I have an 86 Chevy G30 (ok - it's actually an old short bus) with a 350 in it. I've been using it for road trips and the 350 performs quite well, with the exception of getting about 7mpg. I'm currently doing all I can to reduce its weight and improve the aerodynamics some, but I have a good 305 out of an 86 camper van, and would like to know if swapping them out would give me a significant increase in mpg. I'm not too worried about speed or other issues, except possibly whether the bus might just be too heavy for it in the long run. Any help is greatly appreciated

 

What are the specs on the 305? I'm guessing throttle body injection right? The 350 most probabaly has more power (If only by slightly). The 305 doesn't way much less, and it has less power, so that means stomping on the pedle more to do the same amount of speed. Meaning worse fuel economy. I wouldn't go for it.

 

yeah, it's the TBI. So, probably the best I can do is hope to tune it up and modify everything else BUT the engine, huh? Well, I can drop those 16.5 wheels and some weight from the body...maybe an HHO system too ;p
Thanks for the reply

 

No problem. That's also a heavy vehicle man. Modding the enigne it has it in right now to have a little more power (to be able to compinsate for all the wieght), might not be a bad Idea. You have to mod it right though, or fuel econ will get worse. Best of luck to yah.

 

theres not very much diffrent between the two except the 45 cubic inch diffrence.sadly they get pretty much the same mileage .get some 16in wheels and michelin tires have much less rolling resistance.i would do headers and a free flowing exhaust.that will free up some more MPG .but you aint gonna get more than 15 MPG no matter what you do

 

7 MPG is pretty freakin bad. My quadrajet was getting 12 on the highway, but that was with the secondaries stuck open.

My first Camaro was a 1989 RS, and it too was getting bad mileage. We broke the carb down and gave it a good cleaning. I was averaging about 25 highway. My suggestion would be to look into the TBI unit before you switch the motor.

 

Keep the 350. The 305 will not be a happy camper (actually, it's probably not a happy camper in the van).

TBI is a good idea. Put that on the 350. Should get you up to 9 MPG. Put in synthetic lubes bumper-to-bumper, and you'll probably get up to 10.

Put in a 5.3, and you'll probably get up to 13-15.