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Posted: Fri Aug 29, 2008 4:49 pm Post subject: Can I improve gas mileage?
im a college student, and i'm buying another car in a few months (68 camino). now i don't really know much about older american cars so thats why I want to ask YOU guys
the question is simple, i just don't want to get 13 mpg Instead, 18/19, that would be great. I did read this one article quite a while ago, they were talking about adjusting the carb, and there are certain adjustments that gives you less power but alot better gas mileage. i also read that having 3.0 gears also increases gas mileage (idk wth that is btw so if someone can plz elaborate on that)
that was just one thing i read though...
so do you guys think that 18 mpg for a v8 is possible? what about v6? i really want to know because I really want an el camino!!!!!!!
Necoa #: 10934
Location: 15(AZ,NM)
Joined: Feb 03, 2008
Posts: 457
Year: 1981
Model: El Camino
Posted: Fri Aug 29, 2008 5:23 pm Post subject:
Sure, its possible. But there are a lot of variables involved besides just a V-8 engine. State of tune, what size engine, what transmission, front end alignment, rear gear ratio as you mentioned, lots of things. As for the carb, you can make adjustments to improve fuel economy. But I dont think you'll see a big improvement in mileage unless your carb is really in bad shape. We need more info on the car to give you some pointers to improve mileage. Post more info on the car if you can.
For a '68, it's going to be hard to get the economy you want.
As for the gears, back then the "economy" axles were ~3.0 (or high 2s), which will have you wasting a ton of gas on the highway. The 5th gens have ultra-high 2.2 to 2.4:1 axle ratios. That'll give great cruising economy, but it kills off the line performance. The remedy is to have something like a 3.5x axle and a 4 speed overdrive transmission. Of course, with a high axle and 1st gear, the ability to rev the engine to redline at every stop is not going to help econ.
Chevy didn't have a V6 until 1978. You'll be looking at an inline 6, which should get a bit better econ than the V8s. Not sure what they actually get, probably high teens if you're careful.
If you really want economy, a late model computer controlled drivetrain is the way to go. For example, the '94-'96 Impala SS LT1 gets over 20 mpg highway, although the very good aerodynamics helps that a lot.
Necoa #: 6381
Location: 7(AL,GA,TN)
Joined: Nov 02, 2005
Posts: 1034
Year: 1986
Model: El Camino
Posted: Fri Aug 29, 2008 11:45 pm Post subject:
It reslly comes down to gearing. sure, you need to have a good tune and keep tires inflated blah, blah, blah. But those are just common sense things. what will really help is having a 3.08 rear end with an overdrive transmission with a finsl ratio of 0.70:1 or higher.
such transmissions are:
Auto:
700-R4
200-R4
Auto electronic (for computer controlled engines):
4L60E
4L80E
6L60E
6L90E
there are more of those...
Manual:
T5
T56 double overdrive
there are others available aftermarket.
the T56 has the highest overdrive of any transmission... 0.5:1 , so even if you have a 4.11 rear end with a T56, It's like having a 2.29 with the stock transmission in a 68.
there are guys on LS1tech laying down 320+ HP (stock SS/WS6) with the T56 and stock 3.42 rear ends that get 30 MPG. How's that sound? _________________
Formerly 86Conquista
Currently undergoing resto.
Planned:
-350/?/3.42
-ZQ8 wheels
-Disc Brakes
-More
Posted: Sat Aug 30, 2008 4:25 am Post subject: Re: Can I improve gas mileage?
jammy wrote:
...i also read that having 3.0 gears also increases gas mileage (idk wth that is btw so if someone can plz elaborate on that)
3.0 gears refers to the rear axle gear ratio. In the example you gave, this means 3.0:1 (3.0 to 1). The rearend gear ratio refers to the relationship between the ring gear and the pinion gear. By simply dividing the ring gear tooth count by the pinion gear tooth count, the ratio is determined. For example, if we divide a ring gear with 41 teeth by a pinion gear with 10 teeth we find that the gear ratio is 4.10:1 (41/10 = 4.10).
