John808

Hey guys,

I just bought a 1991 Suburban a few weeks ago. It's my first car, hooray! It's got a few inches of lift, just dropped some 35s on it because the tires were bald all around, and we're set for the snow. I knew it wouldn't be all that quick, being how heavy she is and the fact that she seats 8 comfortably with a pretty underpowered motor. So I guess this is both a help request thread and an information dump.

The L05 motor came stock with about 190 horsepower and 300 lb.-ft. torque. It's got a lousy 8.3:1 compression ratio, but numbers have deviated between 8.1 and 8.8. Throttle-body injection is the equivalent of an electronic-carbueretor. Apparently the injectors themselves are good to 400 horsepower, but the throttle body intake manifold is only good to about 520CFM of air intake. Furthermore, the heads that came stock with the engine are swirl-port, severely limiting power and compression. The motor is fantastic at low-end torque, but as I mentioned, it is pretty underpowered for the ~5000 lb. vehicle it's trying to push.

I'm a college student and I couldn't pass up a damn cheap, well-running, relatively-low-mileage 4WD vehicle, especially for the snow; but at the same time, getting 14MPG highway // 11MPG city and staying pretty close to the city mark while driving through town (and this is before the new set of tires; old ones were 33") is kind of absurd on my budget. Especially because she has a 38-gallon tank.

I'm at that point where I feel that getting more power would actually benefit my gas mileage.

I've looked into head swaps (specifically Vortec heads), slightly more aggressive cams (which will probably require chip/ECM tuning), headers or long-tube exhaust, a carb swap, or even a supercharger.

Will update this post later, I gotta run to class.

Thanks for reading, guys!

73shark

Welcome to the forum.

One way to improve mpg would be to lose the lift and big-*** tires. The cheapest thing would probably be to get a spread-bore manifold and a Q-jet. I know a lot of folks pooh pooh the Q-jet but properly tuned, it's hard to beat.