Very long story so skip to the last paragraph if you want the question/advice!

So quick background, I bought a 1978 F150 as a project right at the start of COVID thinking I would have time off to work on it. Well I am in the military and got a total of about a week off so that went out the window and the truck has sat covered since then in my yard. Well I finally got 100 other projects done and decided to dig into the f150.

I bought the truck initially to LS swap it. I know, I know. Well I found a donor truck that had been in a minor accident but the owner was selling it cheap because according to him “bent some suspension stuff”. I had it towed home and after getting under the truck all that broke or bent was the sway bar end link and the drivers side tire Rod (he drove it home and the tire Rod broke when he backed it in his driveway). Well literally $16 from rockauto and $100 for a drivers door and fender that are the perfect match and the truck is 100% running and I am actually using it as a spare truck when the kids need it.

I started think I would just get the ford running with the motor that is in it (supposedly a 400) with a c6 trans and the transfer case. I also have the original manual transmission and transfer that was in the car before and a second motor that is supposedly a 351M. I never looked at the motor in the truck over the 3 years because I never intended to use it and selling it seems like I would only get a few hundred dollars. So before I tried to start it, I decided to turn it over by hand on the crank bolt. It turned but only would got 90 degrees either way before it would stop on something that felt like metal to metal contact. Well I pulled the valve covers and the far rear passenger side intake push rod was bent pretty bad. Ended up pulling the intake and heads today and this gets me to the point of the questions.

the cylinder that had the bent push rod had some rust in it where it looked like water was in it, looked around the cylinder and there is a good sized crack/hole in the side of the cylinder wall where my guess it it cracked when someone tried to start it with water in the cylinder so the block is scrap (the piston tops had .040 on them whatever that means). Now I still have the other complete engine and the heads that I took off look fine but I have no idea what is in either motor parts wise (the spare motor looks bone stock like it’s never been apart). I haven’t taken that motor apart yet, that’s a project for another weekend.

so here are my questions/options:

Options 1-3 also include having to buy a new ignition module, new distributor (wires on the truck are really nice), building an entire exhaust and refreshing the c6 and checking the transfer case because who the heck knows what condition they are in. Probably also have to get new driveshafts unless the manual trans are the same size as the c6 setup.

Option 1: Assuming that between the two motors I have enough good parts to either do a quick driveway refresh to get the motor running, I assume all I would need to do is take them apart, check for any obvious issues and for the price of a new gasket set I COULD be up and running or I could be pulling the engine apart again because bad cam bearing, bad main bearings or excessive blow by from worn rings. Is this worth it to try?

Option 2: If I take the other motor apart and the main parts look ok I can take them to a local machine shop to have it clear, checked for cracks etc and have new bearings and piston rings in at a minimum, if the cylinders need bored or the heads need decked, I would have those costs as well. I am guessing $2-300 for the machine work, potentially $400 for new pistons and a gasket set. Maybe $1000-1500 for a refresh but still a stock motor.

Option 3: same as option 2 but put a bigger cam, raise the compression a little with either deck work or pistons and other wise the same stuff as option 2. A total cost of probably $2000-2500 or $1000 more than option 2

Option 4: LS swap it. Not my first swap so I can do all the work. The problem with this option is I have that other truck fully functional and I have to waste that now so I would probably look for another truck. Buying another truck with engine, trans and transfer case will probably be around $1500 or so. I could probably do the remainder of the work for about $1000 because I would want to freshen the motor, put a nice cam in it etc. cost here would be $1000 if I use the truck I bought initially as the donor engine up to $2500 if I find another.

Option 5: sell the rolling chassis as is and just do something else. Sort of took the wind out of my sails when I found the hole in the motor and have to do a full rebuild. Not sure what I could get for it, frame is in great shape, previous owner put in new floor pan (didn’t do the best job), cab corners are good, truck has a lift, front disc brakes and looks pretty cool even in 4-5 colors because of the flare side bed.

I know that’s a novel and I know I am asking on a ford forum where everyone is going to default to the non swap but was hoping to at least get a cost sanity check, I just want to get it running for as little as possible to enjoy it and tinker around.

 

I think your answer lies ..... Until you dig in, you don't really know. 400s and 351Ms share everything except crankshaft and pistons. Same bore, but the wrist pin location is different due to the 400's longer stroke. It's a truck, not a race car. You are the best judge of available resources.

Good luck.

 

thanks, are the prices guesses for the 351/400 work and parts close?

 

Well, where do we start? Your preferred Gen 3 or 4 SBC swap isn't going to be cheap unless you want to use some clap trap, worn out engine and transmission, and it's also going to require a lot of labor which means downtime on the truck. Then, when that engine and/or transmission inevitably craps out you're back here again asking what you should do. What is the RPO of the engine you want to use? Model year? Depending on that, the wiring harness and controllers are going to be varying degrees of "pain in the ***-ness" and cost you either time or money, possibly both. Save the modern engine swap for something that's more of a high dollar project.

