I've had a '78 F150 (351) for about 6 months now. It's been running great. I put it in the garage a couple of days ago to work on the brakes, and now it's idleing really rough, stalling, "bucking" and tonight, the muffler got cherry-red hot and glowing. I can't figure out what would have happened so quickly. It's got a new carb, plugs, wires, distributer cap. Any ideas? I'm really frustrated. Thanks!

 

check your exhaust pipe for a potato (just kidding) nothing else comes to mind right now.

 

How many miles on the engine and has the timing chain ever been replaced?

Check and see if the ignition timing is way off, if it is the timing chain may have jumped a tooth.

 

Is there a plugged Catalytic convertor on that truck ?

Place you hand over the exhaust pipe opening to feel how much
is coming out.

The have someone rev it up while your hand is still there.

 

My guess goes with Torque1st.... To get my clunkers through emmissions I used to retard the timing as far as possible and still run ...That causes fire to excape the cylinders before the gas is completely burned... The result is fire and heat all the way back through the exhaust, making a longer burn, eliminating pollutants..... At least thats the therory I have why it worked...