i was wondering if a 1986 302 roller cam (out of a car) engine would get better gas mielage that a non-roller cam engine, both being carbed with stock
2 barrel?

 

Good question, but I would think that the answer would be tough..... one of those, "It depends" type. In theory, I would think the roller cam would result in less valvetrain friction, translating into more horsepower, which would likely translate into better gas mileage. By all rites, this should be the case..... in a car. In a truck, I'm not really sure this would be the case or, at least not to the point where you would see much of a difference. The reasoning would be in the cam profile..... if the roller cam was ground for low-end mid-range torque, you'd likely see a mileage improvement, as this is favorable for getting heavy trucks up and moving. If, however, it was ground for higher-end torque and horsepower, which might well be the case if the cam is out of a Mustang or other car engine, I'm not really sure you'd see the same benefits when installing it in a truck. If your powerband were at a higher rpm, and you were finding the need to run the engine up more to realize the extra power and torque, I'm not really sure that you would realize any increase in gas mileage, even given the reduced friction. Do you know what specs (duration and lift) the roller cam would have?