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Hi-Po motor timing woes

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by Blazer_Boy, Apr 7, 2002.

  1. Blazer_Boy

    Blazer_Boy 1/2 ton status

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    (Skip to second paragraph if you don't wanna read my rambling)

    I'm having trouble trying to find a timing setup for my motor. I had a problem with a wrong balancer in a previous post but have since changed the balancer. TDC is now in the correct spot. The motor is a '74 4-bolt main with stock flat-top pistons, L-31 vortec heads (aprx compression of 9.5:1), and Edelbrock performer intake with a 12-235 comp cam (.447/.462 210 218 @ .050 and 111 centerline and cam is pre-advanced at 4 degrees.) The exhaust are a GM stainless tubular manifolds with 2 1/4" duals with glasspacks.

    The distributor setup that I started off with was a 20 degree vac can with Mr. Gasket advance kit (used light spring and medium spring). I fired the motor up the vac advance line plugged shut and proceeded to time up. Got it 8 degrees before and plugged the vac advance in, then it stumbled and stalled out unless I got on the throttle. I took as far back as 10 degrees and still the same deal. It would run with the line loose, so a vac leak wouldn't explain it. I popped off the cap and put in a 15 degree can I had laying around and it will stay running with it plugged in. I had it running 10 degrees before and had plenty of guts, but kicked a little after trying to start it warm.

    WHAT IN THE HELL SHOULD I USE?! Should I get even less vac advance? Spring setup OK? Also very interested in knowing how to tell when its pinging. Is it a violent jerk similar to a fuel problem or does it feel different.

    Thanks
     
  2. Blazer_Boy

    Blazer_Boy 1/2 ton status

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    OK, I need some opnions because I'm making an a$$ of myself here because I'm just shoting in the dark. I got the correct balancer now, I need to buy a bolt on tab to get the right alignment. I was running was fast timing. The reason it was stumbling was because I had it plugged into manifold vacuum instead of porting. So when I was gunning it and need extra advance for more power, I was actually loosing my advance.

    I've been trying to set my mechanical advance. I lost one of the springs from kit and it really ticks me off! I plugged vacuum advance and drove it. When I get after it goes like no other, then has a slight bog and starts to pick up after that certain RPM band. I have one light spring and one medium spring in their now. I don't have much vac advance to run either. If I have it plugged in and drop the hammer in third, there's no response. I currently have a 15 degree can installed. I was considering buying an ajustable can, but can't bring myself to shell out $20 when I have a 15 18 and 20 degree can to choose from.
     

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