1986 Chevy Truck Lack Of Power When Under Load

LANHIGHLANDER

MEMBER
1986 CHEVROLET TRUCK

Engine Performance problem
1986 Chevy Truck 6 cyl Two Wheel Drive Automatic

1986 Chevy C/10, With a 1971 fresh rebuilt 250 cubic inch Inline 6. Ran for four months fine. Now has major lack of horsepower only when in gear. Idles fine in park, Revs nicely to the max and responsive. But in gear it wants to die, Back fires and lacks power. The usual suspects have been dealt with. A know good working single barrel carb installed, a know working distrubitor installed, new points, new condenser, new plug wires, new coil, new spark plugs, The push rods are dead straight. Fuel pump is good, Even the fuel has been checked for water or dirt. Still not working well. I am thinking electiral however mabye a bad valve or bad lifter, but the Head is new. Totally stumped on this one.

4 Replies

RASMATAZ

MECHANIC
75,992 POSTS

Check the PCV and EGR valves-also test the fuel pressure. Is the choke plate fully open when engine is fully warmed-up?

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Monday, January 5th, 2009 AT 4:02 PM

LANHIGHLANDER

MEMBER
3 POSTS

PCV valve fine, all lines checked for vaccum leak, No EGR pre-emissions. Choke fully open, not burning rich but does seem to put out to much clear smoke for an engine that is fully warmed up, Not steam. The fuel pressure is good, new fuel pump. Replaced all the fuel filters. I have a strong feeling towards a timing problem by the way it drives. But it is timed correctly, and the point gap is good.

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Monday, January 5th, 2009 AT 6:37 PM

RASMATAZ

MECHANIC
75,992 POSTS

Recheck the ignition timing-do you have a vacuum canister on the distributor if so disconnect the vac hose and plug it. Also check point gap or use a dwell meter and dwell it to 30deg-

You sure its not coming from a slipping transmission

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Monday, January 5th, 2009 AT 8:30 PM

LANHIGHLANDER

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3 POSTS

The transmission is 100%, It shifts hard with no delays. But I have realized something else, when put into gear when idling it is still fine and has it's torque. But when any acceleration is applied it wants to die, and back fires. This problem is keeping me up at night, all the usual suspects, carb, coil, distributor, plugs, wires, fuel pump and the fuel have been checked. I have been forced to take the engine out and tear it down, suspecting cam. The cam is slightly out of round by 0.005 in. The thrust plate is slightly damaged but nothing major. The cam bearings are worn but all uniformly, lifter are good and not collapsed. Still a mystery.

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Tuesday, January 6th, 2009 AT 6:09 PM