<VV> Power problem GM - Not Corvair

[Craig Nicol]

I had a similar problem with my GMC motorhome. After many false leads, I
finally found that the metering rods in the Quadrajet were stuck in the down
position. A carburetor rebuild fixed it. I thought I had a fuel delivery
problem but then I noticed that if I floored the accelerator and opened the
secondaries, it would go; obviously not a pump/filter problem.  The cat is a
good possibility too (if you have one). Normally, a mechanic checks the back
pressure at 2500 rpm using a gauge installed where the O2 sensor goes. Since
you don't have an O2 sensor, you have to use a vacuum gauge.  Look for a
steady drop in vacuum with the engine held at a constant 2500-3000 rpm -
indicating increasing backpressure from a plugged cat.

Craig Nicol