1986 Chevy K10 - sucks for power :(

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one4fun

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Need some help/direction.

1986 K10 w/stock 350, 191K miles (not sure if motor was ever rebuilt), Quadrajet carb, stock intake manifold, 700r4 transmission, Thorley headers, 33/1250/15 BFG's. Not sure which axle's/gear ratio's it has. Truck just passed DEQ emissions testing on Saturday.

I bought the truck in June of this year. Had more power than it does now. I took it off road (in the sand) for the first time about a month after I bought it. After about 45 minutes of running in sand, it suddenly thought it was a Prius and would not even spin the tires in the sand and the engine would not rev up in gear. Drove it home and found I had two burn spark plug wires from resting on the header pipes. Replaced all 8 wires and plugs. Made a noticeable difference, but still seemed to lack power. Truck does not even spin the tires on dry pavement from a complete stop, (Running 33/1250/15) however it was able to before my run in the sand. I tow my 17' jet boat (trailered and fueled is about 2700 lbs). On open highway it does fine. Going up a moderate incline it seems to really bog down. Not uncommon for it to drop to 45 mph by the time I am at the top of a mile long incline. (This is after manually shifting it out of OD at 50-55 mph). If I press the accelerator to the floor, it has less power than if I were to slightly let off the pedal - just slightly up from the floor.

Checked the timing - still at 8* BTDC. Truck starts great. Idles good.

When in neutral and I press the accelerator to the floor and quickly let off, there is a pop-pop-pop from the exhaust. If I am accelerating with the pedal to the floor and then quickly let off, it will make the same pop-pop-pop from the exhaust.

Truck blows a small cloud of blue smoke when starting cold - immediately goes away - has done this since I bought it. Having the heads rebuilt is on the radar for the near future. Catalytic converter has less than 10K miles on it.

Gas mileage sucks. Getting 9-11 mpg. I was getting 13 mpg when I first bought it.

When running, I do not hear any hissing sounds indicating a vacuum leak.

I did put an OBD scanner on it and there were no trouble codes.

Not that it has anything to do with the motor's performance, but I figured I would throw this out there in case there is some electrical issue causing the lack of acceleration. The fuel gauge accurately shows the fuel level, but bounces around erratically regarless of which tank is selected - started doing this on the ride home from my off road adventure in the sand - the speakers cut in and out when I use the power lock on the drivers door, the drivers door window is SLOW to lower and raise and will not go all the way up or down when the engine is not running, the interior dome light seems dim. (bad ground? alternator? )

Soooooo, having said all that, I am asking for some assistance in where to start with diagnosing the problem(s) and in what order would make the most sense to do so.

I have the Chevy shop manual for the truck and the electrical/vacuum manuals and the tools to do the job. I am comfortable with DIY work on my vehicles as well.

Thank you.
Chris
 

Graystone

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Have you pulled your plugs to check them yet? It is going to tell you more of what is going on inside the motor
 

one4fun

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I have not pulled them since I changed them.

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Jims86

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If you have the stock 3.42s, then those 33s are part of the problem...stock tire diameter was 29".
That engine, new was rated at 165hp(155 in ca with the electronic q jet) and 285 ftlbs at 1800rpm.
Gearing is the key here.
 

gpmorgan

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I think I would check the alt. output and go from there on the elec. issues. Sounds like it may be time for some carb work on the bogging issue. Maybe a kit and good cleaning would fix it up.
One thing I forgot to mention here. You might experiment with the timing by bumping it up a couple of degrees to see if that helps with the power. Just don't advance it so much that the valves rattle.
 
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one4fun

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I think I would check the alt. output and go from there on the elec. issues. Sounds like it may be time for some carb work on the bogging issue. Maybe a kit and good cleaning would fix it up.
One thing I forgot to mention here. You might experiment with the timing by bumping it up a couple of degrees to see if that helps with the power. Just don't advance it so much that the valves rattle.

Alt: what is the normal output for these? Around 13.8v?

Carb: I will look into a carb kit and clean it up.

Timing: This is a buster on this truck. The timing mark is almost impossible to see or get a light on. I would like to set it at about 9-10° and see how it does, but I cannot even get in there to see the mark with a light. Any suggestions? :(

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Jims86

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Alt: what is the normal output for these? Around 13.8v?

Carb: I will look into a carb kit and clean it up.

Timing: This is a buster on this truck. The timing mark is almost impossible to see or get a light on. I would like to set it at about 9-10° and see how it does, but I cannot even get in there to see the mark with a light. Any suggestions? :(

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I have to shine the light behind the AC bracket, kind of a bitch, but you can do it. its hard not to cast shadows from the ps pump and the coolant pump.
do you have the electronic q jet?
 

one4fun

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I have to shine the light behind the AC bracket, kind of a bitch, but you can do it. its hard not to cast shadows from the ps pump and the coolant pump.
do you have the electronic q jet?

No kidding! That was the challenge I had. Well, I'll keep working at it.

Yep, electronic Q jet.

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MrMarty51

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When backing out of throttle and it seems to pick up on power indicates a plugged fuel system, either the fuel filter, the sock in the tank or the carb. is not allowing the fuel to flow through. could also be the adjustment on how soon the rear barrels begin to open too.
If after cleaning and checking everything else try putting a tad bit more tension on the rear barrel butterfly spring. That will make the rear barrels open just a bit later.
 

MrMarty51

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OH YEAH, You did`nt mention anything about the distributor cap or rotor, be sure to check the condition of those two components and clean or replace as necessary.
 

philjafo

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Sometimes its easy to overlook the obvious, you say you had it fourwheelin in sand. How's the air filter? With the timing thing I found it helps to mark the damper and the timing tab with a silver paint marker to make it easier to see.
 

GreaseDog

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If you have the stock 3.42s, then those 33s are part of the problem...stock tire diameter was 29".
That engine, new was rated at 165hp(155 in ca with the electronic q jet) and 285 ftlbs at 1800rpm.
Gearing is the key here.
3.42s would be a best case scenario... Most of them got 2.73 or 3.08 gears.
 

gpmorgan

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Alt: what is the normal output for these? Around 13.8v?

Carb: I will look into a carb kit and clean it up.

Timing: This is a buster on this truck. The timing mark is almost impossible to see or get a light on. I would like to set it at about 9-10° and see how it does, but I cannot even get in there to see the mark with a light. Any suggestions? :(

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Usually around 14 to 14.5 volts on the alt output.
As mentioned, you'll be able to see the timing mark on the balancer a little better if you take a marker and paint the timing line.
 

MrMarty51

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Use one of those "White out" in a bottle things to shine up the timing marks, thats what I use, works real good.
Turn the balancer until You can get to the mark then paint away.
 

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Sometimes its easy to overlook the obvious, you say you had it fourwheelin in sand. How's the air filter? With the timing thing I found it helps to mark the damper and the timing tab with a silver paint marker to make it easier to see.

Lol, mines red cause thats the 1st bottle of model paint i found.
 

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