BK wants a vette

Is anybody else only getting like 8 mpg from thier respective vette. I have a 1980 L-48. I realize I only have a 3 spd tranny, and am running 3:08's but oh my gosh. It's killing me. I think I can actually see the gauge moving as I drive. Before somebody beats me to it, I will give myself this one :nopity

MILO

I have a '79 L-48 with 3-speed auto and 3.55 gears. Moving from NY to NC I drove it and got 15-17MPG city/hwy. My carb is a holley with vacuum secondaries, Quadrajet operate in a similar fashion. If you do mash the peddle, the vacuum secondaries won't come on until the engine needs it. Double pumpers, carbs with accelerator pumps on the secondaries with always shoot a couple of cc's of gas.

Or your speedo may be off a bit.

BK wants a vette

I'm also running a holley with vacuum secondairies. Are you running @ 3200 rpm's at 70mph?

mayberg

Yep - 8 mpg for my big block. If I'm cruising long distance, it'll jump up, but around town (especially when I've got the pole position at a stoplight) I'm good for 8 or 9 mpg.

GTR1999

Doesn't sound like 3:08's at that range, if you still have stock tires. 355 or 370's maybe?

Gage

I sware my 72 350 3sp auto 3.08 rear gets worse mileage than my 69 427 4sp with 3.55s did. It is really weird. Maybe it is the fact that my 72 has an 18gal tank vs 20 gal on the 69 and it just seems like I have to get gas more often.

LiveandLetDrive

:withstupid: with q-jet and mods as listed below. Even for a little higher RPM, that seems excessively low. Have you checked your timing advance? I got horrible mpg before I realize my mechanical advance had frozen up completely. Also could be a carb tuning issue.

MILO

Yep, my RPMs are around 3,200 at 70mph. Since you have a holley the secondaries may be opening up at that rpm level.

I do have to admit I don't drive consistenly at 70 mph. Driving long distances 60-65 mph keeps me up with traffic and acceptable gas mileage. But when I'm in a hurry, I pay the price -- gas mileage.

I suspect its more than driving habits causing the problem.

Buffalo Dude

That doesn't sound right to me either. Cruising around town I get 11-12mpg, freeway I get ~15mpg. 8mpg is like if I did WOT starts at every light. Maybe time for a tuneup?

pillowmeto

76 L48 and a T350 and 3.08s here, getting 8-10 :rolleyes:
going with a super T10 four speed this summer and hopign that will help, plus the engine will be spiffed up, alot

MAtt

guppie

I never wanted to know, so I've never checked mine. I didn't buy it for economy so I try to stay in the dark on that subject. :cheers:

redwingvette

quote:
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I'm also running a holley with vacuum secondairies. Are you running @ 3200 rpm's at 70mph?
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Doesn't sound like 3:08's at that range, if you still have stock tires. 355 or 370's maybe?


:iagree: When I changed from 3.08 to 3.55 that is what I seen. I got 11mpg on long trips. That is why I whent to the 200-4r. Now I can cruise at 70mph at 2200rpm.

UKPaul

If it's any help I was doing 70mph @ 3000rpm with my Th350C TCC unlocked (so it'd be the same as a stock Th350?) and I've got a 2.87 rear ratio.
:cheers:

Beer

I'm with everyone else, that is just too low. I'm getting 10 to 12 in the city with my modified 81.

Corz

I get a whopping 0 mpg.. stop complaining and drive it, I wish I could drive mine.

When it works I get about 12mpg out of a 327 with a TH400 and 3.08s

Jasonty

383 stroker, Carter AFB 650 CFM carb... 2.79's in the rear, and I'm STILL getting about 10 mpg... When I feel like driving the car hard, I get around 7 mpg. Oh, it's gonna be dangerous when I get my 3.90's installed. I'll have them in there for at least 3 months before I get a 200R4 installed... 81's were supposed to have that lockup torque convertor, TH350C, but when I pulled my tranny, I realized it isn't the original. Just a plain old TH350. That's not helping with the gas mileage!!!...

BK wants a vette

Thanks so much for all the input. So here's the big question: Do I swap out the gears to a different ratio, or bite the bullet and upgrade to a 200R4 or 700R4. Also what about the long term value of the car in terms of not having correct/ original components even though the car is more drivable with the different transmission? :)

redwingvette

"Also what about the long term value of the car in terms of not having correct/ original components even though the car is more drivable with the different transmission? "

Who cares! Its my car and if I can't enjoy it then I might as well get rid of it. To each his/hers their own. :auto: :)

Jasonty

Agreed... I didn't buy this car or mod it out just to worry about it's value if I ever try to sell it. Also, going to a higher (numerically lower) gear ratio will make it noticably slower off the line. I have 2.89's, and I get taken off the line by V6 Mustangs, just because they come with 3.27's and 3.55's... That's why I'm saying hello to a fresh set of 3.90s. Intalling a 2004R transmission is a snap. I know for sure 80 & 81 Vettes require no drivetrain modifications, not sure about other years. It has better spaced gears then the 700R4. Great upgrade, IMHO. Get 3.90's, get a 2004R, get better gas mileage, and get better response off the line... Good luck!