I'm guessing you're partially considering the SBC swap due to your previous comments about fuel economy. You mentioned in the other LS swap thread that 20MPG is what you'd expect. Not gonna happen brother. Forget about this fuel economy nonsense. You're going to be driving a 4000+ pound truck that has a coefficient of drag that's not much better than a rectangle. 0.65 is probably a reasonable number which is essentially horrendous for fuel economy. It doesn't matter how modern of an engine you put in the truck. Physics don't care. That truck is simply going to have an incredibly high road load torque value. BSFC is determined by road load. Yeah, modern EFI engines are going to be more efficient to some degree, but there's a stopping point and it ain't 80% above what an old tech carb'ed engine will do. You MIGHT gain 2MPG, but WHO CARES? I simply do not understand all of the fuel economy threads on this forum. You're driving a 50 year old truck that was designed at a time where no one, and I mean no one cared about fuel economy if they were driving a full sized truck. These trucks were essentially draft horses and much like draft horses they were bred to work, nothing else. You have to feed them more as a trade off for the capability given the technology at the time.

I'll give you an anecdotal example (albeit one backed up by 20 years of engineering experience in the auto industry) to demonstrate my point. Our Ram 1500 with the puny little 3.6L struggles to get 20 MPG highway on a good day. That truck has a lower Cd, a more efficient driveline, a very numerically low final drive ratio, and the most modern controls that an OEM has to offer. You're not going to get anywhere close to that with an older tech worn out engine with higher displacement, especially one that's transplanted into an ancient truck made with Henry's quality steel.

So, I would humbly submit that you go with option 3. You clearly want a little more power out of it, but I think you're getting soured on the cost component. Option 3 is the best balance between time and money in my opinion. It will bolt right up, major supporting components don't need to change, it will be more exciting than stock, and will be more than reliable assuming you install everything correctly and choose quality parts.

Best of luck. Let us know what you do and post your updates. Looking forward to reading what you decide to do.

 

The donor truck? It runs and drives?

How does that compare to the '78 with the blown engine?

Why transplant things if you have an operational, running truck--if in fact you do?

 

yep donor truck runs and drives great. I got it for the price of a totaled truck but repaired it cheap. It’s currently serving as my “don’t give a **** if I put a truck bed worth of gravel in it” and hauling stumps, trash etc. plus always nice to have a spare truck in case my main truck has issues. Not sure why your are questioning it….happy to share pictures of all three of my trucks if you want lol 2017 Dodge, the 78 Ford and the 2004 Silverado.

 

Not JUST fuel economy. I know LS motors very well, that plays a huge part of it. I have built 4 different LS motors and had 7-8 vehicles with them so I know what to expect and how to work on them. Honestly, the part of the swap that’s the worst is the grind of tearing apart the harness etc….those man hours turn from being fun to no fun…

I appreciate your feedback on the option 3 time vs cost.

 

Thank you for your service 93lx1rx7.
Option 5!

 

A lot of this is subjective and depends on what you want. Do you want the truck to be "correct" with the manual trans it came with? Are you fine with a c6? If so the cheapest option to get the truck running and driving is just rebuild the 351M if it's viable. It would be a shame to me to sell the truck if it's in good shape other than needing a powerplant, because really that's one of the easiest/cheapest parts. Body work is a lot worse. Me personally I don't like the LS swap idea and I definitely don't think it's the most affordable but if that's what you want to do and you already dont' have a good engine anyway, why not. You're going to have to probably find different driveshafts if you do that just like you would swapping to the manual trans.

I don't like the 351m/400 and if I had an excuse to go to a 351W or something else I would do it. Depends on the truck though, if it was a pretty much factory correct, survivor truck I would try to stick with what it came with. If it's already a frankenstein who cares. But then the c6 still wouldn't bolt up to anything but a 385 or 335 series

 

yeah definitely not a factory correct or survivor truck so it’s no issue regardless. Honestly would love. 460 because big blocks just sound amazing but that would end up being very expensive because I would need engine and trans etc.

 

460 will bolt right up to your current transmission and frame mounts, they are both the same engine family. If cost is an issue, 460 motorhomes get scrapped everyday, often with very low miles. My cousin had one with 17k miles on it, easy to pull engine as you just cut through whatever is in your way.

LS swaps are cool, but part of what makes these trucks cool is you can fix it with a handful of tools.

 

Does it really? I know the 351m has a bad trans bolt pattern but didn’t realize they rest is interchangeable. How does the rebuild cost of a 460 compare to a 351M/400? What years of the 460 work?

You may have just given me the new/best option yet!

 

1973-1978 for the internally balanced 460 Truck motor. The car 460 will work. All of these came with a front sump oil pan so you'll need to add $280. to get a rear sump oil pan and kit if you have 4wd. The 2979-87 Truck motors were externally balanced motors and some came with rear sump pans if they were 4wd. get as a complete motor as possible the RV route and Van F150-350 had saginaw power steering brackets which if it comes with it all the better, right?

 

You are right power steering would be great. Now I gotta do some research and then some junk yard searching. You all have been awesome, any advice on the 460 would be awesome.

 

If you are really interested in a 460 I have many 460 parts from cores to a long block rebuild bored .020 over " 78' truck motor". PM me and we can exchange e-mails/phone info if you're interested.