2 Engine Plans

[BroncoManSam]

I've been comparing 2 different engine build plans for my 1973 Bronco resto. I'm looking for opinions, and pros and cons on both. I'm building this Bronco to be easily trail capable, but also drivable, in some regard, on the road. I'll make a list of each plan with some basic specs.

Plan 1:
-Engine: Original 302 (rebuilt and stroked to 347ci, 350hp and about 350-400 ft/lbs of torque, Holley Sniper EFI)
-Trans: Tremec TR4050 5 speed manual
-Transfer case: Atlas II
-Axle gears: 4.56s, air lockers front and rear
-Tires: 35x12.5x15r
-Suspension: 3.5inch Duff lift with 2in body lift.

Plan 2:
-Engine: R2.8 Cummins turbo diesel crate engine (spec'd at 161hp and 310 ft/lbs of torque)
-Trans: Tremec TR4050 5 speed manual
-Transfer case: Atlas II
-Axle gears: 4.56s, air lockers front and rear
-Tires: 35x12.5x15r
-Suspension: 3.5inch Duff lift with 2in body lift.

I'm not comparing price right now, I'm mostly curious as to other benefits the Cummins would provide, other than improved fuel mileage, especially considering the torque and horsepower specs of both. Is there any reason to even consider the Cummins over the 347? My first judgement would be to go with the 347 because of the HP and torque, but I am definitely not an expert and would like to know more/other opinions.
I also found an R2.8 crate engine with the TR4050 already bolted on and ready to go from this site: https://quickdrawbrand.com/.../cummins-r28-tremec-tr4050.../ Seems like a decent price for the package.

Thanks in advance for any knowledge/advice.

 

[ame]

I am in the same part of my build and was planning on either a 351 or 2.8 Cummins, my biggest hesitation with the Cummins is a lack of aftermarket support for the Bronco platform yet as the few I have seen have taken extensive work to make it fit but 20+mpg would make it a lot more feasible to drive then 10mpg.

 

[SteveL]

With an od tranny and 35's you may want to look at 4:88 gears

 

[BroncoManSam]

I am in the same part of my build and was planning on either a 351 or 2.8 Cummins, my biggest hesitation with the Cummins is a lack of aftermarket support for the Bronco platform yet as the few I have seen have taken extensive work to make it fit but 20+mpg would make it a lot more feasible to drive then 10mpg.

That's what I've been thinking about too, since they're relatively new. I'm sure in time there will be support for Broncos. The latest Ultimate Adventure build from 4Wheel and Offroad Magazine built a Jeep with the R2.8, and they've built some other rigs with the R2.8 so they are gaining in popularity. If I remember correctly, there was an R2.8 on display at Super Celebration East this year.

 

[BroncoManSam]

With an od tranny and 35's you may want to look at 4:88 gears

Just did some gear calculating with the setup I listed. At 2200 RPM I'll be at 50mph in 4th gear, and 66 in 5th. At 3000 I'll be at 69mph in 4th gear. I'll put in 4.88 and see what I come up with.

 

[Broncobowsher]

That is 2 completely different directions. Really going to depend on what you want.

I only drove one R2.8 and it was pretty nice. It happen to be a Cummins R&D rig. And they were telling how nice it is with a manual transmission (I didn't get to drive that one).

I would lean toward the R2.8 if I were building one. Not a hot rod, but a nice diesel with the minimal emissions tacked on (no DEF, I think it is only a cat and not a DPF, etc.). A more complex build, but I think a better product when done.

 

[BroncoManSam]

That is 2 completely different directions. Really going to depend on what you want.

I only drove one R2.8 and it was pretty nice. It happen to be a Cummins R&D rig. And they were telling how nice it is with a manual transmission (I didn't get to drive that one).

I would lean toward the R2.8 if I were building one. Not a hot rod, but a nice diesel with the minimal emissions tacked on (no DEF, I think it is only a cat and not a DPF, etc.). A more complex build, but I think a better product when done.

