Motor swap options
 

This is my first post on FTE, so pardon any inaccuracies. I'll start with some background on the truck. I have slowly, but surely been rebuilding a 1978 F150 Ranger XLT since just after Christmas of 2015. It has a 400 and a c6 It went through it's service as my daily throughout highschool, it's repairs on the side if the road, and just all around being pieced together. In September of 2017 another truck got T-boned in front of me and hit the front end of my truck. In all reality the damge wasn't bad, especially compared to the other vehicles in the accident, it did however require a new passengers fender and grille shell. In December of 2017 I bought a new daily, and started tearing the truck down. I knew there had been rust in the cab, it was a plow truck for decades before I got ahold of it, but I assumed I could just patch the floors. So while I had the front end apart, I also tore out the interior to fix that while it was down. Upon tearing up the carpet up I found a much larger issue than I orgiorigin thought I had. The only floor solid in the truck was around the transmission tunnel and around the seat mounts. At this point I began searching for a new cab. In January I found a good deal on a 76 F100 cab. Over the course of 2018 I slowly tore the rest of the old body off and set the new cab and fenders on. It's slow process between college and work on other vehicles. Recently I needed to put cab corners in my girlfriend's 1993 F250 extended cab, this required me to move my truck to the opposite bay of the garage as there's only one plug for my welder in the garage. I fired up the pieced together dentside and decided to take it for a drive up the driveway. I made it about halfway to my aunt and uncle's up the rest of the drive, and then I start hearing something I dreaded hearing since the day I got the truck. I've always heard that the 351m/400 are unreliable motors that are guaranteed to break, and now it seems mine has. I started to hear a knock in the number 7 cylinder.

Now here is the reason for making this post. I'm at the point where the truck is gonna need the motor replaced. I am planning to pull the entire body back off the truck and send it to be body worked and painted, that leaves me with just a frame to place a motor and transmission in. I have a few options I'm throwing around and looking for some insight on the specs of each option. Each option will include swapping a manual in place of the c6, I have the pedal assembly and other required parts for an era manual swap. In the end I would like to have a reliable truck, with not horrible gas milage, that will see some heavy towing and light offroading, and of course it has to sound good.

#1- what I believe to be the simplest as far as fabrication, but remains my least favorite option. Rebuild and upgrade the 400 that's currently in the the truck, and swap the c6 for a NP435. Issues I see with this plan, I have little experience rebuilding engines besides single cylinder Briggs and Stratton motors, I don't have a bell housing to mount my NP435 to the 400, and I worry about running into the same issues that have plagued the truck up until now. The truck tows horrible, gets single digits mpgs, and has never been overly reliable. I don't mind tuning and repairs when needed, but not knowing of it was going to start when I turned the key is not what I want to continue to have

#2- one of my favorite engines of all time is the Ford 300 I6, and makes this one of my top choices. Pros of this plan is they are one of the most reliable engines of all time, and can be extremely good at towing and offroading, they also get decent gas milage, and were available in these trucks making the swap fairly easy. I also have two carbureted I6s available fairly cheaply from my grandfather, and the NP435 I currently have will bolt directly to the engine, I also have family members that know much about these engines to aid in the install and rebuilding. Cons I see with this plan is that the engine would need a rebuild, and I would need to buy some performance parts to get the engine where I want it, such as a 240 head to up compression, cam and valvetrain, a 4 barrel intake, and headers. It also does not have the sound of an old V8

#3- swap in a 302 or 351W small block. This has the same perks as the 300 as far as ease of swapping, availability for me to mount my NP435, and are both fairly reliable. I also have a carbureted 351 and 302(which would not require a rebuild), as well as two fuel injected 302s to pick from. Cons I see are that neither make an overly smooth torque curve, the 302 is not a very good towing set up, and neither will do great on milage. Some of the options also need rebuilt and swapped to carburetors

#4- is definitely the most ambitious of my options, but also remains one of my dream builds, and I have the perfect time and ability to do it right now. My dream build for a dentside has always been to swap a diesel into it, I've gone back and forth forever on what motor to pick. I've gone from a small I4, to the 7.3 powerstroke, and the 7.3idi, yet I always seem to land on that last option. I would love to put a 7.3idi into this 1978 that I have right now. My grandpa has a 1991 F350 dually with a 7.3idi and a zf5, that would be the perfect donor for this truck. My plan would be to modify the frame to accept the the motor by installing the crossmember out of the 91 into the 78 frame rails. I would also plan to replace the coil springs in my F150 with the coils from the front axle of the F350 to support the weight. I would also plan to swap the hubs out for srw hubs and out the Sterling 10.25 in my F150 as well as swap the front Dana 44 to 8 lug. I could swap the rear spings to the F350 springs, although it also has F250 springs now. I would need to buy a T19 bell housing to mount my NP435, along with a new fuel tank in place of the original metal one. It would also need the hydroboost system installed from the 91.

