Smokehouse69

Just completed my first "long" roadtrip with the new engine. I'd made several 60-80 mile round trips, just cruising during the first 500 miles I had on the engine, but I was concentrating varying my speed and other tricks you are supposed to do while breaking in a new engine.
I went to my parents home near San Antonio, which is 110 miles from my home. About 90 of those miles are 70 mph highway, the rest is stop and go through several small towns. My round trip from fillup to fillup was 242 miles and the car used 13.4 gallons of gas, for an average of 18.06 mpg!!! This is for a tight new engine, TH400, 3.08 rearend car! Of course I'm running a really tiny Holley Economaster carb on the car right now, but I didn't baby it during the drive. On the highway I ran between 70-80, with a couple of runs up to 100+.
I know I probably won't see these kind of numbers again after I put on the Holley 650 DP, but it was nice to now that old technology when tuned right could get decent gas mileage without using a computer or overdrive transmission.
P.S. I found out where the car shifts out of 2nd at WOT 100+mph and 5600+ rpm, I really need to adjust that governor!

SanDiegoPaul

I found out where the car shifts out of 2nd at WOT 100+mph and 5600+ rpm, I really need to adjust that governor!

Sounds about right to me! :yesnod: :blueangel:

Chuck Harmon

Smokehouse,

You've got a really nice setup. The 18+ doesn't surprise me in the least. Even with the 650dp you should be able to duplicate those numbers and higher on a steady cruise. With the dp you will find that the instant throttle response will make you think you've got an extra 50-100 horse power under the hood when you nail it. That is what you get for the extra cost of more fuel RIGHT NOW!

On the highway, I was getting 22+ with my L46 4 speed, 3.36 gears and a 800cfm Holleydp spreadbore. this was at steady cruise, no secondaries kicked in. The dp won't hurt your steady cruise mileage, only when you nail it. What you may lose in mileage, you will gain in grins!

The trip computer on my Z shows 28.5mpg average with close to 2:1 overall gear ratio while crusing for a couple hundred miles on the highway (70-80mph), but when I pull off the highway and cruise around town for 1/2 an hour sitting at lights, etc, the average drops to about 23, about 5mpg loss. I am sure that your mileage was probably closer to 23+ on the highway.

Chuck

SmokedTires

That's very :cool: ! 18+mpg is better than many new trucks :D .

Smokehouse69

The best I ever got with my 94 5.7 Chevy truck was 19 mpg and this was when the speed limits were 55 over a 300 miles of highway driving. Since then I have been averaging about 14 50/50 highway and city. I hear the newer trucks do a lot better than that. I am extremely please with the mileage that I got with the car on the cruise.

SanDiegoPaul

:cuss Please! Can you teach MY CAR THAT?? :smash: :cuss :cuss :cuss

Yellow79

oh my god. i get 9... no joke 9 miles to the gallon on the highway. i calculated it two or three times because i thought i screwed up somewhere. then again i guess the 850 carb might have something to do with it... but i wouldnt think it would be that bad! and i have checked its not washing down the walls and according to the mechanic its fine and the engine can use the fuel its delivering... oh well. anytime you want to trade gas bills give me a holler :D