First off, I'm looking for a 3/4 pickup engine. Revving past 3000 won't happen and I'm not trying to win a race. I am trying to save a little money and maybe get a good little engine along with it.

The 400 that I have now is in my 79 f250 crew with an nv4500 behind it. I believe the engine has 360,000 on it. With my light foot, the od trans, and 3.54 gears I get on average 10.5 mpg. Engine has a weiand intake and a 650 cfm 4 pot edelbrock.

Really the only problem is this thing can't pull anything over 4000 pounds. It's ok when going around town, but I put a trailer and it gets pretty under powered.

I'm looking to make 200 hp under 3000 rpm and 350 pounds of torque around 2000. Like I said before building this to rev past 4 grand is useless for me. I'm just going to do some towing (15,000 gcwr) and want it to be able to get out of its own way.
The next goal and probably the hardest one is I want to get around 14-15 mpg. I also want the engine to be reliable. I don't want to have to rebuild it every 100,000 miles.
Is what I'm looking for feasible? Would I need new heads or would my originals do with some work? I know a valve train, cam, headers, and pistons are needed. I'm looking to run 87 octane. Maybe 85 if it would help, there's a couple places around here that sell it.

What do you guys think I should do? Any certain combustion ratio or cam you guys would recommend? Thank you for your help in advance. I'm going to be assembling the majority of the engine myself.

 

As much as a 400 build is imo the better route in most cases, if you want low rev, cheap gas (and lots of it) pulling power, just do a 460 swap.

 

Any decently-built 400 can do what you are asking. Here's what I've seen with the 400's little brother, the 351M.

I have two trucks with 351M's - Rusty and Dad's truck, both 4x4's. Dad's had a stock 351M and performed poorly. Step on the throttle and little happened. And with its C6 transmission and 3.50 gears it got 10.25 MPG. Rusty, however, had a built 351M. Nothing fancy but it has an RV cam and an Edelbrock intake and 4bbl with stock heads and exhaust. With the non-OD NP435 trans and 3.50 gears it got 13 MPG and would pull anything - including a 1950 Chevy pickup on a car-hauler trailer. I got the bright idea of making the best of both worlds so put the built M in Dad's as well as a ZF5 tranny - and got 15 MPG.

Unfortunately the 351M can't really be helped much as there aren't good pistons for them. But Tim Meyer has good pistons for the 400, and can Sell you the right cam as well. With a good compression ratio, a good carb, and the right cam you should easily be able to get 15 MPG at 60 - 65 MPH, assuming your axle ratio is around 3.50.

 

Good deal, I won't be building probably until this winter. Thanks for your help. Any recommendations?

 

Would it still be cheaper after I have to find a 460, get a clutch for it setup, get new accessories for it, new mounts, and then start building it? Head work is gonna cost the same, I'm not doing anything crazy. New Pistons, cam, rebuild kit is gonna be close to the same cost, I'm not looking for any parts for the 400 that have to be custom made, everything I want is available.

Would a 460 be able to get the 15 mpg in looking for? Would I have to swap front springs for the extra 200 pounds?

 

My recommendation is to contact Tim Meyer. He is the only one with good pistons for the 400. Tell him what you want to do and he can sell you pistons and cam, and you can have the machine work done locally. Or, send the engine to Tim and have him rebuild it.

 

Would TM be able to spec me out a definite cam to do what I want to do? What I'm trying to say is I don't want to get a cam made and it not be what I'm looking for. I want to get everything it if it I can, don't want anything left on the table if I'd have just went a couple degrees either way on the grinds. Would he be able to get me what I'm looking for? I'm going to do as much work myself, everything else will be taken to a machine shop I'm good with.

 

Well, he's the #1 guy in the world on these engines. Builds many of them each year, and runs many of those on his dyno to see how they perform. If he can't, no one can.

Tim has his own custom cam specs that he has Comp grind for him, depending on what the customer wants. But, if you just call Comp or any other cam company all they will sell you is one of their off-the-shelf grinds.

 

Bump up the compression, custom roller cam and Pistons from Tim Meyer will get ya there. The MPG is gonna be tough. Fuel injection. One of the four barrel self tuning systems from MSD, edelbrock or FiTech. A 400 will make peak torque lower than a 460

 

DirtyLarry,

Okay... Here's my opinion on your prospective build.

It's going to be difficult to get so little power out of a 400. I think it was Classic Trucks did a "stock" 400 rebuild and got something like 265HP and 415 lbs./ft. torque. I don't remember the details, but it was a 2bbl. for sure and most likely had a straight-up timing chain - I've heard that alone is a noticeable improvement. Since they were around 183HP in stock DOG form from Ford at the height of the "gas crisis" of the 1970's you can do just about anything and exceed 200HP with ease.

Your only real challenge is the mileage. You might consider a gear change, and even swap the Holley 4bbl. out for a small Holley 2bbl.

You don't need new heads, a roller cam, or anything exotic, but pistons from TMeyer are an excellent upgrade.