That's what my 6cylinder v8 351 is getting around town with a C4 3.25 gears and 31s. If I get my other 2 cylinders back and my AOD tranny, I think I'll be knocking on the door of 15 or maybe more!

What do you guys get?

 

OD trannys, slowing these ol brick bats engines can help mpgs a lot. When most guys build their truck engines they want huge carbs that the engines can't handle so gasoline in vapor gets dumped out on the roadway, while driving along. They want to do burnouts instead.

Our trucks and engines are 1950s & 60s designed when gasoline sold for $.25 a gallon, and trucks WERE NOT driven except for work and were driven about 45mph on mostly dirt roads.

One nother thing, many change rear ratios, trannys and the speedo gear is not marking correctly.

So if you get everything working with OD 15mpg is doable.


John

 

Yea I had to change speedo gears a couple times from a 16, to a 17, to an 18 and now it's right on.

I'm confident I could achieve 15mpg with my OD tranny. I've got a 600 edelbrock so not too big on carb, and for best milage I could swap rods and jets.

 

what OD tranny will fit on a 429 block...I have a C-6 now and would like to lower the RPM's down at 55mph from 2500 to 1800 for cruising.

 

Gear Vendors overdrive bolts to your C6.

 

E4OD trans will bolt to your motor. Stand alone computers are available.

 

gears swap easily in the rear end you can choose whatever gear set you want and do so much more than trying to figure out the OD trans and their quirks .....351cleveland why is she only running on 6-ish? and with your 3.25 gears and 31's your setting on one great gear ratio already and if your motor doesn't have the extra torque to handle the lower rpms and keeping you at speed your motor will actually use more fuel then if you have it in the right power curve to provide the right power yet low enough rpm its not wasting fuel..... i know i get my best mileage with my FE in the 2000-2300 rpm range (65-75 mph area with my gear ratio) anything less or more and my mileage goes down..... (depending on your brand of tire 31 can be different actual heights) i have a gear/math deal done on your truck based off of the 31 i had which measured an actual 29.5"...anyway based on the info you gave (if your still running c6) multiply 0.0271 by what ever rpm you want and you have your actual MPH (2400 rpm is 65 mph W.I.P.) like i said you already have a great gear ratio for a 351w or 351c if you have an AOD with the .67 overdrive (2400 rpm would then be 86 mph) (1800 rpm is then 64 mph) which would be great for a big block or a nice torquey small block but on a stock 351w would probably be a little low on the rpms considering the 4000 lbs these trucks weigh.....i hope you get your 351 back on all 8 soon..... oh yeah end rant

 

E4OD. But you have to get a controller.

Yea it will be geared high with the AOD. But I want it to go down the interstate at 80 without screaming. If it's too high I'll swap the rear gears for some 3.70s or something of the like.

 

just for reference my 390 4 speed manual with 3:50 gears gets 13 pretty much every tank totally stock 4wd. 15 should be easy for you to attain. I'm gonna shoot for 17 when I start screwing with mine.

 

Eric, If you are getting 13 running 3.50 rears, you had better leave it the hello alone.


John

 

A-men! Although my engine is a performance build; with 3.54 gears and a light foot I can't get 10mpg.

 

If you knew me better, you'd know I can't do that

I just have to screw with ****. Besides some-one here told me a few years ago I'd never do better than 13, so I kinda have to.

 

'69 F100 2WD with 300 6 with C4 and 3.50 gears and I believe 27" wheels. 13.5 UK mpg in the 'burbs, 18 on the highway.

'77 Highboy with 429 and C6. Not sure on the gearing but the wheels are 33". 8mpg around town and 12 on a good day for the highway.

Again, it's UK figures, not US.

 

17MPG!!!!!!!!

That's what I just got on a 34 mile round trip. Empty one way, loaded about 1,000-1,500lbs on the way back.

Freeway both ways. About 60mph.

AND I GOT 17 MILES PER GALLON!!!!!!!

so I'm confident that knock on the door of 20mpg with the right tuning and an easy foot.

 

Still running on six cylinders?