I would say yer carb is prolly the problem. Maybe kit it or replace it. If they sit for a while it can gum them up. And with todays crappy gas who knows what it may have plugged or even eaten in the carb. If ya got good fuel pressure and ya think the pump is good than I would look to the carb. But it still could be a timing or ignition problem.

 

Make sure float(s) is free and working good in the carb, and the float(s) level is correct. Especially make sure the needle and seat(s) are moving freely and there's no debris in there, and it's letting fuel enter the carb. Check compression in a cylinder on each bank to verify that the timing chain hasn't jumped/stretched. (I realize the motor only has 20k on it, but some aftermarket chains can be cheap and prone to failure) Check fuel pressure by unhooking the fuel line off the carb and plug that line into a gauge, then pop off the coil wire and crank the motor for a few seconds. If all that checks out, hook up a timing light to the motor, start it up and check your timing at idle and up through 3000 rpm.

 

Looks like I am spending some time with the Bronco this weekend.

 

If I had to take a guess at it, I'd say the distributor isn't advancing the timing properly.

 

How can I tell if it's advancing properly?
In the past I have had a timing light on it while accelerating the motor and timing did chance.

 

Sometimes, from sitting, the advance mechanism will seize up. Stick a light on it and check it.

 

Take the Dizzy cap off. Pull the vacuum advance line from carb and suck on it. Watch the breaker plate. It should move freely this way.

 

OK I will check it out. Thanks!

 

would a bad cam or valve lifter adjustment cause my lack of power? It has adjustable roller rockers in it.

 

I would think it would run bad all the time then. Not just under a load