspicious of serious problems and I've had it this way for two years with no ill effects. One time I timed it so that the timing light showed it at about 16 degrees advance, but then the truck would barely run. It had no power and sputtered and blew smoke all the time. Does anyone know what is up with my engine?

    One idea that I have is that the balancer is not keyed right for the crank, so it is off by 90 degrees or some fixed amount. Since the engine is running good, there must be fire in the hole at the right time. With that thought in mind, and since I would like to be able to actually check/adjust my timing, I want to find out exactly where TDC is and put a new mark on my balancer or move the timing tab. In the process of locating TDC exactly, I would solve once and for all whether the timing is reading correctly or not. Does anyone know of a good way to find TDC #1 beyond just feeling for pressure in the spark plug hole? I would like to be able to find it within a couple of degrees without removing the head.

    Thank you for your replies

    '85 JIMMY
    '90 paint/grill/trim 5"susp 33/12.5/16.5
    Fresh 350 B&M '87 TH700
     
  2. Blazer1970

    Blazer1970 1/2 ton status

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    Re: Here\'s one for the small block experts:

    There are two different positions that were used on SBC balancers for TDC. It sounds like you have the timing cover / pointer for one position, and the balancer for the other. It is also common for the outer wheel on the balancer to spin on the hub. There is a device made that screws into the spark plug hole, that will block the piston on its up-stroke. Screw it in, turn the motor (by hand!), until it hits the stop, mark the balancer. Then turn the motor the other way until it hits the stop, and mark this position on the balancer. Halfway between the two marks is true TDC.

    Tim

    1970 Blazer CST 4X4 350 SM465 NP205
    1987 Suburban 4X4 350
    1988 Chevy Pickup 4X4 350
     
  3. Wheels

    Wheels 1/2 ton status

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    Re: Here\'s one for the small block experts:

    Bingo. The two different timing covers are identified by the timing pointers. One has it to the right side (towards the top) of the balancer (looking at the balancer) and the other you have to look down between the block and the water pump to see it. Each requires it's own harmonic balancer that has a different timing mark relative to the keyway. If the elastomer has allowed the outer ring to slip, get rid of that balancer. A new one starts at around $50 and a little labor is a lot less than a new motor. If it's just a mix up of balancer versus pointer, you may be able to get away with timing tape to relocate TDC on your balancer.
     
  4. Blue85

    Blue85 Troll Premium Member

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    Re: Here\'s one for the small block experts:

    Blazer1970, Wheels,

    Thanks, guys, great information.

    Do you know how close a sparkplug comes to touching the top of the piston? I don't know how hard (or expensive) it will be to find the device that Blazer1970 talks about for locating TDC. What I am thinking now is that I will get a sleeve with spark plug thread on the outside and smaller threads on the insde that I can thread a long bolt through into the combustion chamber. I can first get the engine to where I feel compression and then insert this contraption with the bolt threaded out so that it's about as long as a spark plug. Then I can thread it in until it first touches the top of the piston. Then I will turn the motor the other way until it hits the bolt agian. If the two marks are a long ways apart, I can thread the bolt in a little further and then start over. Does this sound like a good plan if I can't find (or don't want to pay) for the premade device?

    Thanks again.

    '85 JIMMY
    '90 paint/grill/trim 5"susp 33/12.5/16.5
    Fresh 350 B&M '87 TH700
     
  5. GMC4by4

    GMC4by4 Registered Member

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    Re: Here\'s one for the small block experts:

    Does your truck have a computer? Unless you ground the ALDL it MIGHT show advanced like that (depending on your computer and distributor setup). Just something to check.

    -Rick
     
  6. Re: Here\'s one for the small block experts:

    Hey I might be crazy but I dont think the ESS vehicles have
    a vacume advance.Mine is an 82 and it didnt have one it is ESS equiped.Hey on the timing just crank it up till it starts rattlen under a load and back it off just enough for it to stop,then you dont have to worry about none of the above!!!Thats how I do it!!LOL


    IF IT AINT BIG IT AINT BAD!!!!!!
     