Some other notes include I would like to buy an overdrive unit for use with the NP435 to give myself better gas milage, but I am unsure if I would use a splitter before the trans or a electric unit after the transfer case. I also want to swap the NP208 currently on the NP435 to the NP205 on my c6. If anyone has any insight for me on these options, it would be greatly appreciated. Thanks
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Welcome to the forum. How long have you been writing novels?

Rebuilding that 400 could be easy and fun. Or it could be a pain in the ass depending on what kinda shape it's in. The most important thing I've learned is that it always costs much more than I thought it would to rebuild. Buying a reman short or long block usually works out a little cheaper and easier. But it sure is fun rebuilding one. Google, forums, and YouTube are most useful here. One of the big expenses is tooling. Getting tooled up to remove/install, assemble/disassemble, is pricey. That said, I'd lean toward having the block cleaned, inspected, and machined. Then do the work myself.

To swap in a NP435, T18, or T19, you're gonna need some stuff that can be tough to locate or fabricate. Brake/clutch pedal assembly, Z bar with bracket, pushrod, clutch fork, etc. Bell housings are fairly easy to find.

As for towing, you can build and gear to handle that. Do the math on your camshaft, compression ratio, and gearing so you know exactly what you're getting. I've got a 400 built for low-mid rpm torque, T18, and 3.50 gears. The drive train is capable of towing much more than the rest of the truck can control. Specifically, I mean poor brakes, frame flex, and light overall vehicle weight. In stock configuration, these old trucks don't handle a heavy trailer well enough for me. I pull a M101 trailer I set up for welding fairly often. It handles ok. But when I hook up to the heavy 18' trailer with a 1500 lb mower, or a couple of pallets of seed, fertilizer, or corn (4000 lb) it gets pretty squirrely braking in curves. These are things to consider seriously. Especially if you're thinking of a diesel swap.

The 400 when rebuilt properly will out power and out tow the other gas engines. Gas mileage will still not be great but low to mid double digits is achievable with a good tune. See Tim Meyer (tmeyerinc) for parts. The 300 and 302 would get decent mileage but not tow very well. If I was going to swap in a diesel it would be a turbo for sure. A Cummins 6bt is the easiest and very reliable.

me, I'd stick with the 400. Mine makes about 360hp/450 tq and i get 12mpg city, 15 hwy

As far as the manual swap is concerned, would pieces from a small block be usable? I have a clutch/brake pedal assembly from one of my dad's old trucks, so that's not an issue. I have a 1986 F150 with an efi 302 that I would be using the NP435 from, would the other parts also be usable in this truck?

Do you have any modifications done to the brakes, frame, or suspension on your truck, in order to help with the issues for towing?
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How much money is lipstick on a pig worth ?

Everyone replaces these engines with a 385 series engine for good reason. it's the best and most economical option by far if you plan on keeping the rig.

Pedal assembly is a biggy. Good thing you have that already. But Windsor's and your 400 use different bellhousings, and clutch linkage. I don't know about the Z bar interchangeability. The toughy is the 400 / 351M clutch fork. I've never seen any reproductions or NOS. Somebody here can probably source one for you. I have occasionally seen old forks on ebay though. I bought one for a spare.

Not an LS. Not an LS. Not an LS...

If you're not wanting to go to a big block, my votes are for the 300 or a 302/351W.
The 300 is a good engine, and probably won't need to be rebuilt, and with just an intake and carb swap, will probably outrun a stock 140 HP 302. I like the smooth sound from the log exhaust manifold, so I wouldn't do headers or the EFI split manifolds either. They make the engine sound too choppy and V6-ish, but that's just me.

A 351W or even 302 will be a good engine if built for torque. There is a ton of aftermarket support for the Small Block Ford. Get some good cheap Explorer GT40 heads, and add an aftermarket RV cam, (roller conversion if possible) good valve springs, and a dual plane intake manifold, and you will have a real decent engine. Only problem with them is headers, because of the clutch linkage.