Cummins 12 valve swap (1 Viewer)

[Dirty Koala]

My main goal is to gain more power, my rig is too heavy when loaded (5 passengers, armor, roof rack loaded with coolers, propane tanks, spare tires etc etc ) going uphill on a highway is very frustrating I’m currently running 35 inch tires and 4.11 gears (original manufacturer size)
With the 6bt I’m hopping to get more power and torque (turbocharger will definitely help)
I’m currently deciding on the gears either 4.56 or 4.88 but honestly I don’t think the gears alone will solve my problems.
Anyways thanks for all the input guys.
Researching is painful specially when is no easy answers.

You definitely will not want 4.56 or 4.88 gears with a 6BT. Remember the torque curve of a 6BT is vastly different from a 1FZ-FE. I have 4.10 gears in my axles and am running 37 inch tires with my 6BT and I will install a 9% overdrive high range gear in the transfer case when I get around to it to further reduce highway speed RPM's.

Out of all the cummins swaps, I believe mine is still the one with the most power running through the drivetrain...significant fueling and other mods when I built the motor...and more sitting on the shelf So far the drivetrain has held up with the exception of my rear driveshaft which snapped whilst climbing a 12' ledge at the end of Hole In The Rock trail...just need to not drive like an idiot when you have 1000ft/lbs on tap.

There are a bunch of us that I listed below that documented our build threads pretty meticulously here as it was all ground breaking stuff when we did them. There are plenty of other builds out there now, but these were the pioneers.

@mryanangel
@thegogglesdonothing
@Mr Cimarron
@Wheelingnoob
@cjmoon
@turbophil
@maxamillion2345

As others have said, the most common way to do this swap is to use an NV4500 as you can adapt that to the HF2AV and it can hold the power no problems. The auto can be done...at least it could when bellhousings were still available, but took a bunch more work to get it to be controllable. CJmoon and turbophil both went the auto route. Max went a totally custom drivetrain route and the rest of us went NV4500 to HF2AV.

Spend a ton of time reading how we all did it, build your plan and figure out if you really want the diesel as its a very expensive conversion. If reading how others have done it is hard research, then you may want to reconsider going down this path, as that is the easy-peasy part. Speaking for myself, I love it and will probably build another Cummins cruiser down the road...75-78 series probably.

 

[Matador]

You definitely will not want 4.56 or 4.88 gears with a 6BT. Remember the torque curve of a 6BT is vastly different from a 1FZ-FE. I have 4.10 gears in my axles and am running 37 inch tires with my 6BT and I will install a 9% overdrive high range gear in the transfer case when I get around to it to further reduce highway speed RPM's.

Out of all the cummins swaps, I believe mine is still the one with the most power running through the drivetrain...significant fueling and other mods when I built the motor...and more sitting on the shelf So far the drivetrain has held up with the exception of my rear driveshaft which snapped whilst climbing a 12' ledge at the end of Hole In The Rock trail...just need to not drive like an idiot when you have 1000ft/lbs on tap.

There are a bunch of us that I listed below that documented our build threads pretty meticulously here as it was all ground breaking stuff when we did them. There are plenty of other builds out there now, but these were the pioneers.

@mryanangel
@thegogglesdonothing
@Mr Cimarron
@Wheelingnoob
@cjmoon
@turbophil
@maxamillion2345

As others have said, the most common way to do this swap is to use an NV4500 as you can adapt that to the HF2AV and it can hold the power no problems. The auto can be done...at least it could when bellhousings were still available, but took a bunch more work to get it to be controllable. CJmoon and turbophil both went the auto route. Max went a totally custom drivetrain route and the rest of us went NV4500 to HF2AV.

Spend a ton of time reading how we all did it, build your plan and figure out if you really want the diesel as its a very expensive conversion. If reading how others have done it is hard research, then you may want to reconsider going down this path, as that is the easy-peasy part. Speaking for myself, I love it and will probably build another Cummins cruiser down the road...75-78 series probably.

Terrific information here sir, thanks for the advise and input I will definitely look into this links the more information the better before pulling the trigger, I don’t wanna be stuck in the middle of a mess without not knowing what to do next.
I will definitely check out the NV4500 like you and other members suggested to do so.
I will keep this thread posted.
Thank you.

 

[Whiskerz]

@Whiskerz ”a quick google” is good. But go ahead and read a bit more than it takes to refute someone. 584 is a completely stripped block. Wet 1fz is around 800. Wet Cummins is a bit under 1100. Not a huge difference. And what does a BB Ford have to do with a anything? I don’t see any area it belongs in this thread.