With all the time I have waiting for parts, I've been coming up with as many possibilities as I can haha, no shortage of ideas. Oh wow, sounds like a great opportunity there. Yeah I was wondering how it would fair with minimal emissions. If I could squeeze just a little more horsepower and/or torque out of it, I'd try, but I'd still be happy with the stock numbers considering the improved fuel mileage.

 

[Broncobowsher]

The R2.8 is 100% new.
A 347 starts with a used engine and is rebuilt. Unless you go with an aftermarket block but your build level is now where near needing the support of an aftermarket block.

The 2.8 sounds expensive, until you really put it in perspective. Go price a ford Motorsports 5.0 coyote (another 100% brand new engine), don't forget to add in the harness, computer, sensor package... For all that you get with the 2.8 it is actually reasonably priced.

 

[BroncoManSam]

The R2.8 is 100% new.
A 347 starts with a used engine and is rebuilt. Unless you go with an aftermarket block but your build level is now where near needing the support of an aftermarket block.

The 2.8 sounds expensive, until you really put it in perspective. Go price a ford Motorsports 5.0 coyote (another 100% brand new engine), don't forget to add in the harness, computer, sensor package... For all that you get with the 2.8 it is actually reasonably priced.

After I started adding up the cost of having the 302 rebuilt and stroked, plus the additional parts, wiring, trans, etc, it about added up to the price of the R2.8 and trans put together, so the the Cummins might be actually more viable in terms of cost.

 

[Digger556]

I've been comparing 2 different engine build plans for my 1973 Bronco resto. I'm looking for opinions, and pros and cons on both. I'm building this Bronco to be easily trail capable, but also drivable, in some regard, on the road. I'll make a list of each plan with some basic specs.

Plan 1:
-Engine: Original 302 (rebuilt and stroked to 347ci, 350hp and about 350-400 ft/lbs of torque, Holley Sniper EFI)
-Trans: Tremec TR4050 5 speed manual
-Transfer case: Atlas II
-Axle gears: 4.56s, air lockers front and rear
-Tires: 35x12.5x15r
-Suspension: 3.5inch Duff lift with 2in body lift.

Plan 2:
-Engine: R2.8 Cummins turbo diesel crate engine (spec'd at 161hp and 310 ft/lbs of torque)
-Trans: Tremec TR4050 5 speed manual
-Transfer case: Atlas II
-Axle gears: 4.56s, air lockers front and rear
-Tires: 35x12.5x15r
-Suspension: 3.5inch Duff lift with 2in body lift.

I'm not comparing price right now, I'm mostly curious as to other benefits the Cummins would provide, other than improved fuel mileage, especially considering the torque and horsepower specs of both. Is there any reason to even consider the Cummins over the 347? My first judgement would be to go with the 347 because of the HP and torque, but I am definitely not an expert and would like to know more/other opinions.
I also found an R2.8 crate engine with the TR4050 already bolted on and ready to go from this site: https://quickdrawbrand.com/.../cummins-r28-tremec-tr4050.../ Seems like a decent price for the package.

Thanks in advance for any knowledge/advice.

I've been down this road. My rig started out with a decent carb'd 351W, 375HP/400+lbft. When I first bought the Bronco, it made a whopping 9-10 mpg with questionable driveability. (poor cold starts, warm up, fueling control over rpm range) Made lots of power and burned lots of gas. With the OE 12 gal tank, I was filling up every 100 miles. ?:?

I changed cam, exhaust, intake and added a homebrewed TBI injection system. Driveability went way up, mileage climbed to 14mpg. Plugs showed the engine was running much cleaner. Switched to a 23 gal tank, but driving range was around 230 miles. Better, but not on par with current production vehicles. It got worse when towing.

Around this time Cummins re-tuned the R2.8 and bumped torque to 310 lbft. RPM and weight are comparable to a V8. Since I live in CO, mountain driving and altitude power loss are very real. Minus 15-30% hp and torque. This makes the R2.8 on par with the V8 power under certain, but critical conditions. (10,000ft passes) I pulled the trigger. The R2.8 is priced decent for what you get and ROI over the V8 is pretty good with the mileage improvements.

