The official 6bt conversion thread

[sgs]

Thanks for the reply Av.F250,

So the 4.5 now doesn't sound like my answer. I maybe wrongly assumed that it would be an almost direct bolt in. Would the bell housing araingement from my 4BT fit the 4.5?

Now if i understand you correctly, you have a 4.5 running in your truck, or are you mid stream? Why are you converting to front gear train?

sgs

[averagef250]

All 4.5 HPCR engines (2003 and newer) are rear geartrain along with just about every other variation of the B series Cummins EXCEPT the ones that dodge uses. The new engines do not have a front timing cover. All the accesories, the camshaft and HP pump/IP are driven off the rear of the engine. The engine block itself has the same rear pattern, but the timing cover bolts to it and the transmission adapter bolts to the timing cover. The timing cover has a completely different pattern than the rear of the block. The crankshaft pattern is still the same, but the crankshaft itself is 2+ inches longer than the older front geartrain crankshafts.

To convert to front gear train I am having my 4.5 crankshaft cut apart and welded back together. I have to drill and tap all the holes in the front of the block for a front timing cover and I have to have the foremost camshaft bearing bore machined to accept a bearing since the rear gear engines have the cam bearing in the rear and a cover up front. I'm still undecided what injection setup to run. I was going to go with an inline pump, but I've been leaning more and more towards running the actual HPCR injection. I want 300 HP and 650 lb/ft from this engine. From what I have experienced this should be an easy feat with a 16V four Cummins. The 16V motors have the efficiency advantage of centered injectors. I'm hoping for the same 25 MPG average as my 8V 3.9 at 200HP with the 16V 4.5 at 300HP.

My engine's not running. It's disassembled on a stand while I scratch my head and try to save money to do what I want with it.

If you want a 4.5 HPCR engine, the easiest way to make it work is to run a 1000/2000 series Allison automatic. All the rear gear on the road engines I've seen have had Allison autos behind them. You can bolt up an industrial (non-GM) Allison 5/6 speed to the SAE3 rear geartrain adapter and control it several different ways.

There's also a lot of meat to the transmission adapters on the rear gear engines. You could machine one to fit any stick tranny you want with a custom flywheel. Thats if you can fit the rear geartrain in your truck.

For me, rear gear just doesn't work. I have a plan of what I want and front driven accesories are important to get everything the way I want it. A Cummins under the hood looks right with front geartrain. They are one ugly SOB with rear geartrain. If you saw my 4.5 CR engine you would not recognize it as a Cummins four banger.

[68Mercury250Ranger]

Hino did the same thing in around 98/99 on their 4cyl diesels.
older 4cyl was a 4.5 litre with front geartrain and aprox 130hp intercooled, the next generation was 5.0 litre 4 cyl with overhead cam/16valves and rear geartrain, and 150hp.

I had thought about using a later model with rear geartrain but the firewall shape of the 79 and prior Ford trucks wouldn't allow it......and I hate bodylifts I could not find any good used earlier 4cylinders in my pricerange so I gave up.

Hino 4 cylinders all came with Allison 4spd when automatic option.

the hino engines are way too expensive to repair, but they do have "drysleaves"

[69F110]

I ran across a 69 Ranger with a 4 cylinder Isuzu Diesel last week. The owner said it gets 35 MPG. Besides that, the truck was rust free and clean as a whistle.

[sgs]

Thanks to all that have given suggestions here. Now all you Cummins guys can get P.O.'d at me. I made the decision and ordered the parts from Survival. I'm replacing the 4BT with a FE, 445 CID. The reasoning? It's hard to say. probably because I know it fits, know it won't have a vibration problem, and know it won't have a noise problem.The truck is a pristine frame off 73 F350 crew cab 4X4 and I'm tired of looking at it. I want to drive it this summer. Yes,I know it won't get 20 mpg. The truck does have a Ranger overdrive so the 445 will turn about 2,000rpm at 60 mph, and hopefully won't be too thirsty.

So the 4BT and all the parts for installation are still for sale.(check the classified threads) If no one here takes me up on my previous offer,they will go on E-bay when I get around to pulling it apart.

sgs

[68Mercury250Ranger]

No reason an FE can't be fuel efficient, but that is one bigazz truck. mix the right cam/carb/intake etc. and you should have a strong pulling truck.

you will probably run headers and through muffler just so it will make some noise

I would buy up the 4bt package if my hours were still rolling in but we are well under 40 hours a week now. it sounds like a good deal to me .

Good luck with your reverse swap..

[1971ford]

Bump.


How much louder is a 4bt than a 6bt if at all?
How much more does the 4bt shake than the 6bt if at all?

I have heard the 4bt is louder and shakes terribly

And also, i am having a hard time deciding between 4bt and 6bt if i do go cummins.
I'll be towing the race truck on a big flatbed. truck and flatbed seen here. The truck weighs 4650. Trailer i am guessing 2750. Total of 7,400. However i would also like to fill the flatbed on the highboy with a 300lb dirt bike, and 200 pounds worth of camping gear so total of something like 8,000 plus weight of highboy which i'm guessing is 5,000.

I will be towing this twice a year. Then i'll be flat towing my buddie's suzuki samurai crawler frequently but that weighs nothing.

Truck is a daily driver and sees highway use every day. I also take it on 4x4 trails in the mountains.

4bt
Lighter
6 or 7 more MPG's
Easier swap, no cutting crossmember, easier motor mounts, plenty of room

6bt
More power than i know what to do with
Heavy, more stress on d44 front axle, more stress on drivetrain from torque
6 or 7 mpg's less


Basically i really just need to know for sure that the 4bt would be able to tow 8,000 lbs over the mountains EASY.

