Oldsmobile/Buick Repair: Engine looses power at 55mph, grand nat, fuel test

Question
Howdy, I have a 1987 grand nat. The engine runs good with power and acceleration up to 55-60 mph and then looses power and bogs down. I can stamp on gas but it just dosen't accelerate. I let the car cost and let it get down to about 40 and the engine seems to respond and I can accelerate only back to 55 or so. We looked at what we think is everything. What about timing?
we are running a edelbrock 500. Metering rods?
distributer? This has a few of us going nuts. Any suggestions? Dave

Answer
Hi Dave,
On your fuel test....if there is plenty of gas there, might advance the timing a little.

If that carb has the little filter in it where the gas line connects, and it is the paper filter with the rubber check valve, make sure it isn't in backwards.

Van