Here are the plus's of the diesel over the V8
- Brand new engine, alternator, PS pump , etc. All new
- Cummins reliability
- Very complete package. Computer, wiring, gas pedal, gauge, very good install manual
- Turbo power!

Here are the drawbacks:
- The Cummins takes a lot of ancillary equipment. Intercooler, PS reservoir, coolant expansion tank, remote oil and fuel filters, extra plumbing, etc The Bronco engine bay is small and it's hard to fit this all in. (Although I've figured most of this out, so skim my thread for ideas)
- Cummins will require frame mods. I had to make new engine mounts and modify the crossmember. There may be clearance issues with std width front axles. The oil pan is wider than a Windsor block. (With full widths, clearance is not really an issue and the pan doesn't hang down as far.)
- You will be largely on your own figuring out problems. Cummins has decent engine support, but no help with the rest of the integration. The RepowerOwners website is okay, but far from great for support.


For gearing, don't go deeper than 4.10s with 35s. I ran 4.56s and 37s with the V8 and will continue running them with the R2.8. There is an RPM calculator on the Cummins website. With my setup and for 4.10s/35s, you will be well into the diesel's power band. You will be beyond the optimal efficiency range. Remember that engine torque peaks at 1800 rpm.

Since I mentioned it, be careful comparing power and torque numbers between gas and diesel engines, they don't tell the whole story. My 7.3l diesel is old and only make around 190hp, but it would out-pull that 375hp V8 all day. Why? Diesel make much more drivable power. V8s with performance cams push peak torque up between 3500 and 4500 rpm. This is hardly where you want to be hanging out when towing or climbing a long grade. Diesel typically peak below 2000 rpm. Below 3500rpm, I bet the 2.8 feels more powerful or at least on par with a 347.

That Tremec transmission is a good choice for pulling and crawling. I stuck with the ZF5, , which is very similar.

For lift, you will need the 2" body lift to clear the R2.8. I still had to modify the hood to make it fit.

Final thoughts: The R2.8 modernizes a lot of things that most people spend weekends upgrading on the Windsor block engines (serp drive, modern electronic controls, cooling system, etc) Reliability is big factor. No matter how hard I worked on the 351W, certain aspects seem to undercut my efforts. The design is more than 50 years old. Engines have come a long ways since then. Aftermarket parts are another Achilles heal. I had issues with multiple aftermarket parts that sent the truck back to the garage. I've been in that industry and like it or not, the aftermarket does not build to the quality level of the OEMs. Add in the push to move manufacturing to "low cost regions", aka China and part quality falls further. Beyond fuel mileage and saving money, driving range was a huge consideration. I would rather go 400-500 miles between stops vs 250. Now I don't have to add Jerry cans to my bumper for long trips. That is safer than 10 gal of gas sitting on the bumper in an accident. (also diesel is not nearly as flammable)

I've talk to other owners with similar rigs (CJs, Broncos, D90s) and they all love the R2.8. Can't wait to finish mine.

 

[73azbronco]

Is the 2.8 turbo?

 

[BroncoManSam]

I've been down this road. My rig started out with a decent carb'd 351W, 375HP/400+lbft. When I first bought the Bronco, it made a whopping 9-10 mpg with questionable driveability. (poor cold starts, warm up, fueling control over rpm range) Made lots of power and burned lots of gas. With the OE 12 gal tank, I was filling up every 100 miles. ?:?

I changed cam, exhaust, intake and added a homebrewed TBI injection system. Driveability went way up, mileage climbed to 14mpg. Plugs showed the engine was running much cleaner. Switched to a 23 gal tank, but driving range was around 230 miles. Better, but not on par with current production vehicles. It got worse when towing.

Around this time Cummins re-tuned the R2.8 and bumped torque to 310 lbft. RPM and weight are comparable to a V8. Since I live in CO, mountain driving and altitude power loss are very real. Minus 15-30% hp and torque. This makes the R2.8 on par with the V8 power under certain, but critical conditions. (10,000ft passes) I pulled the trigger. The R2.8 is priced decent for what you get and ROI over the V8 is pretty good with the mileage improvements.

