Quote:
Originally Posted by James McClure
Gentelmen. This may be a case where more=less. I have an 84 K20 with a 350M engine fed by a quadrajet carb and rear axel ratio of 3.08. Trans is a 4 speed "rock crusher" Tires are 235-85R 16. Most of the time vehicle is empty (7100 LBS) but I do pull a 8 X 16 utility trailer sometimes. I admit I am a light footed driver and run 60 to 65 on the interstate. When I'm empty I get between 17 & 18 MPG. When I pull the trailer (7000 LBS GVW) my mileage drops 13 to 14 MPG. Total combination weight loaded is 15,600 LBS. The 305 doesen't have much torque so it's working harder and using more fuel as a result. One has only to look at a semi to see what torque can do. 80,000 LBS and around 10 mpg.
Don't push it so hard. Like d13 says. Also take into account the terain. Hills, even little ones will kill ya. Is the TCC working correctly? If the CE light doesen't come on the engine is working correctly as are all the related systems. jim
|
Jim is getting there. You need more torque in the usable rpm range you normally drive in. You need the throttle open much farther with the 305 than you would with a 350 or 383, because they are making more torque. You want to increase torque and you can do that with the 305, but it will take a bit of effort and some new parts.
A quick and effective way to bump the grunt of a 305 is a head and cam swap. A set of Vortec heads drilled so you can use your stock manifold, and a cam that makes its power from idle to 4500/5000 rpm. A cam like the Comp XE264, nothing radical but capable of getting the grunt out of your tiny engine.
The engines in the 80s werent set up for mileage nor power, they were set up for emissions and everything was compromised and crutched to make them pass. You can improve the efficiency and torque of your engine and have it burn cleaner with the right selection of parts. The 87 454 in my swb gets 8-10mpg because it is neutered from the factory. All it really needs is an intake, cam, and valve spring swap. It should have no problem pulling my car trailer, with my roadbox and tools in the bed, and the car on it once its done.
If I can get 22-25mpg from a 450hp/500ftlb 455 in a 4200lb 70 GTO, with a Qjet and 2004R trans, you should be able to get 18 with the 305 if you get it to grunt. The GTO would loaf along the interstate at 1700rpm, wouldnt need to downshift up any hill or to pass, it ran on 87 octane and had 2.93 gears with 28" tires. make the grunt in the RPM range you drive in and you will get better mileage. FYI the aero on a 70 GTO isnt much better than my swb, and with that setup it would run 13.50s @105mph all day long.
With a truck you want torque, hp is nice but does little for you.