I know if I had a 4th gear, I would get almost double what I am getting now for mileage. Has anyone ever heard of someone putting a 4speed auto into a Bronco like mine?

 

We have already established you have a torque monster, you need gears far less than I do..
Dude, im stuck with a Windsor, your motor stayed popular with Motorhomes and one tons and fleet vehicles for years after they went out of style in the consumer truck, mine eventually got cut down and stuck into a Mustang!

Seriously though, I noticed that I can just BARELY stay at 55-60 in overdrive with 35s.. around town I barely touch the gas anymore.. I know everyone says regearing means death to mileage, but it's a fine tuned system.. I would guarantee!! 4.56s would improve my mileage on the highway, 4.88s are my sweet spot, I just know it!

My motor might be spinning 1400rpm on the highway now, but I'm at half throttle, ya know?

just bought an accel coil and a set of accel wires, it should improve matters. Slapped my old MSD on and it improved lowend in town, but on the highway I got a miss or crossfire.. checked resistances and secondaries are at like 3k OHMs! yeah, dropping that MSD in the garbage with two out of 8 of the Ford Racing plug wires that crapped out on me! Funny thing when brand perception doesn't match actual quality! Got my old, 227,000 mile Motorcraft coil on there. Would have bought another but I doubt the same people make them that use to back in 1990!

 

Yaaa I dunno what RPM i am at on the freeway, i got no tach. But i kknow i do have to hold the throttle firmly to stay up to speed and i rarely take it over 60 due to it being unpredictable.

 

I don't have a tach either but I can tell from the sound of my engine, that my truck is at at least 3500rpms or higher when I'm at 50mph or faster.

 

Oh yeah, C6, no overdrive! Honestly, it's pretty low.. I do know this, I use to only barely touch the pedal to stay at 60 with 31s, now it's almost half throttle.

It's not just RPMs, but intake velocity which judges how much fuel is pulled through, which means throttle really dictates your gas.. old knowledge, but with EFI people think it's all about RPMs.

by the way, i took my ol' girl to 90 the other day and wasn't at full throttle. Even with 35s I think and hope I'd top out above 100

 

Man i would be terrified to go over 70 in TGM, it shakes and bounces so violently i would poo myself... In my ranger i topped out at 90 with a 5 spd, i'm sure i could have pushed it but with a 2.9 that is known for warping heads when overreved i didn't want to go too far, but i can say it was fun.

 

probably just tire balance man, it's a pain getting 35+'s balanced

 

You can pretty easily figure your RPMs if you know your speedometer is correct.

RPMs = (Speed * Transmission Gear * Final Drive * 336) / Tire Diameter(in)

So, if you have a C6, 3rd gear is a 1:1
I don't remember your gearing or tire size, but I'm just going to calculate for 3.55s and 33" tires.

RPMs = (65 * 1 * 3.55 * 336) / 33
RPMs = 77532 / 33
RPMs = 2350

 

Once, years ago, on an open stretch of freeway, with no headlights in sight, I brought the Mustang I built up to 160 mph. (calculated by the tach and 3.10 gearing) And it got there pretty fast. That car gets 1-2 mpg around town, and burns only premium fuel, so don't feel too bad about your truck's mileage!

 

I hear ya on that, except mine doesn't shake that much...I just HATE how loud she gets when I have her that fast.

 

I don't mind the noise, i am generally around loud noises so i don't mind, it is just the thought of losing control of it going that fast

 

Well when she is screaming that loud, I'm afraid I'll blow up the engine...I know that would prob NEVER happen but it still scares me.

 

Has anyone heard anything about the Holley EFI kits? I'm wondering if I put one on, I'd get better mileage.

 

For optimum efficiency, this is the formula:
Engine volume (cubic feet per minute) = Engine RPM X engine displacement (cubic inches) / 2 volume per revolution / 1728 cubic inches per cubic foot.

A 351 engine running at maximum RPM of 5500 RPM with 100% volumetric efficiency would be:
5500 X 351/2/1728 = 557 CFM (cubic feet per minute)

However, an engine isn't 100% efficient. The Volumetric Efficiency(VE) in a stock street motor may be 75%-80%, a high performance motor around 85%, an all out race motor perhaps 95%. So, for your stock 351 engine, you can figure the required carb size base on a 75% VE:
557 CFM X .75 = 418 CFM.

Therefore, if you bolted on a Holley 490 4 barrel carb on a stock 351 with aftermarket 4bbl intake, your stock Bronco would likely see an increase in MPG, and also an increase in low end torque. I prefer carbs over fuel injection, and properly set up, a carb will rival FI in efficiency with 1000x more simplicity. 4bbl intakes are more efficient than the stock 2bbl intakes because they distribute the air/fuel charge better among all 8 cylinders.

Also, from my experience, Holley carbs are better than all the others. If you modify your motor with a bigger cam and so on, a BG Race Demon will outperform Fuel Injection in dyno testing, and the throttle response is insane.

 

hey american thunder, mind doing that equation for a 400m? I am terrible at math and didn't really understand the set up. Plus i don't know the RPM stuff and there info