[averagef250]

4BT is exactly 2/3 of a 6BT. There's nothing there to make one louder than the other. Well, many dodge engines have sound insulating materials on thier pushrod covers and double layer oil pans. Those parts don't do much.

4 cylinder diesels have more of a "tractor" note to thier exhaust. This is all relative to engine cam, pump timing, turbo, exhaust, etc. A stock 105HP 4BT with full exhaust and a muffler is pretty darn quiet. A 3" straight pipe on the same engine and it sounds exactly like a farm tractor.

4 cylinder inline engines do not balance perfectly. Just a fact of physics, nothing you can do about it. A four will NEVER be as smooth as an inline 6 at an idle, but anywhere above idle and the difference is negligable.

More than anything else, many 4BT's are from old worn out breadvans that got sub-par maintenance. If a 4BT is shaking bad enough at idle to be noticeable in a fullsize truck there's something wrong. Usual suspects are bad injectors and headgaskets. Compounding the problem is breadvan fleets replaced worn engines and even performed initial 4BT repowers with "Cummins Reman" engines that, frankly, were just farmed out cut rate bearing/ring jobs. 9/10 Cummins reman engines I've seen have been a real small step above a Krylon rebuild.

The six cummins is a lot of engine for any older truck engine compartment. It's just plain long and tall. The 4BT and other 4 diesels will fit fine in the highboy chassis because the front of the engine sits behind the engine crossmember.

[1971ford]

Thanks for the info Dustin.
I snuck a edit in my last post regarding the capability of the 4bt for towing vs. the 6bt. I read the whole thread among many others and 95% of people are doing the swap for strictly the mpg's and not much info on how they tow.

I'm leaning towards the idea of buying a complete, running/driving dodge pickup with 6bt and a manual trans for $3k and pull EVERYTHING I need from it (6bt, trans, radiator, intercooler, exhaust, fuel delivery, and who knows what else).

But a lighter and even more fuel efficient 4bt is still on my mind. Theres this on craigslist http://sacramento.craigslist.org/pts/2604199225.html
Although I dont have the money right now (i'd have to sell off the gas engine stuff first).

[Ranchero50]

We have a big Skytrack at work with a 4bt and inside the building it's just plain loud, seems louder than a 6bt pickup at idle.

The 6bt is a monster in our engine bays, you've seen the builds... If you can keep it back in the firewall well and as low as you can it should fit. Duckbill's turned out well. Mine with the 2wd required a lot of compromises.

Jamie

[1971ford]

yeah if i go 6bt i'll make it fit. I've spent probably 15 hours in the past couple days looking at every cummins into ford swap i can find. I'm starting to get a pretty good understanding on the basics of dropping one of these in a highboy. Still not sure on what trans i should look for if i go 6bt.
I want to just pull the whole 6bt and trans combo out of a dodge and drop it right into the highboy. How is the factory dodge 5 speed that came behind the cummins? Then hopefully i can just shorten the intermediate driveshaft down to pretty much nothing and still use my dana 24 t-case (with a hefty support bar added, and eventually a np205 swap). Almost all the info in this thread is 4bt stuff and i see if i happened to end up running a 4bt, i'd go with the mazda 5spd.

Then i could just take my radiator to the shop and swap the bottom hose (the outlet?) over to the passenger side and use that radiator, and stuff the original dodge intercooler between the grill/radiator... change the intercooler pipes a little as needed...
Change the original dodge downtube a little if needed..

[Ranchero50]

I had to use a '90's Ford truck crossflow radiator, there's just not enough room for either stock radiator. Mine is about 80% done. I didn't work on it this summer because I've been working nights.

Transmissions are the weak link. Regarless of which route you go (Ford or Dodge) the 6bt can over power them. I chose a Dodge 4 speed auto with lock up converter, hoping for mileage and ease of installation. If I were you I'd try to find a '95-'98 truck with the better parts.

Jamie

[nevrenufhp]

......
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But a lighter and even more fuel efficient 4bt is still on my mind. Theres this on craigslist http://sacramento.craigslist.org/pts/2604199225.html
Although I dont have the money right now (i'd have to sell off the gas engine stuff first).

Looking at that ad, I notice there's no shot of the pump. I'm betting it was a stationary engine with something like a Lucas CAV pump.

[fireguywtc]

The 4BT is definetly a better swap for milage and fitment, but as you noted, the 6BT is probably easier if you have the whole doner truck to get all the parts. I like the idea of the 6BT better, but thats my opinion. You can get it done either way for your demands.

The NV4500 5spd is strong enough for your purposes, but the gearing is less desireable then a ZF5. The ZF5 is like the NP435 with an OD gear. The NV is weird because the 1st gear isn't granny but its almost too low for starting out in. 2nd gear is almost too tall, but when empty and cummins will pull it. But again for your uses of daily driver and occasional tower, it would work just fine. After all they used them in one ton trucks. As long as you don't abuse it or really up the HP it will suit you fine. The NV4500 would also be easier to fit into the highboy then a ZF5. I would think you can find a good 2wd doner truck in your budget.

[averagef250]

......
.....

But a lighter and even more fuel efficient 4bt is still on my mind. Theres this on craigslist http://sacramento.craigslist.org/pts/2604199225.html
Although I dont have the money right now (i'd have to sell off the gas engine stuff first).

Looking at that ad, I notice there's no shot of the pump. I'm betting it was a stationary engine with something like a Lucas CAV pump.

Exactly, that's a pump or genset engine right there. If it has an A or P3000 though I'd grab it up at that price.

Ryan, what you're towing isn't a problem for either engine.