How many MPG does your C3 get?

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Mar 3, 2011 | 10:20 PM

#81

LancePearson

Drifting

Joined: Oct 2010

Posts: 1,972

Likes: 6

From: Chester Virginia

Quote:

Originally Posted by fauxrs

The rear gear is a 3.70:1 with the 5th gear it calcs out at about a 2:50 in 5th gear (0.68:1 OD). Yes freeway alone I get better mileage, the 21 quoted was city/fwy combined. My RPM's at 70 went from like 3500 to 2500.

However the 1st gear is lower and I suspect the 5spd actually hurts my city mileage...TBH I have only tracked mileage maybe 2-3 times in the time ive owned this car. I should point out the 1st time I calculated mileage was before I had the 5spd, then with the 4 spd and the 3.70 I was able to knock down 20 on one freeway leg of a cross country trip, that was driving for mileage.

I see you are in Chester VA. I bought this car when I was living in Roanoke.

Thanks for the info. I feel better now as it makes sense. My carb could be tuned better but it's not all bad. With my 3:36 rear end and M21 tran. at 70 I'm doing about 2800 rpm and tires that measure not 27" but 26.25" diameter so with the fifth gear o.d. but slightly offset with the 3.70 rear end and your observation that the 5th gear dropped rpms at speed by just under one third, it makes sense. Isn't that to some extent what the newer modern vettes do to get 20's mileage...better gears with enough power to handle low o.d?

Been in Roanoke many times..also sailed three times to Mexico from San Diego, family just up the road there at one time and been there many times. Raced Wed. nights several times from the San Diego Yacht club down by Pt. Loma. I like San Diego, Rancho Santa Fe, La Jolla, Vista, etc. Great place to live if you can afford the freight to buy a home there!
Lance

Mar 4, 2011 | 12:08 AM

#82

jay73BB

Intermediate

Joined: May 2007

Posts: 44

Likes: 0

From: monroe oregon

my 73 big block 4 speed with 3:36 gears gets about 12 mpg the all stock 67 435horse with 3:55 gears gets 15 mpg. i am thinking about getteng a 5 speed kit for the 73

jay

Mar 4, 2011 | 12:21 AM

#83

PLRX

Team Owner

Joined: Aug 2005

Posts: 34,988

Likes: 515

From: Riverside County Southern California

Co-winner 2020 C4 of the Year - Modified

2018 Corvette of Year Finalist

2017 C4 of Year

2016 C7 of Year Finalist

St. Jude Donor '09 thru '20

Quote:

Originally Posted by MN80Vette

Thats funny

Mar 4, 2011 | 01:34 AM

#84

MakoShark72

Safety Car

Joined: Oct 2006

Posts: 3,993

Likes: 9

From: Gig Harbor WA

16 city, 24+ highway...

ZZ4, 2004R, 3.08 rear, Holley 670 Street Avenger, Hooker sidepipes

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Mar 4, 2011 | 01:40 AM

#85

dacfan

Racer

Joined: Oct 2010

Posts: 278

Likes: 1

From: Ware Shoals SC

Abt 8 mpg here. Edelbrock carb is out of whack but I've been driving it until I can find someone close by that can tune it better than I can and school me on what I'm doing wrong

Mar 4, 2011 | 09:58 AM

#86

emmvette

Instructor

Joined: Jan 2009

Posts: 187

Likes: 1

From: Central IA

Quote:

Originally Posted by LancePearson

What would you be turning for rpms going 70 mph on the Interstate cruising? My l48 350/180 with M21 turns about 2850 rpms at that speed plus or minus a little with 3:36 rear end. I presume yours would have to be higher?

Lance

Lance,
About 3,200 at 75 mph. That is why I don't drive it on the interstate. My car has the original drive train, never been rebuilt, and has 38k miles.

Mar 4, 2011 | 04:51 PM

#87

LancePearson

Drifting

Joined: Oct 2010

Posts: 1,972

Likes: 6

From: Chester Virginia

5 speed

Quote:

Originally Posted by emmvette

Lance,
About 3,200 at 75 mph. That is why I don't drive it on the interstate. My car has the original drive train, never been rebuilt, and has 38k miles.

Is the Tremec 5 speed a kit to convert your existing Muncie M21 or a whole new transmission? I'm not exactly clear. the 5th 0.68:1 gear sounds appealing for highway use.

Lance

Mar 4, 2011 | 05:14 PM

#88

SHOWME

Pro

Joined: Apr 2006

Posts: 719

Likes: 2

From: Lawson Missouri

Quote:

Originally Posted by LancePearson

Is the Tremec 5 speed a kit to convert your existing Muncie M21 or a whole new transmission? I'm not exactly clear. the 5th 0.68:1 gear sounds appealing for highway use.

Lance

It's a whole new tranny.
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