I used to manage a fleet shop that had 40 6bt and 24 valve trucks. 1100 is light by time you start adding accessories. I did a quick google because I am not familiar with what a 1FZ weighs. The Cummins I am way too familiar with. The 584 number I found list it is a dry long block same as the Cummins number. Apples and apples

 

[mehbohdi]

My Dodge P/U has 4.10 gears and I'm running 34-35 inch tires. I've had this truck 10 years driven and towed all over west coast and would not go with any lower gear. At 1 point I almost considered going to a 3.73 out of the newer trucks, these engines make enough torque you don't need the gearing you need with gas. Like said above do a lot of research before stepping off the cliff, cause its a long trip, swaps can be fun and frustrating. Good luck

 

[LandLocked93]

At some point...there HAS TO BE a better vehicle choice off the trot to meet the needs (or wants) of the OP.
Try govplanet or ironplanet for locked diesels and save yourself thousands in minutes and money.

 

[mjosoba]

I used to manage a fleet shop that had 40 6bt and 24 valve trucks. 1100 is light by time you start adding accessories. I did a quick google because I am not familiar with what a 1FZ weighs. The Cummins I am way too familiar with. The 584 number I found list it is a dry long block same as the Cummins number. Apples and apples

Cool. But I still don’t understand where you’re getting that it’s 3 times the weight? The difference between the two wet or dry isn’t substantial enough to make it an issue.

 

[Dirty Koala]

Weight is a non issue. I have sooo much more weight bolted to my cruiser beyond just the Cummins..hell, my rack, RTT and awning alone weighs 315lbs. I regularly have this truck with all 4 tires off the ground and huck it into corners at speed...I treat it like a big fat rally car.

 

[SegFault]

Why would he want to swap a big block in that gets at best 8-10mpg?

The diesel will get far better gas mileage than any V8 swap, I have a buddy with an L92 (converted to LS3, stock beyond that) and the best he ever gets is 13mpg in his swapped LandCruiser and that’s a far more efficient and lighter motor than some old big block (more power too). The 6BT will get high teens low 20s easily, and have way more torque.

A stripped 6bt Cummins is about 1100 pounds. My big block Ford weighs in at 636 pounds. A quick google says your stock engine is 584 pounds. That is without the heavier accessories and 2 batteries that come with the 6bt. You are talking double the engine weight. A Big block ford looks like a viable swap at this point.

 

[Whiskerz]

Cool. But I still don’t understand where you’re getting that it’s 3 times the weight? The difference between the two wet or dry isn’t substantial enough to make it an issue.

The difference between the 2 engines is over 500 pounds and realistically over 600 pounds. That is a lot of added weight. I like the B series Cummins. I am not sure the gains are worth the over 500 pound penalty that comes with it. Weight is not your friend when you are off road. I do like the idea of a 6Bt with a 5 or 6 speed a lot. At the end of the day it is his truck and if he wants to swap in a B series Honda fine and dandy. I will let ya'll have at this and back out.

 

[maxamillion2345]

40s and 8000 lbs at 75 mph with 12v nets about 17mpg. With 5.38s

 

[Dirty Koala]

I am about 8500lbs fully loaded on 37’s and get 20-23 depending on how spirited I get.

 

[thegogglesdonothing]

My truck is still tuned to stock circa 1995 with a 12v / NV4500 and HC35 turbo, stock injectors, 4.88 diff gears but a 9% underdrive gear for the transfer case (which is a 3.70 drive ratio as best I can tell) and 35" tires.

I haven't ever weighed the thing but with front / rear bumper, winch, sliders, roof rack, rooftop tent, fully loaded drawers, a fridge and two weeks work of camping kit I averaged 18.5mpg on a long camp trip this summer. Doing Interstate driving with my truck emptied out and in grocery getting mode, I get more like 17. It's not a racecar, so I drive it with a gentle right foot, but I'm pleased with the economy, for how much crap I lug around and where I go. And I know it's got more than enough power to handle rock crawling, passing uphill on Colorado mountain passes and every trail I've ever attempted in it.

I totally echo what @mryanangel said - read everybody's build threads, do exhaustive homework and prepare to cut a big check, either of the monetary or elbow grease variety, or maybe both. I cannot more highly recommend that you use all-new parts everywhere in your build though - saving pennies on used parts will bite you in the ass.

I'm at 53,xxx miles on the swap so far and still get a kick out of driving my truck every time I hop in it. It's not all that fun in stop-and-go traffic but it's my adventure toy for life and I will be very excited to one day turn up the wick on the fuel / turbo / tune. For me, I absolutely love the old school, mechanical linkage feeling of the motor and transmission. But it may not be for everybody.

