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Hey All,

So my 1988 LX 'Vert 5.0 resto project keeps going sideways and sucking up more and more cash. The latest issue is a monster cooling problem. I thought it was just a clogged heater core. Pulled the HVAC box that and the core sure was clogged with rust and everything else under the sun. So, I decided to do the smart thing and overhaul the whole cooling systems. That uncovered massive rust in the cooling veins, a cracked cylinder head, head gasket repair or leak stopper all over the cooling system (actually created pretty a comical cast of the water pump on the timing cover that I had to chip away at), and more. Plus, the one water pump bolt sheered off in the block. Just one big mess.

So, I debated pulling the head and inspecting it, drilling and tapping the sheered bolt, and continuing my plans to flush the cooling system and do a full retso job on it. But I am dealing with a 130,000-mile 5.0 with unknown other issues internally. So, I've decided to go with a reman engine instead.

TL;DR, my 5.0 is a ticking time bomb, so I am debating between a reman 5.0 or a 351W. I am thinking the 351W just for its strength. Sure, it's a convertible, so big power gains aren't in the works, but I plan to tinker a bit.

As much as I'd love to do a 5-speed swap, I need to keep the AOD so my wife can drive the car periodically and to keep it as visually stock as possible. Will that AOD bolt up to the 5.8-liter? Can it handle the extra torque? Will I need some 5.8-liter donor parts to make this all work?

I've done some reading on the forums about the flexplate and such, but nothing concrete.

Anyone have any experience in this?
 

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Keeping it EFI? Youll need a 351 Specific lower intake because of the deck height change.

It all depends on the build. you could have a lazy 351 and the AOD will live for years, or you could have a wild build and kill it quickly. Anything mild, youll be fine.
 
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Stock, a 351 won't really make much more power than a 5.0. They shared the same garbage heads for most of their production, and they do have the same bellhousing pattern, so it mates to the AOD just fine. Now if you happen to bolt up a good set of heads, you will be in a very different situation. The AOD is fine, if you drive like the gas pedal is a porcupine, and you're barefoot. But full throttle shifts into 3rd and 4th put the torque converter lockup in a bind, due to its unique mechanical system. If your engine's making decent power, an AOD produces higher fluid pressures, making the friction materials clamp harder. Unfortunately, the operation of the lockup requires those materials to slip. When they can't, they incur a lot of wear, and put a lot of torque on the lockup shaft. Eventually, either the friction materials fail, or the shaft does. Those defects can be fixed, usually by removing the lockup torque converter feature.
 

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Was thinking some more about this, Cup. There are a few other things to consider about the 351 swap. First, the good bits:

351 (5.8) makes a lot more torque. From off-idle until it runs out of steam, it's just going to deliver more power. For straight line acceleration, it's a big difference compared to the 5.0.

Now the bad.

5.0 is about 80 lbs lighter. Sure, you can put aluminum heads on the 351, but this argument applies to the 5.0 too. All the extra weight of the 351 is up high, due to its taller deck, which will really hurt your handling too, making your car want to lean more in cornering. While the 351 delivers more torque, generally speaking, any hot 5.0 can overwhelm the suspension and tires on a Fox Mustang anyway. A lot of people don't realize that if you take two engines with different displacements and put the same parts on them, they will usually make very close the same peak power. In other words, horsepower will be pretty much identical between a 351W and 302. The 351 will just start making that power a lot earlier. It will also run out of steam sooner, as its breathing becomes hampered by the same size ports that allow the 302 to spin a bit higher. Gearing can make up for the torque deficiency of less cubic inches, which is why 'horsepower' is a better rating for performance than 'torque'.

I am a huge believer in tire smoke being good for the soul, but given that you can get effective performance out of the smaller engine with basically the same parts, my vote is to go with the 5.0. It fits better, is easier to work on in the car, and it handles better.

Instead of getting a remanufactured engine, have you considered getting one out of a Mountaineer/Explorer? Those blocks almost never have significant wear anyway, and the GT40P heads along with the better intake setup are a great power/efficiency upgrade. With better springs and a cam that isn't designed for pulling a plough, there's not much you'd need to do for some go-fast fun. It'd be a lot cheaper, and probably more reliable. I've had really bad experience with buying generic cheap remanufactured engines. Dealt with them twice, and both times, they were absolute garbage despite the big mileage warranties the manufacturer included. Your luck might be better than mine though!
 

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What top end were you thinking for a 351? Let’s say you did a 351 with a GT40 type topend, it would be a dog. Not all that quick and kind of truck like. I think really the only reason to get a 351 would be so you could make a 408 out if it. The bang for buck isn’t there really if you get a 351 and throw the typical 302 top end on it. Typical being something like Trick Flow 170’s.
How about turning your 302 into a 331 or 347? It’d probably make as much or more power than the 351 and it’d be lighter and you wouldn’t need any “swap parts.” As far as strength goes a 500 horse Fox build is kinda spendy and a 400 horse Fox isn’t exactly slouch.
Your stock aod won’t even handle 300 horses very well. You’re gonna want to beef it up even if you just did a 302/306 and a new top end.
 
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