OK, a little background. I'm a former 15 year Mopar parts guy (98-12). Been around cars my whole life, dad and stepdad were techs. I really like the new hemi. Drove them a bunch at the dealer, my father in law has an 05 1500 2wd that we have put 110,000 on. Nothing but fluids and plugs for maintenance. It gets 18 mpg on his trips to Chicago and Denver from San Diego. I figure I can get 15 in my 79 Ramcharger. I'm getting 10-12 from a carbed 360 magnum with a Hughes HER0814 cam, Eddy 650avs on a M1dp. 4.56 gears, 33s and a nv4500 5spd. It's got part-time axles out of an 83. After getting 11mpg overall on a 1600 mile trip to Moab and back, NY wife is asking me to look at the costs of adding efi to the magnum vs a hemi swap. Yeah, I know such a hard choice to be forced on me.

So, it has to be CA legal which means all emissions junk. I can add obd1 now for minimal cost, already have most of it. How much better is obd2? More tunable right? That would cost me about $1500 to do right. Realistic mileage with efi on my 360 is 13-14 at best. My 95 1500 4x4 auto, 33s and 3.55s got 14. Heavier but better areo. The real unknown is how good can I do with the hemi? I do a lot if 300+mile trips for camping and wheeling. So it matters. Opinions?

I think the first thing I would do is get rid of the 4.56 gear..

I would think 15 is about as good as your going to get pushing that pile of bricks through the air with the big aggressive tires, regardless of what is under the hood. It takes a certain level of power to move that mass through the air, and power consumes fuel. Smaller all season radial tires, a more road friendly gear ratio, and devices to smooth the air flow might gain you a few more mpg, but I think your about at your limit without radical changes. There is a cost to having fun, in your case, its fuel mileage (and probably a few broken parts along the way). Gene

Concidered that. 4.10s may be better. But I'm going to 35s on the next set of tires and figured I leave the 4.56s for now. With 33s I turn 2200 at 65 MPH. 4.10s would drop it to just under 2000. Part of my problem is the truck easily goes faster. 80 MPH speed limits in UT. Even though it's easily do 80, anything over 70 really starts dropping the mileage on this thing. Aerodynamic it isn't. But it is lighter than the newer trucks. Fully loaded with all our gear, full tank and my wife and I it weighs 5600#.

Yeah 80 MPH with 4.56 gears I think you did really good to avg 10 mpg.... FWIW I have never seen a 360 get any kind of mpg at all. Everyone I have had was a total gas hog... Can't say for certain but I would think the HEMI would probably get better than the 360 but for that kind of money you could probably swap in a Cummins 4Cyl or 6cyl and problem would be solved...

Read up on OBDII and the CA emissions regs.
You CAN swap in a later model engine, BUT you must retain ALL the equipment.
EVAP, downstream O2 sensors, etc. The biggies will be wiring, fuel tank and evap, and getting all the gauges to work right, since a Hemi is all CAN BUS driven. Don't forget the throttle by wire as you get toward the home stretch!

Would it be legal to swap in a Cummins 4bt???

I don't think you'll do any better with a 5.7 than an EFI 5.9. I have an 05 ram 1500 4wd quad cab. It's got 3.92 gears and 275/60/20's, about 33" tall, and it probably weighs in the 5500 lbs with me in it. The best I can get is 19 mpg ish if everything is perfect and I'm doing 60 mph on the nose, kick it up to 70 mph and its 15 mpg. Only modifications are shorty headers, magnaflow y pipe and Flowmaster cat back.

I'm a big fan of the 5.7 but given the challenges of California emissions I would stick with what you have. If you do go with EFI get a custom tune, the stock tune is awful.
Aren't vehicles over 25 yrs old exempt from emissions testing?

I understand the emissions issues. As to the 4bt, from what I've read it can't go in a light duty truck. They were only available in medium duty delivery trucks and construction equipment. But, I have seen a YJ Wrangler running around with one. Saw it at a local car show but never got to talk to the owner. Some guys swear there is a way around the regs but I haven't found one yet.

