Checked mileage on my 66 1500
 

Well, I had to know and wish I didnt...checked the mileage on the 66 couple days ago and granted, she needs a tune up, I wasn't expecting what I got, nor was I expecting 15-20 mi/gal either. However, I checked it after running g around town a few days and 6.35/gal is all I'm getting. Yes I did the math 3 times and cane out the same every time. So how about anyone else, how good/bad is your mileage. I'm running a 350 with sm420 behind it...tell me it's gonna a get better after a good tune up lol. My financial advisor (wife) "advised" me to get better mileage or we both are headed for scrap yard.....

Re: Checked mileage on my 66 1500
 

Say it isn't so, Dave! If you absolutely have (per your wife) to get rid of the truck, find someone who will give it a good home!

Re: Checked mileage on my 66 1500
 

My truck average about 12 mpg, mixed city/hiway driving. This is base on six years of driving.

Re: Checked mileage on my 66 1500
 

350 V8 you say? Or 351 V6? We like the V6's, not so much the Chevy V8.
Anyway, with the 305 V6 most get between 11-13 MPG. Figured the 351 is about the same.

Have you checked the mechanical and vacuum advance on your distributor? Both should move freely, and the vacuum advance canister should hold a vacuum.

Re: Checked mileage on my 66 1500
 

It's a 350 v8, prev owner swapped the motor....

Re: Checked mileage on my 66 1500
 

That's a shame. SBC's are used often to replace the V6 - not much class in a 350 small block - the least a person could do is use a period correct SBC like a 283 or 327 and keep a little face. But a BBC wouldn't be too bad of a replacement - at least it would give the altered GMC a little more of a shine than being transplanted with a run of the mill SBC. :ohgeesh:

Re: Checked mileage on my 66 1500
 

I agree completely, a 327 would've been nice, even a 383 would've been better. The bright side, I know 350's front to back top to bottom, easy to work on...

Re: Checked mileage on my 66 1500
 

And don't worry George, she loves us both too much for the scrap yard lol. Thankfully, I sure would miss her ;0)

Re: Checked mileage on my 66 1500
 

Have you checked the advance in the distributor?