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New engine will not idle smoothly, and now won't stay running.

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by BigJim85, Aug 22, 2002.

  1. BigJim85

    BigJim85 1/2 ton status

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    New engine will not idle smoothly, and now won\'t stay running.

    I just put a new 350 into my 85 Jimmy. It ran pretty good, a little rough when I first started it up, but now I can't get it to even stay running. Last night I tried to start it and it would start, but the RPM's would just slowly drop until it died. We tried setting the timing today and it ran even worse where it is suposed to be set. Tried dicking with the fuel/air mixture screws but that didnt help. I got a stock Quadrajet, could it be screwed up? Or is my new engine hosed? I could also use the names of some good tune-up shops in the south-west Denver metro area in case I reach my wits end and give up.
     
  2. jimmyjack

    jimmyjack 1/2 ton status

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    Re: New engine will not idle smoothly, and now won\'t stay running.

    Was it rebuilt or a crate motor? There are ALOT of variables. Could be tight valves, vaccuun leaks, intake leaks....... blah blah blah. Start it up and spray carb cleaner around your intake and carb area and that will tell if you have air leaks. Good Luck!!
     
  3. mudhog

    mudhog THEGAME Staff Member Super Moderator

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    Re: New engine will not idle smoothly, and now won\'t stay running.

    check double check and triple check your plug wires sounds like you got 2 crossed
     
  4. Blazer_Boy

    Blazer_Boy 1/2 ton status

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    Re: New engine will not idle smoothly, and now won\'t stay running.

    (Skip to bottom paragraph to get to the chase)
    Bah, stock timing specs aren't good unless you have the stock vacuum routing. 12-16 intial timing with 20 degrees mechanical advance in by 3,000 rpm and 8-12 degrees vac advance on ported (vac line that doesn't have vacuum at idle). You can rig a stop for your vac advance or just buy an adjustable one.

    Valve setting is cake too. Have a buddy bump the motor and watch a partiuclar rocker arm. It should come and then come back down, give an extra bump after its down, and have at it. All you want to is to be able to spin the pushrod (should have some drag), but not have it move up and down. Then fire it up and fine tune it. Back of a rocker until it starts to tick. Then tighten it down until it just stops. One half turn past no tick should be set. This will be messy, so work fast, and have break cleaner on hand. Doing this on a fully warmed motor would be a big no no, unless you like burns and a higher oil fire risk. Otherwise, its no big deal.

    You may also have the firing order farked up. Remove the number one plug and stick your finger in the hole. Have a buddy bump the motor until you get a woosh out the hole. The set your rotor to the number #1 position BEFORE you drop the distributor in. (The more accurate way would be moving the timing marks by hand to inidicate 0 and have the distributor pointing in the #1 position AFTER its fully engaged. You can move the motor over by hand using a wrench on the snout of the crank. Be sure not to exceed 75 ft/lbs, as that is the torque setting for that front bolt). Drop it in the distributor hole. Then just keep bumping the motor over after you set it in until it enganges into the oil pump and falls in all the way. No need to keep pulling it out and moving the oil pump shaft with a screw driver like so many go on about. Kinda like people who insit on counting the teeth on the ring and pinion when the numbers are stamped on the ring gear /forums/images/icons/laugh.gif The order goes clockwise from number #1 (which is traditional placed by most in the bottom right corner)....1-8-4-3-6-5-7-2. Driver's side plug from front to back are 1-3-5-7 and passener 2-4-6-8.

    --My belief is that you have a mismatched crankshaft, timing chain cover, or damper, which is giving you an inaccurate timing mark. This is not anything to worry about, so don't think your motor is wrong. Over the years GM used 2 different timing mark orientations in the SBC. The older styles had the timing mark positioned 10 degrees before the keyway on the crankshaft. Meaning the damper and timing chain cover had marks dedicated to this system. The timing tab was located in the 2 o'clock position. Later models (like your '85) had the mark 2 degrees before the keyway and timing mark was in about the 12 o'clock position. TBI motors went back to the old style.
    So the crank, timing cover, or damper could be the culprit. Set the timing on your motor using a vacuum gauge. With the vac advance unplugged, advance the timing for best vacuum and retard 1". If that fixes it, then we'll have to go over how to establish a new TDC (which is very easy to do)
     
  5. BigJim85

    BigJim85 1/2 ton status

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    Re: New engine will not idle smoothly, and now won\'t stay running.

    Tried the carb cleaner trick, turns out I had one major vacuum leak on one whole side of my intake. EGR and my choke plate were leaking too. This has got to be the problem, I checked the wires - good, and the timeing mark is good. The carb still might be part of it, I had trouble with it before, but a rebuild seemed to take care of that problem.
     

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