Here are the plus's of the diesel over the V8
- Brand new engine, alternator, PS pump , etc. All new
- Cummins reliability
- Very complete package. Computer, wiring, gas pedal, gauge, very good install manual
- Turbo power!

Here are the drawbacks:
- The Cummins takes a lot of ancillary equipment. Intercooler, PS reservoir, coolant expansion tank, remote oil and fuel filters, extra plumbing, etc The Bronco engine bay is small and it's hard to fit this all in. (Although I've figured most of this out, so skim my thread for ideas)
- Cummins will require frame mods. I had to make new engine mounts and modify the crossmember. There may be clearance issues with std width front axles. The oil pan is wider than a Windsor block. (With full widths, clearance is not really an issue and the pan doesn't hang down as far.)
- You will be largely on your own figuring out problems. Cummins has decent engine support, but no help with the rest of the integration. The RepowerOwners website is okay, but far from great for support.


For gearing, don't go deeper than 4.10s with 35s. I ran 4.56s and 37s with the V8 and will continue running them with the R2.8. There is an RPM calculator on the Cummins website. With my setup and for 4.10s/35s, you will be well into the diesel's power band. You will be beyond the optimal efficiency range. Remember that engine torque peaks at 1800 rpm.

Since I mentioned it, be careful comparing power and torque numbers between gas and diesel engines, they don't tell the whole story. My 7.3l diesel is old and only make around 190hp, but it would out-pull that 375hp V8 all day. Why? Diesel make much more drivable power. V8s with performance cams push peak torque up between 3500 and 4500 rpm. This is hardly where you want to be hanging out when towing or climbing a long grade. Diesel typically peak below 2000 rpm. Below 3500rpm, I bet the 2.8 feels more powerful or at least on par with a 347.

That Tremec transmission is a good choice for pulling and crawling. I stuck with the ZF5, , which is very similar.

For lift, you will need the 2" body lift to clear the R2.8. I still had to modify the hood to make it fit.

Final thoughts: The R2.8 modernizes a lot of things that most people spend weekends upgrading on the Windsor block engines (serp drive, modern electronic controls, cooling system, etc) Reliability is big factor. No matter how hard I worked on the 351W, certain aspects seem to undercut my efforts. The design is more than 50 years old. Engines have come a long ways since then. Aftermarket parts are another Achilles heal. I had issues with multiple aftermarket parts that sent the truck back to the garage. I've been in that industry and like it or not, the aftermarket does not build to the quality level of the OEMs. Add in the push to move manufacturing to "low cost regions", aka China and part quality falls further. Beyond fuel mileage and saving money, driving range was a huge consideration. I would rather go 400-500 miles between stops vs 250. Now I don't have to add Jerry cans to my bumper for long trips. That is safer than 10 gal of gas sitting on the bumper in an accident. (also diesel is not nearly as flammable)

I've talk to other owners with similar rigs (CJs, Broncos, D90s) and they all love the R2.8. Can't wait to finish mine.

Thanks for the comprehensive reply and all the info. I was really pleased to hear your experience especially, rather than people guessing how the R2.8 performs in off-road applications. I’d thought about going to full-width axles anyway, so if I go the diesel route I’ll definitely go with full width. Also, I imagine fabricating or modifying the cross-member won’t be the worst issue in the world; I’m doing a full, body-off-frame resto. I’ll calculate the gears again, I’ve been using grimjeeper but I’ll also check out the one on the Cummins site. Also, someone had mentioned in another Bronco group I’m in, about part availability being low for the R2.8, but if it’s as reliable as I’m hearing, I don’t imagine that will be an issue, and maybe as time goes on, Cummins will improve the R2.8, add parts and perhaps more tunes for it. I’ll definitely check out your thread for some ideas, thanks again for the info.


Sent from my iPhone using Tapatalk

 

[BroncoManSam]

Is the 2.8 turbo?

