The official 6bt conversion thread

[mljjones67]

Thought I would put up an official thread for the 4bt. Didn't want to continue to hi jack the other thread!! I think this is an awesome idea.
Here is a couple web pages I have found so far!!
http://www.4btswaps.com/forum/showthread.php?t=242
http://www.4btswaps.com/forum/index.php

[nevrenufhp]

Very nice way to be able to drive a full size truck on a daily basis.

[mljjones67]

Here is the start of this discussion on another thread.
http://www.fordification.com/forum/view ... 020#196020

[averagef250]

I'll get some pics of the 4BT in my '71 hopefully tomorrow. I will also be putting a 4BT into a '94 F-250 4x4 next week. It has a great running injected 300 in it that will be up for grabs too if anyone's interested. I'll be taking lots of pictures of the whole process on this one. I'll also be learning quite a bit about what engine electrical stuff a '94 F-250 does and does not need for the gauges to work right with a diesel that only needs one wire to run. I'll need to drop the tanks and switch them out for the 87 to 89 style with the low pressure fuel pumps. We'll likely be aftercooling this one as well. Might go as far as porting the head and camming it too.

Have you found any 4BT's or a 5 speed for sale locally Mike?

The pic is the only halfway decent one I have of my '71 right now. Just put here so you guys could see what kind of truck can pull down 25 MPG with a 4BT.

[FORDification]

Thanks for the link, Mike. I've just added those forums to the Automotive Messageboards Master List on the Links page.

[mljjones67]

No problem Keith
I have not found one yet. I haven't really looked other than in the local classifieds. I like the flat bed on your truck. I think I might go that route too. I would like an aluminum one though. Do you like it better than the regular bed?

[averagef250]

I prefer a normal bed myself, but really depends on what I'm doing with the truck. I don't feel guilty when I throw chains or parts on the flatbed like I would if it were a real nice bed. The diamond plate flatbed I built is real stout, but actually weighs less than a pickup bed. The headache rack looks real sharp and gives the truck a tough look, the burly 4BT rattle doesn't take any away from that either.

My '70 has a nice bed that I rarely put anything in with a toolbox up front. Everything I need usually fits in the toolbox and half the time I'm towing a trailer so I don't need the bed.

[theskytoucher]

Could we get a thorough definition of wat a 4bt is just so everyone knows exactly wat we are talking about here???
Thanks

[theskytoucher]

Thanks!!!!

[19674x4]

I'll get some pics of the 4BT in my '71 hopefully tomorrow. I will also be putting a 4BT into a '94 F-250 4x4 next week. It has a great running injected 300 in it that will be up for grabs too if anyone's interested. I'll be taking lots of pictures of the whole process on this one. I'll also be learning quite a bit about what engine electrical stuff a '94 F-250 does and does not need for the gauges to work right with a diesel that only needs one wire to run. I'll need to drop the tanks and switch them out for the 87 to 89 style with the low pressure fuel pumps. We'll likely be aftercooling this one as well. Might go as far as porting the head and camming it too.

Have you found any 4BT's or a 5 speed for sale locally Mike?

The pic is the only halfway decent one I have of my '71 right now. Just put here so you guys could see what kind of truck can pull down 25 MPG with a 4BT.

you get 25 mpg in that thing, wow

[averagef250]

It's hard to get worse than 20 with a 4BT. The bread trucks that most of these engines came in weighed several tons, were as aerodynamic as a barn and ran 3 speed autos or 4 speeds with 4.56 rear gears. The bread truck engines spend most of thier lives on the governor and they still got 15 MPG or better.

nevrenufhp is right about other adapters out there. There's ways to bolt a cummins to just about any transmission. The Cummins makes quick work of most autos though, I'd strongly recommend a manual. If you're going to bump one up, you'll also want to go with the dodge NV4500 bellhousing and tranny. With that you can run a 13" clutch. The SBF style adapter limits us to a 12" clutch that, even with the best organic clutch, will slip over the 300 horse range unloaded, less than that towing.

