Probably a difference in gears, but I have a 90 F250 with a 351 that will do 140 kmh downhill with the wind behind it. Has an annoying alarm that kicks in at 120 anyway. As far as the 300, my brother has a 79 F150 that he bought new with a 300. No trouble until around 380k and he put a 351 in......Don't get far from the toolbox now...
Good Luck

 

There must be something wrong with my 300 then because it doesn't have much power from a standstill. I've never driven a 351 but I've driven a 4wd 302 that would stomp my truck. I can't imagine what a 351 would feel like. Hopefully I can find one someday.

 

Most of these trucks had either 3.08s or 3.55s...

All of my stuff had 3.55s.

But looking past the gear ratio...it's a matter of physics....an engine with more horsepower and torque is going to be a more powerful engine than one with less hp/tq...regardless of the truck it's in.

 

what would a high-speed rear end ratio be?? would it make a little better mpg on the highway??

 

Justin, I've heard you say on this forum before that the 351 and the 300 feel very similar until you get to 3000 rpms, and then the 351 keeps on going - why the sudden change of heart?

 

Well, I don't really feel like I've changed my viewpoint on the 300...I might be wording things a little differently or clearly now but facts are facts...

There isn't a lot of difference down low between the two.

We've tested a 300 to the max....including idling it up hills in 4th gear and letting it hug the verge of stalling at about 15-20mph and that son of a %^#$^ wouldn't shut off. My buddies and I have thoroughly tested each of these engines to see what their limits are and what they can/can't do.

When discussing a 300 vs 351 what you say about it depends on what exactly your talking about as to which one is better....

If all we talk about is power output...(ignoring such things as durability)

than the 300 gets the nod in torque down low from idle on up to about 2400 rpm...but not by much. I know my 351 wouldn't idle up hills in 4th like that 300 will. But the 351 makes close to the 300's torque (enough that you can't notice unless you really test them hard) down low. The 302, forget it...not even close.

But...

For example...

You take identical trucks in every aspect, manual tranny, and you put it in 2nd gear at about 5-10 mph (verge of idle) and you give both engines 1/4 throttle...and see which one accelerates faster....the 351 by far. This will also make it feel more powerful than a 300. That is the presence of near equal torque but the 351's nod in horsepower (how quickly work is done) that accelerates the vehicle more quickly.

The funny thing is that I don't feel I'm very biased....as I like the 300, 302, and 351...it's just that they all have their own prefered role and power outputs.

And up until the last....year or so....I havn't had a lot of experience with the 351....

Now I've had the 351 in two different applications with two trannies as well as stock and slightly modified.

Since my 393 has had some trouble the 351 I have is in it's place...with light mods...and with 175k mi on it that thing hauls **** and I love that motor.


There's two things to talk about....horsepower and torque.

The horsepower of the 300 is very low....like a diesel....so it's slow and boring. It accelerates a heavy vehicle like a snail.

In torque...the 300 has gobs of it all down low right in the useable street driven RPM range. Perfect for a work truck or heavy truck that nobody cares about acceleration. It's max tq is at 2000 which makes it have the right tq at highway speeds.

The horsepower of the 351 is higher, making it accelerate the same vehicle much more quickly. As mentioned it will also pull to about 4800 before it really drops off so you have a lot more RPM to work with if you want it.

In torque, it's a little lower than the 300 in torque at the lower RPMs but it makes 50 more ft-lbs overall and that is a big difference. The 351 still has great low end torque but the horsepower to boot....


In the past I've often said that the 300 is the low end tq motor and the 302 has crap for low end tq but it makes decent power up top. The 351 is the middle ground where it has the low end tq of the 300 but the higher end hp of the 302....combined into a package that woops both their butts.