Gentlemen & lady wrenchers, I am seeking your advice on an 05 XLT F150 3V 5.4L 266kmi motor and Trans 4x4 with 390 ratio.
I purchased it knowing the engine was rough on its last compressions, having the idea of putting in an 800hp 351 and a C4 Trans. I talked with mechanics,
2 engine builders, and 1 engine refurbishing company that refused to even sell a short block 351.
Everyones I spoke with gave the same speel 5.4l 3V out and 5.4l 3V back in.
I've been told the 351 won't bolt into an 05, that the frame would need modification, and it the 351 I'd never get operational. So I've decided to ask this forum to see your concensus about all this.
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Let me say this, in my opinion this 5.4 3V engine is the nearest waste of resources Ford ever produced.
I drove the truck about 45mi b4 it blew up, cam phasers rattling and all. Thanks for your time, I look forward to hearing from all, good, bad, just indifferent.
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So you want 800HP from a 351 block? Two things come to mind. You'll need a LOT of money. Reliability and 351 engine at 800HP can't be said in the same sentence. Reliability of a 351 block drops like a rock once past 400HP. Sure, it can be done but why build a future problem child? I would suggest looking for an EFI 460 engine out of a 90's F150, preferably transmission and all including the PCM. Then all you have to worry about is mounting it in the frame which is pretty much a no brainer by comparison. Remember, you're putting this in a heavy truck, not a Mustang. If you're wanting the HP, it's far cheaper to go big block and then you have the meat to get all the power you can afford. The 351 is probably the second worst engine to ever sit in a truck. You already have the worst engine, the 5.4. The 351 is not much of a step up. I vote big block.
A 600HP 347 cu in

 

The 351W has a 4" diameter on the main bearings as I remember, much larger than other engines. this means the speed of the two surfaces moving against each other is too much for a high rpm engine. A 351 cleveland is a better hipo engine. But what you are talking about doing is VERY expensive and it won't be street legal if that matters. The shops would be doing something illegal federally if not in your state and they would open themselves up for huge penalties if they convert your truck to a non-legal vehicle.

 

Easiest way to get this thing back on the road reliably is a reman 5.4 3 valve with phaser lockouts and an appropriate tune. If you are looking for more power, look at a 6.2 and 6R80 conversion.

By the way, there's no way a C4 can handle 800 hp, regardless of what engine it's connected to.

 

So the original engine went 266,000 miles and you think that is the worst engine ever? I've had many vehicles that had engines that didn't last half that long.

 

I think 266K out of a small V8 is good.

If you throw some quick maths at it... say the truck got drove 40 mph for the duration of those 266k miles... that means the engine has 6,650 hours on it.

Most gasoline variants have a built-in MTBF of ~5,000 hours before rebuild -- IF regular maintenance is applied. Anything after that is considered a bonus.

It ain't no heavy duty diesel truck industrial engine that designed for insane amount of hours...

My humble opinion: Repower it and throw a rebuilt 5.4l engine in it with a Melling oil pump. While you are at it, get the transmission redone too.

 

There are people that are doing modern 5.0 V8 (Coyote) swaps, there's companies that are building harnesses to make it virtually plug and play now

I hope you got the truck for cheap enough, and the suspension and front end have been rebuilt at least once in its lifetime