I have started my 390 build by taking the truck off the road and pulling my front diff as well as the motor.(need to replace a bearing in housing)
A mechanically inclined fellow I know who has a good rep as a handy man to have around is trying to convince me to drop a 460 in the truck instead.
You see he has one that is in good running order with a 4spd tranny out of a 76. The truck kinda gave up the ghost to rust. He wants to do the swap and make it all good to go ...AND.... give me the motor for nothing, as long as I haul the old body to the wrecking yard.
He has done a few i-6's over to v-8's and knows what to do, he's an old Ford man. He is also convinced that the 460 set up right with a 4bbl(which it has) and a better cam along with timing gears from a 429 and headers, will out pull and get better mileage than a 390 with the build I want to do.
I have know idea if I should do it or not. I only know 460's can be real 'tuggers' if you get the right one, but pathetic on fuel. I hate free opportunities.

Any comments??

 

When a 460 carburated motor gets better gas mileage than a 390 is when we will see 25 cent a gallon gas again, it won't get worse either. Will it out preform the 390, yes. BTW all 460s came with a 4 barrel carb and they are all junk and need to be replaced. Oh yeah, at this time I have a '68 F250 Camper Special with a 390 4 barrel and C6 and an '84 F250 Supercab, Superduty with 460 4 barrel and C6, so I have compared.

 

So if I invested the money originally budgeted for the 390, into the 460 instead are you thinking it might be a better choice? I will be driving empty alot but do have to haul extremely heavy loads occasionally. It will be highway pulling and gravel roads in gas fields. In other words hauling equipment and materials on long huals.
See the idea is sorta appealling because I don't have to do any of the wsork as far as rhe change over goes.
I just don't know.

 

I was thinking about doing that same swap when I did my rebuild. Cost wise it depends on what you want to do. I was looking at a mild compression forged piston and ring set, edelbrock alum heads, rpm intake, crane cam, Holley 750, all MSD ignition. Cost was about the same over all for those things. Heads are more for 460 but 390 intake is more then 460 intake. Cams about the same either way. Carb is the same. Dizzy pretty hard to base a decision like this on a dizzy. Machine work plays a minor role also. How much machining does either engine need? I went with the 390 build. Mainly because I didn't want to pay the extra cost of the motor mounts, headers and other stuf needed just for the swap. I spent alot of money (for me anyway) to get the 390 to where it is. The same money in a 460 would have me running circles around this 390. Anyone can put a 460 under their hood and make it go fast. It's unique to do it to a 390. I always have someone come up and ask "Is that a 460?" I love the look on their face when I tell them it's a 390. Just my $.02

My vote is for the 390

 

Oh boy here we go again!

I'm going to vote 390 as well. When you go 460, you add 100+ lbs to your front end. I added the + on there, since you can and probably will end up putting an aluminum intake on that 390, which will reduce it's weight about 50lbs. So the 460's more like 150lbs more by the time you're done.

I really dont think it'd cost any more to go with the 390 than the 460. You just have to know what to spend money on, and what not. If you're smart you can get the same power for the same money. The 390 will just have it a little higher in the RPM band.

The 390 should get better fuel economy, depending on how you build it of course. They'll both be gas hogs, but the 390 will just be a little less of one.

 

Made both 390s, 427s and 428s go very fast. Have also made 390s and 428s get respectable gas milage and pulling power. Done the same with 460s too. The statement "Anyone can put a 460 under their hood and make it go fast. It's unique to do it to a 390. It's unique to do it to a 390. " is BS. A good running 390 was the norm years ago and is IMHO the same today. I've seen guys screw up a good engine rebuild by putting the wrong intake system on it. Stock truck 460's will out torque a stock 390's, but the 460 isn't happy above 4500 rpms any more than a stock truck 390 is. Unless you swap the cam in the 460 stay with a 600 cfm just like you would with a 390.

 

Never thought of the weight issue and wasn't planning on beefing up the front suspension. My build is really close to yours Rusty and what you have relayed to me in the past sounds like it will pull all I need to pull. The 460 was just a left field suggestion and I only had my old man's 76 f-150 2wd to refer to for power. That was also a long time ago so I don't remember.
Like hatemakings/n said it is unique to run a 390 and get loads of power. Even with it all stock it goes good just not what I want and need.
There is less headaches I'm sure to stay 390. After all that is what the '71 was made with!!

 

I suppose it depends on your intended use of the truck. The 460 has a better torque curve for low end power. thats why the ski boat guys use them. using stock heads, manifolds, cam the 460 will outpull any 390 in same dress!

 

I don't by the 100 lbs difference. The difference in weight between a 390 and 460 are not enough to worry about you for your front suspension. The 390 has a full skirted block and the 460 does not. All that iron in the skit pretty much evens out the weight issue. As to pulling, my RV cammed (I don't remember the exact spec but it was around 240 or 260 duration with lotsa lift) 390 with dual exhaust and a 600 Holley 4 barrel will out pull any stock 460 with the same gears, I know this cause my racing teammate had a 460 truck he towed with to the races. But stock, no contest. If you build the 460 like you were gonna do the 390, then the 460 will out do you 390 and still get you the same gas mileage. My 390 got about 10 to 12 mpg while my 460 gets 7.5 to 10 but it as 4:11 rear gears where the 390 had 3.73s.

 

7-10 out of a 460 ain't too bad. My 390 gets 10-12 with 4.10 gears but I have 35" tires so it probably compensates up to 3.73s.

 

I have a overdrive NV4500 manual trans in my 68 f-250 4x4 with 460 tri-y headers 600 cfm carb, gets 15-16 open hwy

 

Ok. Look at this. It's only 95lbs difference.

 

Yeah, my buddies 460 had 3.73s that we compared the 390 to and his mileage was close enough to mine that the difference was driver style.

The 7-10 mpg is going up next month when the Holley 1850 600 CFM, massaged by me to pretty much the same spec.s as my 390 carb goes on. Gotta do the vacation thing first. I also have a double cold air feed to the air cleaner ready to go too.

 

2 questions. Is your truck a 4speed or an automatic? Second, is the 76 a highboy? If the answer is yes to both questions then go with the 460 swap. You can take the front springs and any other parts needed from the 76 to complete your swap. If the 76 is a highboy then the frames are the same on both trucks. You will need the perches from the 76 for the 460. There are a lot of parts that you could use on your truck from the 76. hope this helps.

 

I would never have believed it. There must be a lot of meat in the heads.