It's no secret that I am gearing up for a Cummins 5.9L swap in my 80 F150, and I have already sourced an engine. I know this will add 300-500LBS to the front of the truck, depending on which trans I use. The NV 5 and 6 speed manuals are cast iron case, making them 200-300LBS alone.

The 80 has king pin I-beams, and these are the same king pins used under the later F250/350 2wd, even with the 6.9L IDI diesel, which wieghs almost the exact same as a Cummins 5.9L. I'm not the least concerned about the suspension being able to hold up to the added mass.

However, the 80 and early 81 have the famous "Swiss cheese" frame, whether F100 or F350. Mine is still in great condition, even showing some areas that still have the factory black coating, as thin as it was applied back then. Heck, even the floor of the cab and underside of the bed look good, showing the gray primer/sealer that was applied to the entire body, before the parts that show were painted red. I guess they just didn't spray color on the underside, at least not on the very early 80 models like mine (among the first 10K units built using the "new" body style).

That said, is there any reason for me to have concerns about the frame? It's solid and rust free, not counting a bit of surface rust. I really intend to make this truck see me to the grave, but not anytime soon.

The engine I have bought has already seen one frame die from the stress of holding it (early D250 "flatnose" that really remembles the "bullnose"). I'd hate to see it go thru that again...... Of course, those early D250/350 frames were known as the weakest link, even with the weak trans and rear diff.......

I can get a later frame (82) pretty easy. Would I be crazy to not use it?

 

With the engine in-between the two front tires, I don't think you have to worry about the extra weight. I bet it would be fine if you are not hauling a lot of weight, which you shouldn't be anyway with a half-ton axle, brakes, and springs. If you upgrade the suspension/axle though, you might as well upgrade the frame. I guess it depends how you plan on using the truck. If it's to commute/haul stuff/or a toy and you plan on dumping the clutch at the redline..

 

I don't plan to drive it any different than I always have. Of course, that does entail towing *small* loads, like this:

 

If that is all the harder you figure on working it, and you don't drop the hammer on every shift, you should be fine. if you were to work it the way we do the 92 or the 86, then it wouldn't survive. It is all in your needs and intentions. The 6BT will twist up a frame no matter whether it has extra holes or not. It is all in how you drive it, load it, and also how much you turn it up.

One thing to add, the NV4500 is a hydraulic clutch, so you will have to add that into the conversion fun. The slave on the NV will hook up to the line from the ZF or T19 though. It is an external slave at least.

 

I have to ask a few whys here, why a cummins, why an F150? If you have a use for a 5.9 cummins why don't you also need a sturdier truck to begin with?

That said sure technically the frame can carry the weight, and it sounds like you've researched some of it. But how long will everything else last, front wheel bearings, brakes, rear axle, and the body. Ford frames, even F350 frames are very bendy/springy, this is a double edged sword. Back in the day I put a big engine in my Jeep, this twisted my frame into a pretzel, it sprung in one direction with all the torque and didn't spring back. I'd expect your frame to bend A LOT, and sure it would likely spring back, BUT will your body that is attached to it. This is the kind of thing that twists and breaks body mounts, and bed spot welds, etc. Next thing you know your doors and tailgate won't open and close right and your windshield has a huge crack across it.

So I think it's a VERY good idea to step up on frame and drivetrain. Why not find a cheap later F350 and use it's frame/springs/axles, etc?

 

Agreed. If you want a 3/4-1 ton engine, then use a 3/4-1 ton chassis

Fo a F150 a BT4 would be more appropriate

 

Same could be said for Powerstrokes and the old IDI's, but they are put into Broncos and 150s all the same.

We have over 100,000 hard worked miles on our 92 F350 with the Cummins. It was put together to work hard, and it has done it quite well. We did recently beef up the drive shafts due to regular u-joint failures. Structurally, nothing has been done. Wheel bearings have been fine.

I agree that these are not F150 bearings and frame, but the fact remains that people do these swaps because they want the fuel efficiency from the diesel. Some do it for the "cool" factor. For the money, I would rather a 6BT than a 4BT, as around here the 4BT's actually can run higher prices than the 6BT. the fact teh on in the 92 survives is a testament to their durability in that my sister does not take very good care of it, and it is her truck...

 

Simply put, the engine is tired, and never got better than 15 MPG.
Why a 6BT? I have one already, and got it for WAY less than a 4BT typically goes for, without the vibration of the 4BT.
Heck, even the 4BT weighs quite a bit. 2/3 the engine with 3/4 the weight.

I'm not looking to build a "hot rod". I've got one (more really). I'm expecting MPG to be in the range of 30. If I were trying to build a hot rod, I'd start with a 24V, for the better flowing head. they can be converted to use a P-pump rather easily. Not cheaply, though.
Heck, the engine I bought has seen 120K miles, and is detuned as much as Cummins could do, in order to save the weak auto trans it was attached to. I'll add an intercooler because they really help lower EGT's, and bump the wastegate up to the mid-upper 20's, where it was set for the 5 speed trucks.


I know the NV4500 has an external slave, and that I will need pedals for 84-86. I did not know it was that easy to hook into the Ford system. i appreciate the info!

 

You will want to reinforce the area where the slave mounts to as well. There are kits out there to do this, as firewall flex is a common issue on these trucks. My 86 suffered a failure as well. I might be able to help out on the pedals too, but my turnaround time is kinda slow sometimes. I have one set still in a truck right now, I would have to look in the one truck to see if there is any others loose, but I have my doubts. (I bought one a while back with a pile of extra parts...)

 

Yeah, I plan to brace the firewall around the clutch master.
Would be cool to have a set of pedals handy....... Even though I don't have a trans yet.

 

Well then it's a money thing, at which point doesn't it become more cost effective and safe(as in known quantity) to sell what you have and buy/build an IDI/5 Speed truck?

I would consider it a safe assumption that the value of your current truck with the tired engine plus the value of the cummins plus the cost of the tranny and everything else you need, and of course the value of your time is a lot more then the cost of a really nice IDI/5 speed truck. Shoot the value of a NV4500 alone is enough to buy an IDI/5 Speed 2wd F250.

 

Don't want an IDI. Not my thing. I like the simplicity of the Cummins engine. Doesn't hurt that I have a customer who has 1.8 MILLION miles on his 2001 24V/6 speed........

 

In what world is a cummins in a F150, let alone just the 6bt cummins less complicated then a stock IDI?

If that's your thing, that's your thing, just don't get your reasoning.

 

I know a Cummins will way out mile an IDI or PSD, my friend has an IDI and he keeps it up ok but it's tired with only 300K, and my dad has a PSD that's a little iffy already at 280K. Then I know a guy with a 5.9 Cummins that has 1.2mil and still going strong as ever haha Cummins is THE diesel engine IMHO.

 

Subscribed. And watching to see if my '82 frame is going under an '80 - although it has ball joints.