300 horse and 700+ lb/ft is very easy for under, possibly far under $500 in ebay/craigslist parts. What the guys bumping up thier 5.9's don't want is what the 3.9 loves.

As far as starter and gauges, if you get one from a a ford chassis bread truck the sensors are correct for our trucks gauges. The starter has it's own high capacity relay built in, the fenderwell mounted one won't handle the juice. I just run a 10 awg wire from the existing starter relay to the "S" terminal on the starter. I make all my battery cables from 4/0 and 6/0 welding cable and solder and shrink tube the ends. The 4BT takes a lot of juice to start, but they start instantly. One big battery will start it fine. Just a key tap and VROOM, RATTLE, RATTLE.

Another thing worth mentioning, These engines are very heavy and very efficient. They hardly need a radiator. The stocker 3 core 300 six radiator with a small electric fan is all that's needed to cool one of these.

Probably the most expensive part for the conversion is a power steering pump. Most of the breadtrucks only came with a vacuum pump for power brakes. Most of use like our power steering though. I try to run the first generation dodge 5.9 saginaw pump, I've been lucky and found them with the extra return for hydroboost. These pumps can be upwards of $150 on ebay and sometimes very hard to find. You can usually find several combination PS and vacuum pumps for sale on ebay, but these are almost always $200++ and they are very expensive to rebuild when they go out. I figure the point of the diesel is simplicity so I stick with the standard, proven saginaw pump and convert to hydroboost power brakes.

[ChrisB]

I can testify to the lack of cooling capacity needed for this and similar engines. By VIN lookup my 72 came with a 300 I6. It now has a 6BD1T(5.8L inline 6 made by Isuzu). I'm not sure if the radiatior is a 300 replacement or something for a 360/390, though I suspect the latter based on some pics I've seen at Summit. Anyway the inlet and outlets were moved on a top-bottom flow factory copper/brass radiator very similar to what I have in my 69 with a 360 originally (now 500 Cad).

It has an unshrouded mechanical fan, which almost seems unnecessary. Coolant temp typically takes its sweet time getting up to 170 indicated and then stays there as long as I have some load. At idle it gradually falls a bit.

The biggest test for cooling was pulling 6-7K up the Las Vegas towards Baker, CA grade in mid 90* temps. 30-40 mph at 2200-2400 rpm with 5-7 psi boost for however many miles that is climbing from roughly 2000 ft to about 5000. The temp rose to 180 but took a long time to get there and came down to 170 immediately at the top of the hill.

The fact that it no longer held the normal temp, means cooling system was beginning to be overtaxed as the temp climbed with the Tstat theoretically wide open. It was so mild and the final temp of 180 (assuming correct) is so mild it is a non-issue.

I would assume a 4bt or 6bt at a similar power level would need about the same, with an edge to the larger engine needing more, but not by much.

The 500 powered 69 would pull that same task easily but probably at 220-230*. It has the same sized radiator and mechanial fan with a shroud.

[averagef250]

I plan to run the factory supercool radiator and shroud with the 6BT in my '70. The 6BT will be up around the 800 lb/ft mark and will pull in excess of 25K regularly (17K pound D47U cat and 8K pound trailer). I may upgrade to a Dana 80 for the rear. I saw a dodge D70 the other day with it's ring gear side carrier bearing squished an 1/8" into the axle tube from cummins torque.

I pulled that weight over the steepest passes we have here with the old 390 in 4th gear, 2500 RPM and 1/2 throttle and the water temp was around 210 with the supercool on an 80 degree day, the oil was probably around 300 though. 15 miles of straight up with that load the 390 only had 25 lbs oil pressure at the top, usually ran 55.

[hardtailjohn]

Dustin, what rear ratio are you running? I guess I'm asking what RPM the little Cummins is happy at??
JH

[averagef250]

4.10's and 35" tires. The gear spread is perfect with the close ratio M5R1.