HELP! Need gas mileage!
Question:
Hi I have a 1975 GMC Sierra grande P/U with a 350 small block and it is getting so expensive that I almost can’t drive it, The price of gas is skyrocketing up here in Canada at an alarming rate! I love my truck and I want to keep it, I have a turbo 400 tranny with a four barrel quadrajet I would like to know how the mileage is on the same engine but with a 2 barrel carb or a different tranny. Thanks ahead from a freindly Canadian: Mike
Response:
The two barrel will help around town, but not by much. I assume the four barrel works properly, some leak internally, and waste fuel. How do the plugs look ? Black soot = too much fuel [ leak ] The killer setup would be a fuel injection setup. The TBI bolts on prettymuch, conversion kits are available. Going to a smaller engine is bogus, the engine works too hard. A bad torque converter can suck up the gas too.
Response:
Want to improve mileage and increase horsepower and not spend a fortune? Look at the fuel flow of the motor. What does the hardest work? The heads!!!! Take off the heads and not only have a valve job with new seals, cut the heads!!!! That’s right, shave the heads enough to bring up the compression ratio to around 9.5 to 10.0:1. The end result is not just more horsepower, but better fuel economy. The motor needs to do less work to go faster and it uses less fuel to do such. My old 350 in my Monte Carlo SS(it came with a 305 but I replaced it after it blew, I was the 2nd owner), not only went from 230 hp to 265, but I also gained around 5-7mpg. I brought the factory compression ratio from 9.0:1 to 9.75:1. You can go as high as 10.5:1 with steel heads and run pump gas without a problem, (did that to my 84 Vette motor). You can go as high as 11.0:1 with aluminum heads and run pump gas. On my Monte Carlo SS, I spent a total of $235. I did the labor though. That included the head gasket set and the head work at a good machine shop. Keep in mind though, if you cut too much off the heads, you may also need to face match the intake manifold. That usually runs around an extra $50. These are also prices in Miami,Fla. I know the prices for these things would be much higher when I was in Wisconsin. — Thomas (Tom) Smalley Hi I have a 1975 GMC Sierra grande P/U with a 350 small block and it is getting so expensive that I almost can’t drive it, The price of gas is skyrocketing up here in Canada at an alarming rate! I love my truck and I want to keep it, I have a turbo 400 tranny with a four barrel quadrajet I would like to know how the mileage is on the same engine but with a 2 barrel carb or a different tranny. Thanks ahead from a freindly Canadian: Mike
Response:
> Hi I have a 1975 GMC Sierra grande P/U with a 350 small block and it is > getting so expensive that I almost can’t drive it, The price of gas is > skyrocketing up here in Canada at an alarming rate! I love my truck and I > want to keep it, I have a turbo 400 tranny with a four barrel quadrajet I > would like to know how the mileage is on the same engine but with a 2 barrel > carb or a different tranny. Thanks ahead from a freindly Canadian: Mike
The 2 barrel won’t help you out in mileage, unless you keep the petal mashed lots on the 4 barrel. The Turbo 400 sucks back a little more HP (I think!) than a Turbo 350, but not enough to warrant changing it. If you twin the exhaust (if it isn’t already done) and install low restriction mufflers (Like the Dynomax ones), you can gain 2 MPG easy. — Lyle Pakula
