Technical 59 truck mpg"s

Hello once again. I made a post earlyer but got deleted and not sure why i changed the topic from mpg"s to what it is now. I have a 3/4 ton 59 apache with a list of all the new stuff i put.

Crate 350 long block 260hp
New tko600 .64od
Ram air air filter
Pertronix 3
Electric fan
1406 edelbrock carburetor
Timing 34 total
Full time vacume
=10 mpg highway

This set up has 460 miles on it. Do i have to wait a couple thousand miles before i get true mpgs? This is my first ever brand new motor to deal with so i really would like to know what you guys are getting and how? What am i doing wrong? This is driving at 65 highway about 2k rpm 2100 rpm new tires that are 31 3/4" and rear end i believe is a 4.56.

 

Rear end is the first thing I would be looking at. What fuel pressure regulator are you running and what is the PSI of your fuel pump (electric or on the block)? Four things you need to look at, your cam, your fuel pressure, timing, rear end gear ratio. All of these will play a role.

I run a 350, roughly 280ish+ hp (most of the same stuff you have on yours), 700R4 Trans (overdrive) that is built for 1300hp with a 3.90 gear ratio rear end, I have the same mileage as yours, and I do about 2100 RPM at about 75ish.

I can lay a decent line of rubber, do donuts to my hearts content, and give some punks in rice burners a run for their money. Ultimately, I don't care about MPG because I like the noise it makes when I mash the pedal to the floor.

 

Also, it was probably deleted because of someone getting upset that you aren't building it "traditionally" with stock parts or an era correct vehicle. This website was much better a few years ago when the rules weren't so stringent and people came together here to bitch about rat rods and street rods together, instead of segregating one another. Ahhh, the good old days.

 

It is important to know what mileage or economy is possible or typical even if in the single digits, if only to get an idea when a tune up is necessary or something is seriously wrong. Wasted fuel washes out rings and dilutes crankcase oil, fouls plugs and performance suffers, etc. Best performance is generally best MPG so what's not to like? For my part it's always been a matter of range that hurts, not so much the $$.

 

Totally agree.... and I get about 10MPG if I can keep my foot out of it..... if I were worried about gas mileage I would drive a Prius... my reservation would be that I would prefer to keep my soul and man card intact a while longer...

 

You could put a gun to my head and I couldn't point out a Prius or tell you what they look like, sorry lol!!!

 

I have a fuel pump on the block and it gives out about 3 1/2 psi. And i ask about mpg because i know alot of you carburetors are getting 16+ i was getting that in the old 283 that popped on me. And that was with no od tranny taching 3200 rpm at 65. I want to be able to take this on 3 hour road trips to reno, fresno ect..

 

The gearing of your rear end is killing your mileage...3.55 will help a bunch...I get 18 mpg..

 

Gearing and a better tune. I pulled 20mpg in my 54 Chevy with a similar setup. Final drive in mine was a 3.73

 

Since you have OD and tall tires the gear ratio may only be slightly suspect, especially given the RPM at the speed you recorded. So that brings up another point, the "best" RPM/Speed combination. As counterintuitive as this may seem, try to run a bit faster, get the engine into it's own happy spot. In my very low tech (no tech really) way you can sort of tell where an engine wants to be by the drone. As you gently increase speed there's a set of sounds the engine will make that lets you know where it wants to be. Sounds silly and childish, I know that, but it's there. Speed it up about 200 RPM or more and I wouldn't be surprised to hear it got better. It's possible that it's simply loaded just a bit much at 2100, and there's a weight factor involved. As I recall a 3/4 ton wasn't a light package to begin with, even in early trucks like yours. Good luck...

 

Her's a fact. The engine is most efficient at it's torque peak. If you are only at 2000 rpm at cruising speed and the torque peak is at 3000, you are killing the efficiency. You need to gear cruising speed to be in the range of the torque peak. Most of us that get good mileage just stumble upon it but you could plan for it. I have a C-30 with 350 and it had a TH400 and 4.10 gear, it got 10 mpg highway. Now It has an OD stick and gets 17.5 highway, same engine and rear, just got the engine slowed down to about 2300 at 70 mph. it was over 3000. too low rpm is as bad as too high at cruise.

 

Rt on 'pumper, torque peak. Since it's a crate I'd bet a cup of coffee there's some dyno "sales pitch" somewhere in the vast 'net wasteland. Armed with that you could taylor your gearing or driving habits to the peak TQ, or at least really close.

 

Maybe. Depends how the engine clearances etc. were set. Old time rough cylinder wall finish had a lot of friction until the rings bedded in. Even my new at the time 1996 Chevy pickup gained 2-3 mpg once it loosened up, and it took way over 500 miles.

 

We are building hot rods right?

When did we start worry about gas millage? HRP

 

You show 34* total adv. That's w/o the vacuum adv. , right ?? W/o vacuum adv. you could try 36-38*, just listen for "ping". W/vacuum you should be 46-50*.
dave

 

I have heard guys run more advance with ethanol, and some run less. Also to be considered is his advance curve, since running down the highway at 2K won't be at full mechanical advance.

 

Valid point !!
dave