Hi Guys,
I have wandered through the board and haven't found any more ideas on how to deal with this. I have a stock 84. I haven't owned it very long and the previous owner didn't run it much if at all. Everything seems ok at first. Pretty good acceleration from a standing stop. Runs up to 55 fine. Then after a mile or more it loses power and can barely hold 50. If I come to a complete stop and wait a moment, I can feel something switch and the power is back... zoom back on the road. I have already changed out the plugs, fuel filter and air filter just on general principle. Any good ideas?
Thanks.

 

Maybe catalytic converter is clogged.

Might be fuel pump not putting out enough volume or fuel system might be contaminated with rust.

 

Check for crap in the tank or a for a plug return gas line from the carburator.

If theres loose rust or flakes of stuff in th tank it will clog the pickup as it sucks up the gas. Try bouncing the car and listen for hard stuff sloshing in the tank. Does it do it more when its near empty? Sometimes thats a clue as well.

 

The shutter valve could be kicking in when you get to 55 and stop accelerating, it kills the power to the rear rotor when that happens. Block it off and see if that takes care of it. That would explain why the power returns and you hear something click back over at idle.

 

i recently had the same thinghappen on a turbo webber setup. new fuel pump solved all.

do you have a pressure gauge on your fuel line by chance?