Engine replacement advice 4.6

johnamcwhirter

New Member
May 20, 2020
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Manassas, VA
Thanks for taking the time to read my post, and in advance for your help.

The situation: I purchased recently a 2000 GT with a seized motor (4.6, 5spd manual - 111k). Previous owner had an oil line plugged and didn't realize it. Sold it to me for next to nothing, so I figured I could use a cheap project. Since the engine is seized, I doubt I would be able to salvage the motor, at least for a considerably less cost than a replacement motor (I have confirmed that it is not something stupid like the A/C pump frozen).

Which brings me to the question at hand: what motor to get. I have already done a good deal of research on this and other forums, so please refrain from posting links to other threads, as 1.) I have already seen them and/or 2.) they contradict other threads that I have seen. Basically, I've seen a lot of confusing/contradictory/incomplete answers to this question.

The essence of my question - I would like to know:
1.) What motors from what vehicles (Grand Marquis, Vics, etc) will be
a.) bolt on
b.) bolt on with a few parts from the old motor
2.) If a given motor will "fit", will I have the same performance as a stock GT motor? I've heard a lot of conflicting opinions on this. Some will say they are the same, some say there are different cams in the mustang motors, different lifters, etc.

Now, on to details about my situation. I am not too constrained by budget, but since I am asking advice on replacing a 20 year old motor instead of buying a new car, obviously I'd prefer to spend less than more haha. The reason I an asking about alternative motors to put in is because I am finding GT motors are consistently twice as expensive as other 4.6s. And I've got plenty of amateur mechanic experience, just never with replacing a 4.6. Or any other mustang motor for that matter.

I'd really prefer first-hand experience. What have you done, what was your experience like, what were the results? Etc. Or at least a well-informed/expert knowledge of the 4.6 motor and its variants. No, I'm not going to go balls-to-the-wall and do a coyote swap lol. And probably won't put a blower on it. Probably not anyway. Maybe. But right now the idea is to get it on the road as close to stock as possible, so I can either sell it or enjoy it for what it is.
 
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tsemmett

Active Member
Jul 2, 2019
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There are really only 2 different variables when it comes to 4.6 longblocks: Romeo or Windsor and PI or NPI. For your purposes, ignore the NPI engines (pre 99 on Mustangs, varies in other vehicles, but 2002+ is generally a safe bet), as they are the older, less performant engine.

That leaves the other variable: Windsor vs Romeo. As longblocks they are compatible, there are just some differences that you ought to be aware of when swapping them, and given that Romeo engines were produced longer and in larger numbers, you're likely to find them. First being the bolt pattern for the flywheel: Windsors have an 8 bolt pattern, while Romeos have a 6 bolt. You have a Windsor engine, and would need a flywheel if you got a Romeo engine from an automatic vehicle. Second thing to consider here is the timing cover. Ford used a lot of different covers through the 4.6's lifespan, and I believe that the Windsor engines are different enough in this respect that you may need to source a Mustang Romeo cover if getting a Romeo longblock (96-98 and 01-04 Mustangs are Romeo).

As for performance, take a look at the interchange on a PI Romeo Cam, and a PI Romeo Head. Notice how many different vehicles use the same part number, yet have different performance characteristics. Those saying that cams differed between 4.6s are mistaken; these applications only differ in intake/exhaust, and in computer tuning; things you will be swapping over anyway. That said, there is a difference in Romeo vs Windsor cams as far as the way the gears are attached (Windsor are pressed on rather than bolted), but the cams run the same specs, and if you're swapping longblocks, this difference doesn't matter.

One performance option to consider here is that there are aluminum block versions of the PI 4.6 2V that would shave some weight off the front of the car. Explorers had them, mostly from 02-04, but I will say that finding low mileage engines from them can be a pain vs other models (I've been looking too).
 
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Adizzle843

Member
Mar 22, 2020
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South Carolina
I bought a 96 GT and began researching the options on the 4.6. The guy I bought it from was at best a shade tree mechanic and I’m surprised it made the drive home. I pulled the motor (motor was going to get built for FI no matter what) and the castings say it came from a 92 crown Vic. Long story short, and some advice from some guys here, I shopped around and found a 4.6 out of a 2003 GT. Paid $300 and even got the bullitt intake with it. The engine is at the machine shop, so I haven’t done the swap yet, but it sounds like a bunch of people have done it, and it doesn’t sound that bad.