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-----Engine Timing----- General Questions, please help!

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by dawson444, May 8, 2002.

  1. dawson444

    dawson444 1/2 ton status

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    I have an 88K5 w/ a 350HO (330hp) GM engine, I need to adjust the timing on it I think, it doesn't idle very well at all and stalls at stop lights a lot. Can someone walk me through what I need to do. Thanks!
     
  2. Blazer_Boy

    Blazer_Boy 1/2 ton status

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    Well is the carb and choke known to be good? Try on something else to be sure. You probably have something like waaaaay to much vacuum advance or the opposite, very little initial timing. That motor is supposed to be timed at 10 degrees BTDC, but try telling mine that. I built a copy with stock style flat-tops and 4x4 extreme cam (.447/.462 210/218 111 seperation angle) and it wants 14 degrees, otherwise it knocks when I try starting it warm. First, lets get you some good equipment. Go buy a crane adjustable vacuum advance kit. It has springs, and an adjustable advance can. Personally I use accel/mr. gasket kit because you get weights and bushings. You have to buy the adjustable advance can seperate.

    First, lets determine if you have ported or full vacuum. I prefer ported for something like you're running. This way your vacuum advance won't kick in until you're cruising. Vacuum advance should contribute little to performance. It will help some light throttle feel and fuel economy, but the meat is your mechanical advance. Get your Blazer warmed up and plug off the vacuum advance. Run your initial timing as fast as you can until it kicks when starting, then back it up two degrees. Then put in your springs, or weight/spring kit and have at it. Try the medium weight springs and go out and run it hard. Like a spot on the highway where you can turn around easy at. Listening for pinging. If you hear it, then put in a heavier spring, if not go lighter. Once that is kosher, hook up your vac advance. You basically also want to run as much as possible with out pinging. Start low and keeping adding until you hear it, then back off a turn or two.

    Try your initial anywhere around from 10-14 degrees.
     
  3. GMMANIAC

    GMMANIAC Registered Member

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    You didn't mention if your using the factory TBI, or a carb, or if you changed out the distributor to one with a vac. advance.
     
  4. Blazer_Boy

    Blazer_Boy 1/2 ton status

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    D'oh! Good point. If its TBI, here's what you do. Look around by your brake booster and fuse block for a big bundle of wire in a black tube. There should be one little wire outside of it that has a brown wire with a white stripe, unplug it. Start the truck and set your timing to 0 degrees. Turn the truck off, plug the wire in and disconnect the battery to clear the computer and then hook it back up. If it still is running funny, like when its warmed up, then change your temp sensor. Its the one on top the intake by the water neck.
     
  5. Blazer_Boy

    Blazer_Boy 1/2 ton status

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    Couple revisions for you here. Go to full vacuum on the advance. It will be more responsive off idle. If you still have the TBI setup then that wire a tan wire with a black stripe.
     

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