305 gas mileage?

[cstiles]

Have a  81 custom deluxe short bed 2x4. With a low mileage 305 and a edelbrock 500 .turbo 350 behind it and the gears ain't to bad.I'm turning 2100 rpm at 60 mph. I'm getting avg 11 miles to the gallon. I do need to tune the carb like the  jets, rods etc.but shouldn't it get better than that or am I expecting to much out of the old girl.it also has a e fan and dual exhaust with headers.I guess I'm really just trying to see what everybody's fuel mileage is with similar set ups.

[VileZambonie]

A 700R4 will help, what's your final drive ratio?

Have you optimized the timing? Standard vacuum advance HEI? After you dial it in you need to adjust your carburetor, it's probably over-fueling if it's straight out of the box.

[cstiles]

It is untouched besides the screws on the carb.gonna try to get a wideband air fuel gauge. Unsure of the final drive .just wondering what I should expect out of it.11 is craps for a 305 I would thank .standard he I . I have not really done much to it

[Irish_Alley]

its been too long but i think my 350 wih a th350 in my 86 was getting 10 -12. it was my first truck that had a carb so im sure nothing was tuned right. but even a tbi 350 with a 700r4 are only seeing 16-18

[zieg85]

A dialed in 305 should get 14-15.  I actually got 16 out of my 85 with the TH350C with 2nd gear out of it.  Timing is a big MPG draw if not right.  I had a regular distributor in mine and total advanced timing was 32.  Gearing/driving habits/tire size all come into play.  305's are slugs if not just right

[cstiles]

Mines not a slug just likes gas.if I could get 15 whwn I got all the work don'e.that'd be great

[Stewart G Griffin]

What's your axle ratio is a big key here.

i was able to get 17.56 once, but that was all highway.  average is about 16.   And this was a 78 LG3 305 out of a 78 malibu.  "Just" a rochester 2g carb and HEI ignition.  i rarely exceeded 65mph, although it was certainly capable of doing 75+.

See my thread entitled "mpg pt.1"     i think the tonneau cover can help.


Going slightly off topic one thing i'm, curious about is if you took the latest intake off of an LS engine, which is i think basically a tunnel ram and multiport injection?  And the distributorless ignition.   And adapted both those to a gen 1 smallblock with vortec heads and roller lifters, how much better mpg would the LS get if any?

[Stewart G Griffin]

Actually, first tell us how you are calculating your mpg?

[cstiles]

Fill her up drive it till needs more gas. fill her up again take miles driven and divide by gallons of gas used

[Irish_Alley]

Fill her up drive it till needs more gas. fill her up again take miles driven and divide by gallons of gas used

i would verify this via gps on the phone if you havnt. i have a app on my phone for a speedometer it will tell you your miles accurately

[Stewart G Griffin]

Fill her up drive it till needs more gas. fill her up again take miles driven and divide by gallons of gas used

Ok, good.

Do you know what your axle ratio is?

[big_al273]

I couldn't say for certain as i have no personal experience with anything but my truck for mileage, but my TBI 454 is getting 9.75 MPG religiously and from my dads input (he has owned and driven at least two squares that i know of) 15 MPG should be around average for a 305/350 half-ton truck driven reasonably (no lead footing it)

Going slightly off topic one thing i'm, curious about is if you took the latest intake off of an LS engine, which is i think basically a tunnel ram and multiport injection?  And the distributorless ignition.   And adapted both those to a gen 1 smallblock with vortec heads and roller lifters, how much better mpg would the LS get if any?

If your interested in combining the small block bottom end with LS top end you should check this out
http://www.powerblocktv.com/episode/HP2010-07/chevy-hybrid-smallblock-build#.V4vErvkrLIU

[cstiles]

Fill her up drive it till needs more gas. fill her up again take miles driven and divide by gallons of gas used

Ok, good.

Do you know what your axle ratio is?

Not for sure .guy I got it off told me its 3.08 . but it may be 2.73