Anyone out there getting decent mileage in your bump sides? My 352 3 speed with headers and a 3.25 rear end got 15 highway going 65 BEFORE I put my headers on. I think that is not too bad for tech that old. Heck, my gmc ( hey, I couldn't pass up the deal!) can only manage 16.5 holding her at 60. My headers and ignition are only two months old, and I haven't gone on any long trips, yet. I've had 2 other bump sides. My '68 390 f250 was a pig. I got 10. And my '70 4x4 300 4speed got 13. I can't remember ratios on the other 2, but I'm curious if anyone out there is getting fairly good mileage with your setup. Let me know your combo and mileage! Maybe some of us are bucking the system!

 

In my 72 (avatar) c6 3.25 gears also with the .030 390 and headers got 14 the 300,000 mile 352 got 15 with headers and stock 390 got 16 with headers......when that 352 was in smokenchoke it only got about 12 due to the stock exhaust i swear and the 3.50-ish gears....... in my 66 i get 16+ with a 71 360 with P&P heads/intake and headers the 2.75 gears and the 435 np make it happen

 

I was able to achieve 17mpg a few times with one of my previous 351C engines. My truck has a C4, 3.25's and 31x10.50 tires.
But now that I have a cam and 4 barrel, I'm only seeming to get 12mpg around town. I haven't been down the highway much yet, but it doesn't seem to get any better than 12. (But I haven't really tried yet.....)

I'm in the process of building an AOD trans to swap in the truck. That should help a lot. I'm also going to jump down to 3.89 gears. But that will still see a 600RPM drop.

I have a K&N air filter that I'll be installing soon. (As soon as my current filter gets dirty)

I want to get headers, but I will have to have them custom made, or at least chop up some. (Never was a 351C in a truck, so nobody makes them)

My goal is 20MPG. Laugh at me if you want, but I believe I can do it with the right combination....

 

I had a 351C 4bbl in my '72, with headers. I took it out of my '72 Ranchero to swap into the truck, headers and all. I found the smaller bolt-in front crossmember to be in the way so I removed it, planning to eventually notch it or otherwise modify it to fit but never got around to it. Then I got a '77 Dent parts truck with a 400 with headers and was planning to swap the heads for my 4bbl heads and see if those headers would clear any better. Never did get around to it. I never actually checked the mileage in that truck, I think I was getting around 12. 3.73s and C6, Holley 1850 and Duraspark conversion. My '68 with a 360, 3.73s, T19 and Gear Vendors O/D, Edelbrock Perfomer carb and intake and Duraspark has never gotten better then 11.

 

TigerDan are you calculating actual miles or odometer miles because once you swap your GVO into overdrive you are going a further distance per revolution than just the regular t19.... so question is what gear ratio overdrive is in the GVO?

 

Actual miles as per GPS.

 

I think that Eddy Performer carb is the reason you didn't get better than 11, Dan. Eddys are rodded and jetted pretty fat out of the box. As you know,otherwise that O/D should have helped more than netting 11.

 

It was about the same with the Motorcaft 2bbl that was on it originally, and again with a Holley 500 2bbl. But yes, I'm sure there's room for improvement with the Edelbrock. At one point I was even playing with an old Holley 465 cfm 4bbl...talk about crisp throttle response! But it's all moot really, I'll be dropping a Cummins 6BT in it when I find a tranny I like (at a price I can afford!)