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Discussion Starter · #1 ·
Ok, so I have a few questions on building the next stage for my Dakota. As of right now its heavily built bottum end 360. I'm in the neighborhood of 370rhp. Now, I'm about to PCS overseas and will be leaving my Dakota with a good friend thats also a builder. I'm going to have him re-work the entire thing, all the drivetrain.

So, my main overall questions are in relation to HP to MPG. I know thats almost an oxymoron in terms of performance. But, I'm not looking for a 10sec truck here. A nice high 11 or even 12s is fine for me. I also would like to make it reliable and drivieable. Thats the kicker. When i return home I may want to make this my permanent driver. So, the questions boils down to is what to do.

I know some people are doing the HEMI swaps and getting HP and MPG and reliable, and a buttload of aggravation in the process. I have the top end already so I'm thinking I can stick to this route and build a 408. but how reliable can a 408 be if driven daily? Better yet what about mileage? My truck already gets 7mpg on premium.

I know some do the 727 swap, that to me can't help mpg. What I'm looking for is at least 10/11 with a nicely built 12 sec running 408 stroker. I have the 4:56 gears too. So I ask the experts, can this be done? 400ish RHP, reliability, 12ish quarter is wanted, daily driven, and maybe 10 MPG?

I know their are a ton of motor experts out there; I'd love to hear from them. I'm no where near an expert on motor building, just know enough to get me in trouble. Funny thing is I can work on multi million dollar military jets...go figure. Anyways, comments requested please.
 

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i get about 10 mpg average with my setup in my sig and i dd it in the summer with no problems
 

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Only way to get the power and economy is dropping in an 05 and later Durango or 06 and later Ram HEMI. They come with the MDS and if you are good with throttle control, you could probably see better than 18 mpg hwy or average, depending on your route.
There is someone out there that will be looking for a built 360, even mildly used. The point I am getting across is that the 5.9 is not designed for today's economic climate, it was designed in the early 90's when gas was less than a dollar a gallon. The MDS HEMI's are your only option for power and economy.
 

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Discussion Starter · #4 ·
i get about 10 mpg average with my setup in my sig and i dd it in the summer with no problems
You and I have very similiar mods (minus the stroked part). I honestly think part of my problem is the tune (B&G). But nonetheless, my truck has ran very well in some time and with the 5 year time span, my buddy will have the time to pull everything and rebuild it to my specs. But, even babying the truck, I've never gotten above 8.3mpg.

Only way to get the power and economy is dropping in an 05 and later Durango or 06 and later Ram HEMI. They come with the MDS and if you are good with throttle control, you could probably see better than 18 mpg hwy or average, depending on your route.
There is someone out there that will be looking for a built 360, even mildly used. The point I am getting across is that the 5.9 is not designed for today's economic climate, it was designed in the early 90's when gas was less than a dollar a gallon. The MDS HEMI's are your only option for power and economy.
While you make some since in that logic, I drive a 2008 Ram and the gas mileage in it sucks balls. I get on average 13 mpg. Thats 5 better than my modified Dakota with the almighty MDS software. trust me, in trucks-MDS sucks and was the biggest fkin scam in the world.
But, back to the Hemi thoughts...I can drop an 03-04 hemi in the truck yes. I would gain power and reliability and mpg, yes. Only problem I have with all this is I already have MOST mods I need for a 408 that will suffice for what I want, I hope. Finding a junkyard pulled motor/transmission is just asking for problems. Not to mention all the fabbing and crap thats required. I think I'll stick with the 408 idea, but thanks.
 

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here's a few pro's/con's to your questions
theres nothing exotic about 408's,they could be used in everyday life.its just more stroke and would make even a good truck engine.its the cam/heads/rpm that make it turn big horsepower numbers.
on the other hand,putting that long of a stroke in a magnum series block causes excessive wear to the cylinder walls,and getting 100,000 miles out of the block,just might be IMPOSSIBLE.
superchargers/turbo's were designed to give you fuel mileage friendly horsepower.its an on demand application,when you want more power just push the gas pedal down even further causing it to make more boost.more boost equals more power,while still giving you the option to putt around town almost in a no boost mode.
you could do the hemi swap,but i think you would be disappointed at the performance of it in the factory configuration and would start to modifying it immediently,and when will that stop.as horsepower go up-MPG go down.
if i had a magic wand (unlimited checkbook),i would install a blower friendly camshaft on the mild side,a supercharger w/intercooler and a 6-speed manual trans.that should get you back around 11-13 MPG and still be able to turn high 12's,while keeping your shortblock and 4.56 gears.
 

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Discussion Starter · #6 ·
here's a few pro's/con's to your questions
theres nothing exotic about 408's,they could be used in everyday life.its just more stroke and would make even a good truck engine.its the cam/heads/rpm that make it turn big horsepower numbers.
on the other hand,putting that long of a stroke in a magnum series block causes excessive wear to the cylinder walls,and getting 100,000 miles out of the block,just might be IMPOSSIBLE.
superchargers/turbo's were designed to give you fuel mileage friendly horsepower.its an on demand application,when you want more power just push the gas pedal down even further causing it to make more boost.more boost equals more power,while still giving you the option to putt around town almost in a no boost mode.
you could do the hemi swap,but i think you would be disappointed at the performance of it in the factory configuration and would start to modifying it immediently,and when will that stop.as horsepower go up-MPG go down.
if i had a magic wand (unlimited checkbook),i would install a blower friendly camshaft on the mild side,a supercharger w/intercooler and a 6-speed manual trans.that should get you back around 11-13 MPG and still be able to turn high 12's,while keeping your shortblock and 4.56 gears.
All makes since. make no mistake, I'm up for any option. I just think since I have the top end already (heads, cam, intake, etc) it would be just a basic shortblock swap (more or less). A hemi motor would required a shit ton of modifying, plus require bolt ons to get descent power from it. 100k miles wasn't what I had in mind. But if I wanted to drive an hour up the road, I'd like to rest assured I could make it. Right now i sweat just driving 17 miles to work if I wanted. I'm not against radical thinking. I'll be more than happy going back to 3.92 gears too, but the cam doesn't like factory gears.

