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Joined: Jun 2012
Posts: 197
6
Shop Shark
Shop Shark
6 Offline
Joined: Jun 2012
Posts: 197
Alright, I put 114.4 on the clock since I last checked it, and the results are in. I bought exactly 5.00 gallons in a can to check, and it was 30lbs worth of fuel; so the scale and math works.

In 114.4 miles of mixed driving, driving normally, I atomized 7.9 gallons of 87 octane with that little Rochester 2 bbl; for a total of 14.5MPG.

I'm pretty happy now, the truck drives great; and 14.5MPG I can live with. Only "mod" to speak of is that I bumped the timing up. To 12 degrees initial, IIRC. Carb is stock jetted, idle mixture screws turned in a bit lean from max RPM/vac reading for economy. The engine is a 195HP 283, the 2 barrel car version with the small chamber "power pack" heads. Rams horn manifolds running to a y-pipe and single small outlet OE type muffler. Transmission is the wonderful, indestructible, SM420 truck four speed. I think the rear gears are 4.10, with a 7.50-17 bias mud tire @ 620 revs per mile.


Some of my crap:
1963 C-30 flatbed dually 292/SM420
1965 C-10 LWB fleet 250/column shift 3 speed
1965 C-30 9' stepside 250/SM420/4.10 gears (my DD)

Website I made for my crap:
http://www.66submarine.com
Joined: Apr 2013
Posts: 24
P
New Guy
New Guy
P Offline
Joined: Apr 2013
Posts: 24
Wow 14.5 I can't get over 10 with my 66 C30 with 292 thats great milage with that truck what kind of bed on your truck mine is a dump

Dave

Joined: Jun 2012
Posts: 197
6
Shop Shark
Shop Shark
6 Offline
Joined: Jun 2012
Posts: 197
Mine's a 9' stepside pickup. I have some pictures of it here: photobucket link



Some of my crap:
1963 C-30 flatbed dually 292/SM420
1965 C-10 LWB fleet 250/column shift 3 speed
1965 C-30 9' stepside 250/SM420/4.10 gears (my DD)

Website I made for my crap:
http://www.66submarine.com
Joined: Apr 2005
Posts: 313
D
Shop Shark
Shop Shark
D Offline
Joined: Apr 2005
Posts: 313
My first truck was a '66 C-30 9' stepside, and it got around 14mpg.

Joined: Sep 2012
Posts: 28
W
Wrench Fetcher
Wrench Fetcher
W Offline
Joined: Sep 2012
Posts: 28
I have a '63 C30 Dually. 250 straight six, SM420, Dana 70HD with 4.10s out back, 235/85R16 tires (31.7" tall). With a steel flatbed I average about 12mpg. When I first got it on the road with the bare frame rails I got about 15.


1963 Chevy C30 - 292 I6 +.040" 10.78:1, SM465
1978 GMC K2500



"Four gears with a granny low and six cylinders straight in a row."
Joined: Jun 2012
Posts: 197
6
Shop Shark
Shop Shark
6 Offline
Joined: Jun 2012
Posts: 197
I'm running 235/85r16's now, too. I just bought a '63 C-30 dually yesterday, BTW. $400 and it even has a 292 and a hot battery! Hoping to get it running soon. Anyway, I pulled it back home on my crappy little 16' car trailer behind the '65. The fuel tank wasn't all the way full when I left, and something like 160 miles later I arrived home with some fuel still left! Must have got 11-12MPG or something. Really surprised me! I drove slow, but there were many, many long hills that I went up wide open all the way, some times I drove in third gear because of heavy rain (or hills), and I wasn't afraid to downshift and use the engine to help slow the rig down. GCW was 12,000lbs+.

Last edited by 66Submarine; 07/04/2013 7:35 PM.

Some of my crap:
1963 C-30 flatbed dually 292/SM420
1965 C-10 LWB fleet 250/column shift 3 speed
1965 C-30 9' stepside 250/SM420/4.10 gears (my DD)

Website I made for my crap:
http://www.66submarine.com

Moderated by  Hambone, Woogeroo 

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