Tcheairs38655

I've got a 383 Stroker (10:1 with Dart heads) in my 66 with a properly tuned 650 Holley vacuum secondary carb and MSD Pro Billet ign system. I'm getting an average of 9/10 mpg on 93 non ethanol gas. I don't "punch" the car often and most cruising down the road is done at 3-35K. (370 rear end) Can anyone confirm that my mileage is in the ball park?

I was getting better mileage that that in my previous 427/425 matching numbers car

MikeM

That is just a little more mpg's than a loaded dump truck gets.

SWCDuke

High overlap cams = lousy mileage. How do you know your carb is "properly tuned"? It doesn't make any difference what kind of wazoo ignition it has if the spark advance map is not properly suited for the engine configuration.

Large displacement and a low overlap cam = big torque at low revs, and since most engines (except with big cams) operate most efficiently at low revs/high load, you should shift at no more than 2000 in normal driving, but you say your cruise at 3000-3500, but didn't say if that's around town or highway.

You may be like some guys I know who drive their car around town in second gear all day like it's a two-liter Porsche and then complain about fuel consumption.

Duke

GTOguy

The 383 in my '61 with original dual quad WCFB's and a healthy cam gets worse mileage than either of my GTO's....by a bunch. I probably get 12-14 mpg.....same gear as you, 3.70 with stock bias ply 15" tires. It does, however, pull like a train.

wmf62

NICE... IF you're pulling trains....

Bill

GTOguy

I'll have to add, that my mileage figures are pretty much 'in town' driving. Have yet to take the car on any long highway trips. I tend to keep the revs down (most of the time!).

wmf62

I have kept a spreadsheet for the corvette. I have had only 327s/350s, with a 3.36 rer, and with or without OD, and all with some version of fuel injection.

over 58,003 miles I have AVERAGED 18.19mpg...

Bill

Tcheairs38655

The 3000 to 3500 is what it takes to get between 60 and 70 mph on the highway with the 3.70 rear end. The gross lift on the cam is 550 and the tappet life is 280. Duration at 050 is 236 deg. lobe lift is .3666. lobe center separation is 110. One caveat, I'm not using the vacuum advance, only mechanical. the curve is 1deg at 1400...5@1800...8@2000 and 12@2800. initial timing is 14@idle (900rpm) and 38 total@3000 vacuum advance disconnected.

Somebody's getting 15mpg with an L-79..I'm running the wrong motor.

MikeM

You're not running enough timing is one problem.

TWINRAY

Well it wasn't a Corvette but it did have a 4 bbl 350, my 1977 K5 Blazer gave me 6 mpg before I just parked it in the mid 90's.

GTOguy

That's familiar. We had a '69 Suburban in the '70's with a 350, 4bbl, TH400 and 3.73 gears that got 6-9 mpg. It was sure tough, though.

kingwoodvette

14* initial + 12* max centrifugal= 38* total ?

SWCDuke

Too long duration and too much overlap cam... no vacuum advance... short gears... no wonder it's a gas guzzler.

As already pointed out your centrifugal advance data makes no sense, but if you are quoting dist. deg. at engine RPM, it would make sense.

Duke

Crunch527

Those heads will probably allow a few more degrees of timing...in my 383 with AFR heads and 10.5 compression...can't remember the cam specs...big, overlapped, and lumpy...it liked the additional timing...

What color bushing do you have in the dist? I ran the smallest...black one I believe...the blue bushing that comes with the MSD wasn't quite right...

Gas mileage? Don't care...never added it up...

Tom Austin

I drove my '66 L79 roadster to Pittsburgh last year (242 miles each way) . . . and with the cruise set on 72 mph, I averaged 18.6 for the trip! (4.11 gears with .63 overdrive) I was happy with that number!

LT1driver

67 435 with 3.55 gears got 15 @ 70mpg for me back in 70s on freeway

Crunch527

Its also the springs on the MSD Dist...I think I used the lightest silver springs...gets the timing in early...

I did all the "book" stuff on tuning and then tinkered to figure out what my engine liked best...

capevettes

My 61 with a 383 stroker gets about 10-12 mpg around town and maybe 16 on the highway, but I have a 3:08 rear. The car still makes plenty of low end torque.

You are probably getting about what I would expect with 3:70's. But it's not like we are commuting to work in these cars. So, who cares unless you feel it's not running properly.

Mike Terry

No matter what the Gas Millage is if you really car and can't afford to but gas for your Corvette, then maybe you should not be driving it. To me Gas is the least of expenses that a mid year Corvette could have.

wmf62

some of us need to budget, not everyone has the $ to build Motorama cars

Bill