I have a 1981 F250 Ranger 4x4. It came with a 5.8L 351 Modified. My intent was to rebuild the existing engine, and convert it to the 6.6L 400. Upon disassembling the engine, I found out the heads were shot, and one cylinder wore off center, so the block was shot. In addition, the block was already bored to .030 over, so it was already rebuilt at least once. Now I'm all for keeping things pretty factory and original, but I would like some input on whether to replace this engine with another 351m/400, or should I opt for a 460? I know and the 460 was dropped for the 1980 model year and returned in '83, and from what i've read, the 400 was heavily restricted by emissions and couldnt fill the big shoes left by the 460. If i'm not mistaken, the 460 shares its bell housing with the 351m/400, so use of the existing Borg Warner T-18 tranny shouldnt be an issue right? and would axle ratios come into play? I plan to ultimately restore the truck and work with it (snow plowing being a big part of it). That being said, what is your opinion on the matter? and the pros and cons of each?

 

They do share bell housing pattern for just that reason, so they can share the same tranny's as Ford was evolving their big engine line.

The down side would be all the different things you would have to change (motor and frame mounts, exhaust, radiator hoses, etc...)

Pro would be the 460 would probably be a better performer all around. Not that the 351/400 was a bad motor, I just think in stock trim, the 460 was a gutsier motor.

None of them get mileage worth a damn.

 

I got the truck out of a field just over a year ago. The Old engine did run, but obviously not that well. The Exhaust is in need of replacement anyway, and the radiator hoses and radiator are shot also. Alot needs to be replaced either way, thats why I'm considering the switch

 

I like my mildly-built 400 just fine.

None of these engines are good candidates for keeping stock, though, they all suffer from low compression and retarded timing out of the factory.

 

I did have a 400M in my 78 F250. Great truck motor. No top end to it, won't win any races. But was a great motor and never, ever had any problems with it. I think the entire time I had it all I did was change the oil in it.

 

Mine rarely gets much over 3,000 RPM, it's seen 4,000 only a handful of times.

Great low-end torque, though; I bought it for hauling firewood from the mountains down to my house.

 

This brings up a good question JMyers...part of your answer has to include what exactly you want to do with the truck.

If you want it solely for just that, hauling and being a truck. I'm not sure it would be worth the hastle of swapping to a different motor. The 400M will do a great job of that.

If you're wanting to hop it up a bit....maybe the 460 is a better option. And I say that only because I'm not sure of the performance capability on the top end of a 400.

But a good running 400 you would be pleased with I think...if it's truckin' you're wantin'

 

Look in the sticky of the 335 forum, I think there are people/magazines in there who have built high-RPM variants of the 400 but it takes some doing IIRC.

IMHO the 400 is the V8 equivalent of the 6-banger - a great, low-end-torque truck engine, not a high-RPM race car engine.

 

Mainly the "truck" aspect of it. Snow Plowing, Hauling, Towing, etc. All the stuff trucks are made to do.

 

Keep in mind that with a 460, you'll have to cut anywhere from 2 to 6 rivets just to remove the 351M/400 engine perches. You'll then either have to buy some really expensive aftermarket L&L 460 motor mounts, or spend more time cutting 2 to 6 rivets from the perches on a 460 truck so that you can use 460 motor mounts.

Not only that, factory 83+ 460 trucks had the cross-member notched to clear the front oil filter. They also used a special adapter that moved the oil filter from facing sideways to facing the front of the truck. You will either need to grab a factory adapter and hope your cross-member doesn't cause any issues, rig up your current cross member like a redneck, or run a remote oil filter.

And if your springs are as tired as mine, the extra weight from the 460, although minimal, can make a difference in your front ride height, and possibly your camber as well.

Personally, I would stick with a 400M. As long as you don't plan to race your truck, or rev past 4K, you'll be fine.

 

Forgot about the cross member issue. My 82 has all of that. Looks stock so you forget it had to be done.

 

I believe the determining factor will be availability. The 351m/400 is a older style engine discontinued back in the early 80's, while the 429/460 was around into the mid 90's. Although a factory 460 EFI can't be readily swapped to a carb without changing the heads, there still may be more of them around.

So if you have a lot of 351m/400 engines available to you cheap, that may sway your decision. You might also want to look at engine kits and such, and see if there is a major difference in the cost of each engine.

You also may find a later model complete truck with a 460 and a 5 speed. I would jump on something like this, and swap the 5 speed in also to get the overdrive.

 

I'd have to agree. I've talked to people out far west and in Canada who tell me they can't visit Craigslist/Ebay/Kijiji or a junkyard without finding at least six 351M/400's.

Here in Florida, I find 460's all day long, but have yet to see but two 351M/400's.

 

If you elect to do the 460 swap,you can buy swap motor mounts that will keep the trans in the original location and allow you to keep the tower mounts.I used a set on an '88 f250 for a 302 to 460 swap and they fit fine.Bronco Graveyard and L&L Products sell them for ~ 125.00.The 460 will have more torque.As was suggested earlier,you might want to see wether 335 or 385 series are more common in your area.