Severe loss of power in my truck please help

i would like some help brainstorming whay may be going on with my truck. any help would me great. it runs a bit rough in park but has no power at all in gear.

it’s a 1986 c20 suburban with a 350

The first thing that you need to do is clue people in about the truck’s basic maintenance history. E.g. when is the last time it got new plugs & wires? Air filter? Fuel filter? There are many, many reasons for rough idle & lack of power. You need to help narrow it down.

sorry to cause any confusion. the oil was just changed. the plugs and wires were just done. the fireing order is correct. i checked the timing with my timing light. the intake vacuum is at 11 pounds. the mixture is set a 1 3/4 turns out. quadra jet carb. timing is at 6 deg btdc. i’m also at 5000 ft alt


When you step on the throttle, does the truck seem to ‘hold back’?

Perhaps the carb has a weak accelerator pump.

You may have dirty fuel filter or a weak fuel pump.

I’m not familiar with high altitudes for vehicles but at 5k ft it may need more air than fuel. In other words, run lean.

the intake vacuum is at 11 pounds

Does this refer to a reading from a vacuum gauge - 11 inches of mercury? (Those are done in in of mercury).

If that is 11 inches then I’d say to look for vacuum/intake leaks. 11 inches is too low even at 5,000 ft. I could be wrong about that. If you have a car that is running really well slap the gauge on it to see what you get. They should be similar if there are no leaks in the truck.

Air & fuel filters? I’d do those if they haven’t been and check the fuel pressure.

Well is it at least a steady 11 inHg?

Watch out for the #5 and #7 wires. Those are found swapped all the time. Did it run bad before the wires were changed? Pull all the plugs and see what they look like. Pull the distributor cap and see if the rotor is damaged and if the center electrode on the cap is intact. Look for frayed wires on your ignition pickup if you have one.

so far i have rebuilt the carb and that made it run a bit better but still no power. the vacuum does seem a bit low at 11inHG but it is holding pretty steady. i think that my next step is going to have to be an intake gasket. i pulled the distributor on the hunch that the timing chain might have skipped a tooth but the timing matches up. if i pull the vacuum line off the intake for the trani then my rpm’s go up and the engine smooths out quite a bit. any thoughts?

Your timing chain may be worn out and it may have slipped a few teeth.

so my timing chain was a bit loose but hadn’t skipped any teeth. i replaced it anyway. the only thing that i keep coming up with is a carburetor problem. i can’t seem to figure it though. i can close the mixture screws all the way and it stays running. now that shouldn’t happen. i’m at a loss and i don’t want to drop $500 on a carb if i don’t have to.