I've got an '86 e350 dually with 460,and am wondering about downsizing the engine when it eventually claps out-hopefully later than sooner!..............What engines will drop directly in to the mounts/tranny,and be the most fuel efficient?
I understand that it's not a major job to change the gear ratio in the diff if necessary-what's the general time and parts budget for that?
Would a fuel injected engine get in thereallright?,or are there a lot of challenging differences?
I DO carry large loads sometimes,but don't mind slowing down on the hillclimbs a bit ..........thanks

 

Why do you want to downsize the engine? It sounds to me like you need a 460 in that truck.

To answer your question: the only smaller engine that will bolt to your transmission would be the 351M/400. They do not bolt up to the mounts, but that's easy to fix.

There's a lot to be said for building a 400, but seriously, if I already had a 460, I sure wouldn't downsize to a 400.

The 351W won't bolt up to anything in your truck.

If you're thinking that smaller engine = better mileage, I'd doubt it in this case. The smaller motor will have to work harder, and would likely use more gas than the 460.

 

Spend your money on a overdrive unit to improve your mileage and keep your power for when you need it. That would be my advice. Your truck is heavy by it's self you need to keep the 460

 

greasymonkey,

I'd keep the 460 and refresh it. You already have the engine, just tune it up if it's tired, or rebuild it if it's really bad. A lot of the time the gas mileage improves quite a bit with some minor engine work and carb tuning.

The thing to keep in mind is that 460 isn't working too hard pushing your van down the road. You go smaller, it'll have to work harder and you'll pay the price at the pump one way or the other.

My suggestion: Give it a good tune up with quality parts. If it's an old carb, consider a rebuild or replacement with a rebuilt unit. Tune the carb up really good, and you're set.

Other options include a camshaft swap for a "mileage" grind, a free-flowing exhaust system (headers, etc), or swapping out the rear-end gears with something of a numerically higher ratio (if you have 4:10, go with 3:55)...unless you are towing a heavy load.

My F350 Crew-cab dually is a beast, and I tow with it. The 4.10 gears make you feel like you can tow a semi! However,I'm getting like 7mpg in town, about 10 on the freeway. I bought a US Gear overdrive unit for it (not installed yet) to try to get the RPMs down. As it's switchable, I can go from 4.10:1 when towing up hills or in-town, and swap to an eqivelant 3.28:1 when running unloaded or up to speed when towing on flat roads. I get the best of both worlds.

Anyways, I'd stick with that 460 and give it a chance to prove itself before downsizing. I think it'll be much cheaper for you in the long run.

 

I agree, dont downsize. "Theres no replacement for displacement". I had a 400m in my F150 that got 8mpg, and I put a 460 in it and I still get 8mpg, but with a lot more POWER !

 

I went up 1mpg going from a 400 2bbl to a 460 4bbl in my 82.

With your truck, I think you would badly regret the day you pulled that 460 for something smaller.

 

........thanks for your consensus,and suggestions!--460 it is!!.................cheers!,,,,,,,,michael.