For better gas milage cars can be equiped with "taller" gears like 2.73:1 which will also decrease performance because the engine is running at the low end of its power band (running slower) while cruising. But for better performance, you may choose "shorter" gears like 4.10:1 which will also decrease fuel milage significantly because the engine has to work harder (run faster) to keep maintain cruising speeds.
However, as stated in some of the posts above, transmission gearing, wheel diameter and engine size/setup will also play a huge roll in determining fuel mileage and/or performance, not to mention how you drive the car. I can get 2 - 3 mpg increase on a trip if I drive mine like my Grandmother would, but that's no fun for me.
18 mpg with a V8 is possible... I guess, if you tuned it to within an inch of it's life and never get into the throttle too much. You would be more apt to get that kind of milage from a V6 in a much smaller (lighter) car. El Camino's are about the same weight as your average Chevy S10 or Ford Ranger pickup. _________________
1981 Chevy El Camino
1991 Chevy S10
"The only thing collecting dust in my garage... is my broom"
Necoa #: 6381
Location: 7(AL,GA,TN)
Joined: Nov 02, 2005
Posts: 1034
Year: 1986
Model: El Camino
Posted: Sat Aug 30, 2008 11:30 am Post subject:
18 mpg isn't hard to come by. I got 18-19 with my stock (well, exhast/intake) 305/200-4r/2.41 drivetrain. I got outrun by a stock f150 with a 302, but I got good gas mileage.
that was without the lockup torque converter working. _________________
Formerly 86Conquista
Currently undergoing resto.
Planned:
-350/?/3.42
-ZQ8 wheels
-Disc Brakes
-More
Necoa #: 2321
Location: 15(AZ,NM)
Joined: Jan 30, 2004
Posts: 1169
Year: 1974
Model: El Camino
Posted: Sun Aug 31, 2008 9:12 pm Post subject:
I was getting 18 to 20 with my original gears in my 74 (The big El Camino model) but I had 2:78 gears and a TH400 which has a less aggressive first gear than a TH350.
When I changed my rear gears to 3:42's My mileage dropped to about 12MPG. I need to get another gear either with a 4speed Auto, an overdrive unit or a 5 speed manual setup.
Gearing will have a lot to do with mileage. I'd say if you want mileage but still want to have fun I'd go with an overdrive transmission or a 5 speed manual. That way you have more control of your fuel economy just by how heavy your right foot is.
I have a 2008 Mustang GT with a 5 speed manual. I know it's got way more engine management than my Elky will ever have but still it's a V8 and I'm getting about 24MPG right now. That holds so long as I keep my foot out of it. If I have too much fun I drop to 18MPG fast.
_________________ 74 El Camino Classic - project car #1
96 Camaro - RIP, Traded 10-16-2007
2008 Mustang GT, It ain't a Chevy but at least it's American!
Well I have a small block 305 and I seem to get like 20s miles to the gallon. As long as you do not drive if fast and just cruise around in it, then you should be alright with gas _________________ El Camino Nation the second best El Camino forum on the web http://elcamino.freeforums.org/portal.php
so it boils down to the gears, tranny, and of course driving style.
Now some of you stated about different tranny's. If I were to, for example, throw in a T5, how difficult of a process would that be? I've replaced (or actually helped replace) one tranny before, it seemed easy, the hard part was putting in the new one, but this was done on a 3000gt (asian car in other words)
And what about gears? I would imagine that would be easy, but I have no idea
Changing from an automatic to a manual is a lot of work and finding some of the parts necessary to do it is not easy---your model is probably one of the easier ones to do and have the most parts available to do it so I say go for it......but if you want to get some real gas mileage, you would do much better with converting it to fuel injection---now having said that, that is not a simple thing to do nor is it cheap so thats a commitment that should only be taken if the vehicle in question is worth it and you plan on keeping it a long time....I have done it a few times on my vehicles and each one has been a challenge..........Dan _________________ I don't think I have ever had a car that was "FINISHED"........unless it was totaled.
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Instead, 18/19, that would be great. I did read this one article quite a while ago, they were talking about adjusting the carb, and there are certain adjustments that gives you less power but alot better gas mileage. i also read that having 3.0 gears also increases gas mileage (idk wth that is btw so if someone can plz elaborate on that)
