Poor fuel mileage, BANG! Engine trouble!

[69GMC910]

Installed a performer plus cam in the 350, performer intake, and performer 600cfm carb also bolted on. Noticed a little power increase, and HIGH FUEL CONSUMPTION. The rest of the engine is stock and previously ran 20mpg using the 4.54 litres=1 Gallon.

So I put about 200-250 miles on the truck breaking the cam in. All is well at this point.

So today I went for a 250 mile road trip. I made it 87 of those miles and had to turn back home.

The engine started sounding rough and when I went to accelerate it would knock REALLY bad. Now I think I may have adjusted the pushrods incorrectly, is this would most of you would assume. I have done pushrods before and been successful, but I don't know about this time.

I had slack in them when they were off the cam lobe, I just hope i didn't have too much slack.

Would improperly adjusted pushrods cause poor fuel economy?

Help, I have to fix this in the morning!!!!


THANX!