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Discussion in 'The Garage' started by GA84K5, Mar 11, 2007.

  1. GA84K5

    GA84K5 Registered Member

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    OK...I've lurked a bit so now I'm asking.. Had my K5 about 5 months....a work in progress...84 model, 305V8, Auto, NP208, stock axles. Just can't seem to get it running well. Hate to put it in the shop. Here is what I've done: full Tune Up ( plugs, wires, cap, rotor, ingition module), fresh rebuilt carb, thermostat, magnaflow cat, heater hoses, many vacum lines replaced. Just doesn't want to "run right". Sounds like crap (could be the crappy muffler po installed). Very rough idle. Timing looks about right. Damn I hate where the timing marks are ( can these be moved down with a Jegs or Summit SBC timing mark add on?). Suggestions. Thanks in advance.
     
  2. K5dreamer

    K5dreamer 1/2 ton status

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    well, one thing you might try is a compression test. make sure youre trying to make a solid engine run well as opposed to flogging a dying horse.

    check your sparkplug gap, check for vacume leaks, recheck your settings on the carb, if youre rebuilding a really old engine with alot of miles, youre timing chain may also be stretched, meaning that if you line up the timing mark, you actually will have the cam retarded a bit. i would ditch the timing light and set the engine by vacum.
     
  3. GA84K5

    GA84K5 Registered Member

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    I had contemplated the compression test. What should I bet getting with a 305 ( with many miles I should add )?

    I've never set the timing via vacuum. It this via a vac gauge off manifold vac or are we just timimg by trial and error?
     
  4. ryan22re

    ryan22re 1/2 ton status

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    The numbers should be even. Maybe 10-15% variation between cylinders. I would say around 120-150 psi should be ok.

    Yeah, set the timing to get the highest manifold vacuum reading. Then adjust the idle screws (speed-if you have a tach and mixture) to get the highest manifold vacuum reading. Then go back to the timing. then back to the carb.

    What kind of carb are you running?
     
  5. tRustyK5

    tRustyK5 Big meanie Staff Member Super Moderator GMOTM Winner Author

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    I've always set timing by ear and had the best results that way. I keep advancing it a little at a time until I get light pinging under very light throttle...then back it off a little.

    I've also found the mechanical advance gums up easily and stops working as it should on a few rides I've had.

    ~110-120 psi should be a good range for your engine...but more important is that all 8 are within 10% of each other.

    Rene
     
  6. GA84K5

    GA84K5 Registered Member

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    OK...the carb is a fresh rebuilt Q-Jet from Mountain Man Fuel Systems over in Ark....got an email over to my brother to borrow his compression tester ( might just order myself one from Jegs since they are only like $30 )....

    BUT I completely forgot to admit my one screw up and my other thought....

    the screw up....during the installation of the carb I got a (newly replaced clear slicone ) vacum line caught between the carb and the gasket and now I'm thinking I crushed the gasket and that could be a leak....

    the thought was the crappy EGR valve...it looks like total sheout and maybe it's not even working....my other desire is to start eliminating this rats nest of vacuum lines on this thing....my worry is the couple of vacuum lines that have electric hook ups and what they do... in going over the sticker on the grill header panel 70% look right but the other 30% just don't.
     
  7. ryan22re

    ryan22re 1/2 ton status

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    Fixing any vacuum leaks and properly routing the vacuum lines would be the first step.

    Unless there is a manifold vacuum leak at the valve or the egr valve is stuck open, I see no need to replace it in this situation. Properly working, the egr valve should make the engine stumble when fingered. (i just like saying that)

    Is the replacement carb computer controlled?

    If the computer controlls have been eliminated, is the dist. still running (or trying to run) off of the computer?
     
  8. GA84K5

    GA84K5 Registered Member

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    The vacuum lines I agree must all be worked out.

    The EGR valve really just looks like total crap and I've had other vehicles that once all gunked up gave all types of drivability problems. I was however extremely surprised at how clean the intake looked when I swapped the carb.
    Not really sure if I can get my finger to the EGR but maybe worth a try ( why does that make me chuckle to respond to )

    Regarding the carb. It previously WAS computer controlled. Meaning it had the blue ( or was it tan ) connection at the from of the carb/engine BUT nothing was connected to it and I could not figure out what on the truck it SHOULD have been plugged into. After speaking with my carb rebuilder several times he indicated that he could build my carb either way. He could not tell me what underhood wires it used. So the replacement doesn't have this hookup which I understand was for a fuel slenoid that many people run disconnected.

    More history, I had three wires not connected. One I am using for the choke now since it was 12V with the key on (can't remember the color). One that is pink(ish) and I couldn't figure out what it could been attached to. It previously had the almost double plastic blade plug attached but was melted so badly I cut off the end taped it up and have it coiled up and fastened to the firewall. It had no voltage to it with the key on. There was also a three connnector almost water proof looking plug at the firewall that I still have no idea what it should be connected to.



    OK...and the craziest part of the history( not really but it's wierd enough ).
    I bought this thing via eBay (a great $1,200 buy ). Drove 6 hours to get it ( I'm outside of Atlanta it was all the way past Rockingham, NC ) and then filled it up with gas and drove it home. I feel I've somewhat made it drive worse since replacing so much stuff but looking at what I've replaced some would say "How was it running before????"

    It's frustrating but that's the fun part right? ( Please just say yes)
     
  9. ryan22re

    ryan22re 1/2 ton status

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    I think if you search around here for ( I couldn't find it) or maybe fullsize chevy you can find a way to make your computer controlled dist. work like a normal HEI. I did it to mine. Wasn't having any problems before I did it either. I though I had the picture saved on how to do it, but I can't find it. All you had to do was jumper two of the four wires coming out of the dist. together.

    The three wire connector on the firewall is most likely the map sensor connector. It measured manifold vacuum. Not needed now.

    Back in the day, when the computer controlled carbs gave us trouble, the first thing we would try is unplugging the mixture control solenoid. Then remove the idle mixture screw plugs and adjust them.

    It's fun and frustrating all at the same time. It's also a very good learing experience. Good luck.
     
  10. GA84K5

    GA84K5 Registered Member

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    I've found this previously....

    "FWIW, the only thing that's been changed was, I jumpered the 1st and
    3rd pins of the 5-pin module together to bypass the ESC (cheapo
    ECM-like device that retards spark based on input from a knock sensor).
    This mod was/is GM approved and was released in a service bulletin
    years ago."

    My only issue ( since I just had some of this fun last weekend ) is that my
    distr. only has 4 connections. One large and One small blade connector towards the firewall and One twin connector towards the front of the engine. So I'm thinking that mod is not for my current configuration. ( I actually had to make the dual run back to the parts store because they gave me the 5 connector module the first time AND they didn't even list a 4 connector module but amazingly the guy behind the counter knew which one I needed..I was shocked. )
     

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