Yes, it is, as far as I’m aware.


Sent from my iPhone using Tapatalk

 

[73azbronco]

The R2.8 is 100% new.
A 347 starts with a used engine and is rebuilt. Unless you go with an aftermarket block but your build level is now where near needing the support of an aftermarket block.

For my 347 I prefer to say built vs rebuilt, nothing in mine is what it was when it rolled off the line, So it was built to be the 347. And used blocks are "cured". Now, a 347 and 351 can be poorly done for sure, because they are the ultimate shade tree mech rebuild with simple tools, thuis making the new off the shelf 2.8 and coyote desirable.

I remember when cutting holes in the hump for a different tranny was blasphemy. Now you can stretch or cut out a frame to make it work. I wouldn't, but go for it, have fun.

Last thought, I test drove a new Cummins diesel Ram and gas 5.7 Ram. I wanted the Cummins. But the Diesel was horribly rough, shifted as though it had a shift kit, mileage to gallons cost/used was not that great a difference, had no seat of the pants difference in power except the 5.7 easily out accelerated the diesel and sounded way way better, but the killer was all the tech needed to make the diesel work; filters, fluids, etc. 5.7 needed? Gas.

 

[ame]

My biggest hesitation with the Cummins is looking at all the fab work people like Digger556 is having to do, I have access to a full machine shop, laser , press brake and what not but if an engine swap requires 500+ hours of fabrication time the chances of my Bronco getting pushed into a corner and collecting even more dust is all too high. Hoping a company makes a kit with all the needed hard parts then a guide of what body and frame modifications are needed.

 

[BroncoManSam]

My biggest hesitation with the Cummins is looking at all the fab work people like Digger556 is having to do, I have access to a full machine shop, laser , press brake and what not but if an engine swap requires 500+ hours of fabrication time the chances of my Bronco getting pushed into a corner and collecting even more dust is all too high. Hoping a company makes a kit with all the needed hard parts then a guide of what body and frame modifications are needed.

That's a fair concern, especially for someone like me who has little fabrication knowledge, tools, or skills. I'm currently working with my local off-road and machine shop to plan my Bronco's full body-off-frame resto, so there'll be lots of work ahead of us anyway, so I'm hoping with the help of Digger556's build thread, I can get past the R&D segment and right into the build, if I end up going the diesel route, that is. My Bronco has been sitting in a shop for over a year, almost 2, with no work being done on it because of a part mix-up, and a 15-month delay on a body tub, so any kind of progress I can make happen is good. Looks like I might be able to get started this January, and maybe even get a body tub much much sooner. Just have to plan everything out... I have a positive inclination that Cummins will continue to improve the R2.8, as well as add parts and more tunes. Just by judging the popularity of the engine in recent years, and seeing the repower builds at SEMA and on the internet, I think the R2.8 will have an interesting future, hopefully.

 

[Broncobowsher]

There are plenty of non-machining ways of doing most of that work. But when you have the tools and the skills, you tend to use them.

 

[BroncoManSam]

There are plenty of non-machining ways of doing most of that work. But when you have the tools and the skills, you tend to use them.

I’d imagine so. I think with the help of my local offroad shop that’s doing most of the build for my Bronco anyway, I’ll be alright.


Sent from my iPhone using Tapatalk

 

[blubuckaroo]

Wow...
Once I considered putting the LS motor from my Camaro into the Bronco. I got a severe reaction from this group.
I guess diesel engines are different.?:?

 

[BroncoManSam]

Wow...
Once I considered putting the LS motor from my Camaro into the Bronco. I got a severe reaction from this group.
I guess diesel engines are different.?:?

You do you man, I think most Bronco/Ford guys have an aversion to GM powerplants, but to each their own. I’m sure there’s plenty of Broncos out there with LS engines, as there are a fair amount of diesel Broncos too. I just like the sound of this new crate Cummins, and from what I hearing from other builds, it’s a great engine. Plus, I think everyone loves diesel power.


Sent from my iPhone using Tapatalk