350 - no power

Discussion in 'Chevy C/K Truck Forum' started by meborder, Feb 15, 2014.

  1. meborder

    meborder New Member

    Maybe i'm expecting too much from a 350 ... but my truck just seems to not have any power.

    it rarely leaves the property, as it is mostly just a yard truck, but driving it to the gas station yesterday, it wouldn't even hold 65 MPH without kicking it out of overdrive.

    it's an 83 K20 with a 350 and 700r4. Gearing is unknown, and the stickers in the glove box are gone, so i can't even look it up. just judging by the sound of the engine while driving down the road, i'm guessing it is 3.73's or 4.10's, but i really don't know -- no tachometer either.

    i wasn't pulling anything, but i do have a plow on the front and 1000 lbs of ballast in the bed.

    it has the stock intake and carburetor, but i do have headers and full length 2.25" mandrel bent true dual exhaust (flowtech headers and exhaust, FWIW).

    my ignition timing is another unknown. the indicator is missing, and it appears that the damper has slipped, so i just set the timing by feel. I snuck it up until it was having hard starts when warm, then backed it down a bit until it started better.

    wondering if the mechanical advance is not working ....

    I'm kind of a ford guy, and this is the only 350 powered anything i've ever driven. But i'm just surprised by the lack of power on the road. it runs REALLY good, and seems to have good low end power when pushing snow, or moving heavy trailers around the yard, but on the road it is really doggy ....

    any ideas?

    my spring time plan is to get a new damper and timing indicator and start there, but i'm wondering if a $90 distributor from Summit might be a worthwhile purchase..

    any thoughts?

    i don't hang out here much, but look forward to hearing back!

  2. Scott_Anderson

    Scott_Anderson Rockstar 100 Posts

    I think you are on the right track to replace the damper and timing marker and start from there. Timing has a big effect on the power curve. Vac and mechanical advance both should be able to be checked once you have a timing reference.
    Also check for any vacuum leaks, old hoses, vac brake booster and such.
    How's the transmission fluid.
    Have you tried to drive it without OD? Sounds like you have quite a bit of weight to the vehicle for OD.
  3. Dana W

    Dana W Rockstar 3 Years 500 Posts

    a 350 only has about 260 hp. Unless it's geared pretty low, 1,000 lbs of ballast and a plow is not going to make it feel like a A/A fueler. But, it should be able to hold it's own, even up hill. It very well could be a dried up oxidized advance mechanism but I think by 83, this was computerized and should be throwing a code or two.
  4. meborder

    meborder New Member

    Thanks for the replies!

    The transmission is tip-top. I did do a filter change this fall and 4 qts of new fluid, but the fluid that was in there looked pretty good. it shifts firm and holds gears like it should.

    There are no signs of vacuum leaks, and the break booster holds vacuum for weeks. The vacuum advance on the distributor is working, as the idle goes way down when unplugged (running manifold vacuum, which i prefer -- i know that's a hugely debated topic).

    I don't think anything on this truck is computer controlled, but i could be wrong. It looks to be just the standard HEI ignition. how would i tell if it is computer controlled?

    I have done a tune up on it also. new plugs and wires, and i checked the cap and rotor but they looked like new so i didn't replace them.

    I guess i wasn't expecting NASCAR truck series type performance, but it won't pull any hill in OD, and with any kind of load in the bed it won't even pull from 60 to 65 without downshifting.

    the best information i can find rates a 1983 k20 w/350 at 160hp @3800 and 250ft-lb @2800. which is pretty weak. Makes me think that i'm probably just expecting too much. on the bright side, with the headers and thrush chambered mufflers, it makes all the happy V8 sounds when you mash the loud pedal :) (which i do, often :))

    just wondering if they are all like this....
  5. Scott_Anderson

    Scott_Anderson Rockstar 100 Posts

    If you are wanting to get more power from it, after you have the timing adjusted and set, you could look for some intake/carb improvements. If you happen to still be 2brl you could look at changing it to a 4brl.
  6. meborder

    meborder New Member

    To be honest, it is more an exercise in proper diagnosis.

    I do like to have my stuff run as good as it can, but for what I do with it, it runs plenty good. It is just the stunning lack of power going down the road leads me to think that something is amiss. More power is always good (i'm a car guy, afterall) but that's really not the point.

    it has the stock quadrajet carb and intake, and the headers and exhaust were installed to solve a different problem (http://www.gmtruckclub.com/forum/showthread.php/90547-83-K20-Still-earning-its-keep)

    I would like to see if i can make it better, but it might be a while before i get to it as it is not a huge priority. last year the truck got 300 miles on it, most of which were idling around the yard moving snow or backing trailers. the only time it leaves the yard is to get gas or help a neighbor move snow.

    thanks for all the replies!

    still open to any ideas.

Share This Page

Newest Gallery Photos