  7. Blue85

    Blue85 Troll Premium Member

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    Re: Here\'s one for the small block experts:

    GMC4by4,
    No, there is no computer. I should have mentioned that already.

    Advance it till it you have knock and then back it off? I know that it could work, but I also know that it's not too fun for the motor. Actually, if I get the timing figured out, I'll probably do a curve kit or adjustable advance or something. Not that it doesn't work well, but I have this problem that I'm always trying to get things to work better :) Now if that money tree would only bloom...

    '85 JIMMY
    '90 paint/grill/trim 5"susp 33/12.5/16.5
    Fresh 350 B&M '87 TH700
     
  8. Re: Here\'s one for the small block experts:

    No dont wait for it to detonate that would be bad.Just a little valve rattle wont hert anything for a few moments.
    Put it in gear and hold the break and load the motor up like that.Dont take a trip across country to check it.LOL
    I know what you mean though,I would rather know than not know.But this will work untill you fix it,good luck.

    IF IT AINT BIG IT AINT BAD!!!!!!
     
  9. talldogg

    talldogg 1/2 ton status

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  10. Blazer1970

    Blazer1970 1/2 ton status

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    Re: Here\'s one for the small block experts:

    Anything that sticks through the spark plug hole and can be held in position so that it does not move when you switch motor rotation direction will work to find TDC. Jeg's lists the TDC locator tool for $11.69 (#778-66792). BTW Blue85, the tool is exactly like what you describe making in your post above.

    Tim

    1970 Blazer CST 4X4 350 SM465 NP205
    1987 Suburban 4X4 350
    1988 Chevy Pickup 4X4 350
     
  11. sosamantx

    sosamantx 1/2 ton status

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    Re: Here\'s one for the small block experts:

    If you think that you have a different balancer or balancer tab then maybe you can do this. I found an old article out of one of my hotrod magazines. I have done this to mark my balancers total advance, so that I have a reference.
    It says " an 8 inch balancer is 25.13 inches in circumference. Division by 360 degrees yields .0698 inch for every degree. For 36 degrees total advance, this would be 2.5 inches down for the TDC mark (.0698 x 36 = 2.51 inch)." Anyway you might be able to do something like this to make you a reference mark. However you will need to know aproximately how far the marks are different between the harmonic balancers. Ideally you would be better off just buying the correct harmonic balancer or tab for the application (one's that correspond). - Steve

    Steve Sosa a.k.a. "sosaman"
    http://sosaman.home.texas.net/carpics.html
     
  12. Blue85

    Blue85 Troll Premium Member

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    Re: Here\'s one for the small block experts:

    I've been letting this issue sleep for a while, but now I have more info. I pulled the oil pan off and got #1 to as close to TDC as I can. The timing mark on the damper is at least 35-40 degrees before the 0 mark on the timing tab. I will stick timing tape on it now to line up with the timing tab. I am worried because the rotor is pointing straight toward the front of the truck, or a little past. The books show that the distributor posts for cylinders 1 and 8 should be equally close to the radiator. Does this mean that my distributor was installed incorrectly? I'm sure I can work around that. (I have another post about my distributor being able to move a little...)

    It is a Goodwrench long block. Do these come with the timing chain pre-installed? I am wondering how many things could have been done wrong or "short-cutted" that I should investigate. I want everything to be right so maintainance and mods are easy in the future.
     
  13. dyeager535

    dyeager535 1 ton status Premium Member

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    Re: Here\'s one for the small block experts:

    what about taking a spark plug and knocking the center out of it?

    My dad made a spark plug into a fitting for an air compressor line, so you could change valves with the heads on the engine. (think thats what he was using it for) In any case, you could get the center out of a plug, and just find a bolt/rod thats a fairly tight fit, and use that.

    Don't use a thin blade screwdriver, if you aren't holding it, it gets cockeyed and stops the piston from moving ; )
     
  14. reddog64

    reddog64 1/2 ton status

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    Re: Here\'s one for the small block experts:

    the air tool is 6 bucks at napa...
     

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