decided i wanted to find a 73-79 truck to do a cummins conversion to. Early in the process but going to start getting the parts lines up. looks like the cummins 4Bt would be the way to go. had a few questions.

Ideally like the 76/77 f250 4x4 longed /highboy truck

Think I read somewhere that is is harder to do the conversion to the Highboy trucks. is this an issue?

What would be the ideal stock tranny set up and conversion tranny setup.


I like the 76 grill style, -assuming I found a 78 or 79 is it fairly easy to swap the front headlights/grill to get the round headlight look?

anything else to be aware of or pay attention to.

 

Some 78s came with round headlights already. Sorry, but that's all I got.

 

It depends on how you do the AC, so I'm told - If you do a Dodge-style 5.9 accessory layout, the AC compressor hits the passenger side frame rail on a 78-79, so a narrow frame highboy is even worse, I suppose? But, if you put the compressor somewhere else, there's enough room. I'm in the planning/parts accumulation stages of a 5.9 swap on a '79, and that is one of the tricks/decisions to be made.

As far as tranny, that's sorta all over the board as well - I'm thinking I'm going with a NV4500/OE Ford NP205 transfer case, but I have to move everything anyhow and change drivelines..... So I'm considering using all Dodge (yes, painful). I've been told that an M5OD has great gear ratios for a 4bt, and will fit with the correct rear plate. They seem to be strong enough on most applications, then you could probably go all stock Ford cases and shafts for a newer model, since you have plenty of fore/aft room with a 4BT in the engine compartment (a 6 is a tight fit, so the boxes are where they are underneath, not much room to adjust). OR, you can bolt an M5OD to your stock case, and be all stock from there on.... OR you could use a ZF-5.


Check out 4btswaps.com, theres lots of info there on it.

 

I agree that 4btswaps would be a great place to start, especially considering tranny selection. You definitely want to match your gearing to the output of the 4BT, especially torque. In my '78, I have an NV4500 behind by 6BT, mated to the NP205.

Highboys have about 1 inch narrower frame rails, but that just means different mounts. The 4BT is shorter, so you'd be able to squeeze that A/C compressor in behind the crossmember. You could also sit the motor up slightly higher, though that's not as good as sitting it further back. If you have the skills, I recommend fabricating your own mounts. I don't know if they've gotten any better over the years, but just about anyone who has purchased stuff from Conversion Specialists will advise you to stay away.

Doing a grill swap is straight forward, but it's a question of what you're really trying to do. If you're just going for the round headlights, swap the square '79s for a set of round '78s. Everything else stays the same. If you actually prefer the look of the older grill, it's only slightly more involved. You'll need all the parts of course; grill, headlight buckets, upper grill mounts, etc. The only real mod is that you have to drill new holes for the earlier headlight buckets, as they mount lower on the core support. I just did the swap on mine and it was a piece of cake.

 

thanks for the help--

will look into 4bt swaps.

will do some reading over there, but are you guys more on favor of a 5.9 swap?

is it better to find a truck with an auto tranny from factory or does it matter that much when doing the conversion

what about factory a/c?

 

Here's a link to my build thread......Its a '78 F150 4x4 but may give you some ideas.....
https://www.ford-trucks.com/forums/1...4bt-build.html

 

6BT engines are usually easier to find. IMO they sound better and you've got more power to play with. They are a little tighter to squeeze in but in the scope of the whole project I don't think it makes a lot of difference to the amount of work.

If you are after record breaking MPG then the 4BT might give you an edge there.

On my project I took the whole drive train out of one donor truck - 6BT motor, NV4500 trans, transfer case, radiator, and intercooler.

I started with an automatic ford and converted to manual - had to add a clutch. Going from Manual to auto you will need an auto steering column.

I don't have a/c yet so I can't comment on that. If you get a highboy with divorced transfer case then you can use a 2wd transmission.

Good Luck with your project!

 

lots of good reading and links, thanks for the replies so far!

 

I think 4BT vs 6BT just depends on what you want to do with your truck. I went 6BT in my '78 F250 because it's a big long bed supercab that will do a fair amount of towing. If I we're to do one in my '79 Bronco, I would go 4BT for weight savings and fuel economy, but still great output for wheeling or whatever.

You asked about finding a truck with an auto tranny, are you talking is reference to the engine, our are you planning to swap the transmission over as well? Auto vs manual is preference. I went with an NV4500 simply because my truck was a 4sp. manual when I bought it. If you're asking in reference to the engine, the earlier 2nd gen 12 valves had the lower rated (160hp) pumps in the autos and 175 and 215hp pumps in the manuals. Other than that it does not make a difference.

 

thanks for the help


for the tranny would really prefer and auto tranny when I do the conversion.- just wondering if I come across a good clean truck that has a manual transmission if it is worth picking up or would I be much better off finding one that was an auto trans originally

not totally against the transmission of there is advantages as far as ease of conversion or reliability.

 

Hey, justforfishing
I happened to stumble onto your question.
I have a 1971 4wd f250 " highboy" with a 12v Cummins with a nv4500 trans and a Dodge steering box and pump. I did not do the swap but it looks relatively simple. Some fabled cross members, stock front member cut then a doubler added.
If you still have questions and I can help, hit me up. It drives absolutely awesome. No problems whatsoever. Typically I'm a Ford purist. My 67 f100 has a 429 and my Cummins f250 will be towing it around! It's a great swap.

 

thanks for all the info so far

any comments on this motor? Thinking of going to check it out

https://columbia.craigslist.org/pts/6294719063.html

 

A 6bt is definitely going to be cheaper on the whole. 4bts are expensive little engines. If you can weld and do basic fab work it is not that hard of a swap in a highboy. 2wd or 78/79 f250 would be more of a challenge. The whole swap is not super hard just very time and money intensive.