 

[Dirty Koala]

Definitely go with new everything if you can!

As far as power adders...this is my recipe

• New Bosch 4 x 0.13 injectors 155 degree spray nozzles
• 4K governor spring in a 215 P-Pump
• 055 delivery valves
• Modified Cummins lift pump good to 700hp (PDD Hot Rod Pump)
• Tork Tools Adjustable overflow valve
• Timing set at 16 degrees
• Mahle 286210 marine style pistons 155 degree spray pattern
• ARP head studs
• ARP rod bolts
• O-ringed head
• 60lbs valve springs
• Chromoly 10 degree valve spring retainers (needed when going over 35lbs of boost)
• 8.3 Cummins oil pump modified to fit 5.9 block (42% more oil flow)
• Borgwarner K27 Turbo
• 3 piece exhaust manifold
• Power Driven Diesel AFC Live

Just to give you an idea of how quickly costs can add up...the above list cost about $4300 just in parts and none of which actually help with the conversion...they are just parts to make it go faster.

You should factor anything from 10k-30k to do the swap.

10k will be a fairly bare bones swap if you do all the work yourself and don’t do a full engine rebuild and don’t buy any of the above go fast parts.

30k will be a rough all in cost if you have a competent shop do the swap and you do add in some go fast parts.

 

[shocktower]

Is it a diesel or fuel ? You gonna keep the same transmission? And what about the fuel/diesel consumption

Cummins 12 valve is diesel

 

[shocktower]

I guess it is my turn, I have a 97 with a 1st gen 6BT in my rig I use the stock A343F using a stand alone Micro squirt 3V , 4:10 stock gearing, I will be doing some 3.54 soon I did mine 2 years ago I drive it every day I did a build, not a huge write up but a thread you can get the adapter for the NV4500 and run your stock transfer case the weight issue is BS I drive mine like a rally car

 

[Jason Andrews]

Weight is a non issue. I have sooo much more weight bolted to my cruiser beyond just the Cummins..hell, my rack, RTT and awning alone weighs 315lbs. I regularly have this truck with all 4 tires off the ground and huck it into corners at speed...I treat it like a big fat rally car.

I am about 8500lbs fully loaded on 37’s and get 20-23 depending on how spirited I get.

You're at 8,500lbs and you jump it? Got any video?

Another resource to spend some hours on would be 4btswaps.com They have a 6bt section, but it doesn't matter as the 4cylinder version is essentially the same engine minus 2 cylinders. There are obviously a few different parts like turbos and possibly different injection pumps etc but the main parts to swap are the same.

I had my swap done in early 2009 and would mimic what everyone else has said. Figure $10-12k if you are doing the work yourself and 3X that if you are having a shop do the work.

42" tires with 4.88 gears and a .7 overdrive nets me about 19mpg at 65-75mph. I added other mods and finally a second turbo to mine to get the power up well past the stock 6bt numbers since I live at 10,000ft. I run an auto tranny with manual lockup in 2nd, 3rd and 4th. Most everyone I've seen runs a NV4500 and @NLXTACY makes an adapter for that I believe.

 

[Dirty Koala]

Your at 8,500lbs and you jump it? Got any video?

Another resource to spend some hours on would be 4btswaps.com They have a 6bt section, but it doesn't matter as the 4cylinder version is essentially the same engine minus 2 cylinders. There are obviously a few different parts like turbos and possibly different injection pumps etc but the main parts to swap are the same.

I had my swap done in early 2009 and would mimic what everyone else has said. Figure $10-12k if you are doing the work yourself and 3X that if you are having a shop do the work.

42" tires with 4.88 gears and a .7 overdrive nets me about 19mpg at 65-75mph. I added other mods and finally a second turbo to mine to get the power up well past the stock 6bt numbers since I live at 10,000ft. I run an auto tranny with manual lockup in 2nd, 3rd and 4th. Most everyone I've seen runs a NV4500 and @NLXTACY makes an adapter for that I believe.

No videos, need to get a photographer out on some trips I guess.

Do you have a link or pics to your compound setup? Real estate under the hood is tight..would like to see where you stuffed your turbos.

 

[Jason Andrews]

No videos, need to get a photographer out on some trips I guess.

Do you have a link or pics to your compound setup? Real estate under the hood is tight..would like to see where you stuffed your turbos.

Here is one of what it looked like being built and before he added in the external Tial 44mm wastegate. Check out @jonvigil82 and @vi.engineered on Insta. He does some sick work and made it look like a cake walk. The main thing that makes my setup work is that I run my giant air filter atop the snorkel instead of under the hood.

Now back to the OP tech...