The difference between 305 and 350

[67_C-30]

Originally Posted by special-K

The right cam makes all the difference in the world and will dispell all myths that a 305 or 307 can move a truck well enough to gain mileage.I overhauled what my`71 K/20 had in it one time.With an RV cam,450 cfm spread bore,headres/duals,HEI,and 1.94 heads in a 4.57 geared 14.50/37 tired utility bed equipped work truck that weighed a good 7,000# I got 13+ mpg avg mileage and hauled that load like any 350 would on more fuel.
I hear of better mileage out of 305s than I`d ever expect to hear from a 350.

Are you talking about a 305 or a 307. Two totally different engines. I've had many 305's and I was never impressed by the fuel mileage on any of them except one I had in an '89 RS Camaro. I got 24 - 25 MPG on the highway, but my buddie's '91 Z28 with a L98 TPI 350 gets better mileage than my RS did, so there again I can't the 305 was any better. I get 11 and 12 out the 383 in my car hauler which has a Xtreme 4X4 cam, 600 Holley and Aerohead 76cc heads with 1.94"/1.50" valves. It has a SM465 with 4.10's and 235/75/16 tires which measure around 31". My truck weighs 8800# without me in it, so its rolling over 9000# down the road. I promise you there isn't a 305 alive that will outpull this puppy! I have a broken Eaton HO72 rearend, a Dana 70 yoke and 2 driveshafts with the ears broken off that will stand by that statement! I pull junkers out of fiels and woods sometimes that are full of rocks, logs and ruts. I have to be real careful in first gear because if the truck ever bumps around hard enough to make me stab the throttle just a little bit, it will break stuff if it doesn't spin the tires.