83' I6/4sp w/od


I have an 83 with a rebuilt engine that I am thinking of building but I'm not sure its worth it if the engine-tranny combo can't handle todays highway speeds since I would like to use it to travel and vacation in. Is 80-85 miles per hr possible without over taxing the engine?

 

LOL! If you want to go that fast you should get something that isn't a brick on wheels. You'd waste too much money building the engine to attain those speeds constantly, then there's the issue of getting single digit mpg. If neither of those things bother you then by all means go for it.

 

You drive a Bronco with a 300 6 @ 80-85 for extended periods it wont last long. It is not made for that.

 

80-85 is getting up there, even in a semi-powerful car. Definitely not the most ideal scenario for a Bronco with a 300, especially if the rest of the truck is old and worn out. I mean, the 300 was in enough vehicles, I know of one in a work van that regularly traveled the interstate at 70+mph, as well as a lot of stop start commute. It was well over 200k miles, still didn't burn oil. It achieved about 15-16 MPG average.. but then again it wasn't a 4x4 and such. They are good engines though..

 

with a ZF 5 speed, proper gearing and stock tires I think it would be fine. the motor wont last running 3K rpms all day though. 2200rpms at that speed would be ideal. just don't expect it to pass easily due to lack of HP.

 

Is there another driveline configuration that would get me there, I live in Houston but like the mountains and driving 70 mph on a Montana highway will only get me run-over.

 

If you are really into high speed in a Bronco you might want to swap a 460 into it. Its gonna get about 6 mpg runnin 80 though. Maybe

 

I have a 500 hp 460 bronco. It has a C6, 3.55s, 35 inch tires, and a 3 inch lift. If you do a 460 swap, you will need to do a ZF5 as well. I don't have a tach, but at 85 mph it is screaming! I get 6 mpg around town, never did a long highway trip. Don't lift it! going 85 mph in a lifted bronco is very scary!

 

Wait, maybe I should explain a little more. My DD is a 14' F150 scab w/5.0. It will do 85 mph all day long effortlessly. But I do like a Bronco and I would like to start doing some traveling, camping and hiking etc... out in the wilderness where my F150 won't go so I thought of the Bronco. So can I get 75mph out of one, maybe a 93' to 95' w/302?

 

My 91 f150 with a 5 speed and 302 could do 75 mph all day before I sold it.

 

run a ZF 5 speed 3.55 gears and 31" tires and you should be able to run 75 on hwy.

 

I have an '81 with a 300 I6, NP435, 31" tires and I can fly at 80 all day long.
It's around 2600 RPMs. Overdrive is going to drop that considerably. If I still had my overdrive SROD, I'd be around 1900 which is plenty easy going. The 300 is very smooth and durable and should do just fine if it's in good shape.
My last trip I got around 14mpg @ 80.

Just be sure your tires are speed rated for it, you have fresh fluids in your differentials, fresh trans fluid, a fresh coolant system, fresh oil, etc. Be sure your brakes are in top shape and your suspension is too.

However, the issue you may run into is power. The stock 300 just doesn't flow very well. It has a restrictive exhaust, intake, and head from the factory. So even if it'll do 80 in the flats (I've done 90 before back when my Bronco was stock), as soon as you see any kind of a grade, your speed is going to drop like a rock. It just doesn't have a lot of oomph.

A better exhaust (grab some exhaust manifolds from an EFI 300 and put on a 2.5" exhaust), a carb upgrade, some head work, whatever you're budget/mood allows, and it won't be any problem. The 300 wakes up easily.

But, to reiterate, just be sure your suspension and steering are top notch. At those speeds, your engine/trans is the least of your worries.

 

Thanks to all of you I let you know how this turns out.