As to hemi vs 360, the hemi will get better MPG everyday. A stock 360 at least. I have a Hughes HER0814 cam. Adding headers and 1993 mpfi to start. Later I will go to obd2 from a 96-00 and add a Hughes Eddy Airgap efi and sct tune. Or the hemi. The cost of all the parts to upgrade the 360 will nearly be as much as a good used hemi. That's the big question that I don't know the answer to. The magnum maxed out or a hemi, which would be the better one for what I'm using my truck for.

big iron ram look that name up on the board. he has a ramcharger about the same vintage with a 5.7 in it.
you can ask him some specifics.

but either way, it seems more expensive right now to add a hemi over a 5.9 mag still, when retaining the efi.

unless you manage to get a complete donor cheap for either one, the stuff to make the hemi work is more expensive.

Also I recall him showing me a place he notched in the frame so the exahust would clear for the hemi. not sure if that is a problem for you or not.

Another advantage to the Hemi is about 100 horsepower over the Magnum.

How about a Hemi with an aftermarket fuel injection like FAST or Holley.

The thing with your 5.9 is you've fixed the thing that makes it bad on fuel, the crappy ignition timing. If you really want a 5.7 then just take the plunge, but it's not going to be cheaper but it is a better motor

those magnum, keg style intakes do not like rpm's for efficiency. About 1800-2000 is about were it needs to be to get fuel economy. 2200/2300 ish rpm, fuel economy drops of quick.Maybe an aftermarket intake is better? I have no idea. I've had a few ramchargers. 77 360 2 bbl,82 360 4 bbl,93 318 magnum. 10 -11 mpg is all they ever got. my 2000 quad cab Dodge dakota with 360, auto 3.91 gears and 31 inch tires. all factory and stock.10.6 mpg is my overall average. My over head console w fuel economy shows about 16mpg's at 45 mph, 70 mph is about 11/12 that is around 2300 rpm.

The 5.7L is going to make way more power and get better mileage than a smog legal 360 will hands down. Really improving the efficiency of the 360 while remaining smog compliant is going to take alot of work and you will still be compromised by the emissions rules. The hemi will probably have a higher upfront cost but don't be scared off of the project by the emissions certification, its not that hard to do.

-Jon

I'm doing 6.1 swap now, same cost for swap other than the extra cost of a 6.1... let me say first hand, it's not cheap! There's probably as much money in swap parts as the 6.1 costs.

If I were doing a 5.7 swap into a truck, I'd use the dash and as much as I could from a donor vehicle. The computer/wiring is a big cost part of the swap.

that's the rub, smog legal. I have all the stuff to go obd1. but i lived in NV in a non smog county when i built this magnum. the cam isn't that big but is on a 112 LSA. i'm waiting to hear back from Dave at Hughes for his opinion on my cam and obd1. damn thing runs great, just want more mileage and to be smog legal. it's a pain going up to NV just for vehicle registration. most everyone i knew has moved away too.

i wouldn't even be thinking about the hemi if i could swap a 4bt in. two guys i know that did it (not CA)love it, 20+mpg. the nearest smog ref is 40 mi away, just gotta go down and talk to him. too many ideas, not enough info to make a decision. thanks everyone, i'll let you know what the ref says.

74 -older are exempt.

Hello from Hawthorne Dave.
I had the 05 5.7 hemi in a 3/4 ton 4x4 with 33 inch tires. I couldn't get more than 15mpg at 70. With 4.56 37bfgs non o/d trans, in my 84 R/C and a old raggedy 360 I can barely get 70mph lol that's not entirely true. But my mileage at 70 and 3200 rpm is a dismal 8mpg if I slow to 55 its 14 mpg. I swear that the old 360s have more bottom end grunt but the hemi well its a rever 6000 6300rpm is where the computer would shift when carrying or pulling a load.
The 360s, magnum included just don't have the compression the hemi has nor do they have the gifted cylinder head. The cams that come in the magnum and the pre magnum just run out of efficiency at higher rpm. So in my mind the difficulty is keeping the bottom end grunt and getting some upper RPM efficiency with the 360s. Which I think can be gained in compression, cam and a head that flows well.
The Hemis also seem to be gifted with a better transmission, lower geared in first and quick shifting. It may have been the computer limiting torque but it just seemed revy not torquey.
This is all just food for thought, My mind doing what it does SQUIRREL. Good luck on your endeavor.