So...the question remains how to get 350- 400rhp and be drive-able and reliable. There has to be a way to get above single digit MPG.
 

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my average is about 10mpg. i have around 370-400ish at the wheels(havent dynoed it yet but my times are good). i dd mine in the summer and i never have any real problems with anything. always starts and runs great. superchargers and turbos are awesome and if i had the money i would buy a supercharger, but since you are 3/4 of the way there you might as well stroke it and be done. forced induction is probably less reliable because you run the risk of burning a piston. just my thoughts. i wanna supercharge mine but i have a secondary vehicle if i burn a piston.
 

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just call john...
 

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Discussion Starter · #10 ·
just call john...
You know, your starting to act like some of the other guys around here. I asked for advice, clear cut and simple. Not everyone can build a 408, fabricate lines and install a manual shifter, add methanol and a blower. I know what John would say. Maybe I want something more streetable and not so track heavy.

Now if you don't have any pertinent information to add, please see your way out of the thread. Thanks.
 

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Discussion Starter · #11 ·
my average is about 10mpg. i have around 370-400ish at the wheels(havent dynoed it yet but my times are good). i dd mine in the summer and i never have any real problems with anything. always starts and runs great. superchargers and turbos are awesome and if i had the money i would buy a supercharger, but since you are 3/4 of the way there you might as well stroke it and be done. forced induction is probably less reliable because you run the risk of burning a piston. just my thoughts. i wanna supercharge mine but i have a secondary vehicle if i burn a piston.
I was thinking this as well. A nicely built 408 with a "proper tune" might give me exactly what i want. I know most go with SCT, but I may go the DFI route to tune via stand-alone.
 

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You know, your starting to act like some of the other guys around here. I asked for advice, clear cut and simple. Not everyone can build a 408, fabricate lines and install a manual shifter, add methanol and a blower. I know what John would say. Maybe I want something more streetable and not so track heavy.

Now if you don't have any pertinent information to add, please see your way out of the thread. Thanks.
I dont think he will be too happy when you tell him how to build the engine. You spoke highly of him so he should be able to build whatever you want.

a little bit of usefull info... Unless you dont have emissions dfi will not let you be street legal and to be honest its an over kill if you just want a 12 sec truck.
 

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Discussion Starter · #13 ·
I dont think he will be too happy when you tell him how to build the engine. You spoke highly of him so he should be able to build whatever you want.

a little bit of usefull info... Unless you dont have emissions dfi will not let you be street legal and to be honest its an over kill if you just want a 12 sec truck.
I appreciate your help and knowledge. John will build what I want, yes, but I wanted inputs from people like yourself on which route I should go for what I wanted out of the truck. Knowing John like I do, he would really enjoy building some monstrous rat motor, carbed, with a 727 bolted in and dump the pcm altogether to bypass its limitations.
Judging from the basis of replies, and since I have most of the ingrediants already, it seems logical to have him build me a 408, but keeping my transmission. I don't know much on SCT but isn't it limited as well based on the o2 readings? It seems alot of people have had success with this tuner so I may go this route as well. Just saying.
I have 4-5 years to complete this and by then who knows what will be out. I'm going to have my extremely skilled friend work this stuff for me in his shop. He normally builds track monsters...and chevy's. So, hmm working on a Mopar will be new for him. I'm leaning heavily towards a well built 408 and a good tune. I think thats my problem right now. My truck is running on a B&G tune and some days it runs rough, others smooth. And it smells PIG PIG PIG rich even on the dyno shows it slightly rich. Talk about STINK! And 7mpg is retard-ville, IMO.
My truck needs alittle work anyways. Seems most my hardware on the motor is rusting now. So, I want all that shit replaced with SS pieces. All braided lines as well. Maybe move the battery to the back. And I am seriously considering swapping headers. I just don't feel these things are worth it anymore. So, alot of little things he can do in the mean time.
Thanks for the information.
 

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arent you running the southeast longtubes? my overhead console showed me getting 14 mpg on the highway on my way to the strip. dont know how accurate that is.
 

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maybe thats the problem, you listened to john's bs for too long.


back to the topic, i get 14-15 mpg out of my heads n cam 360 and 17-18 on the interstate, which happened the last time i came down to charleston. i did daily drive it til it got cold and it has no heater considerin the heater core went out. i say build a simple motor and it be safe for n2o, when you want power just spray it, with n2o it can be runnin 11s or 12s w/o borin n strokin.


also u been gone to much/long, flashed ecu's are crap now and sct is the 2nd best next to stand alone bein 1st option, with sct u buy it, something to monitor a/f-tps-etc and sean powell to program it and itll run like it just got programmed from a dyno
 

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Discussion Starter · #16 ·
arent you running the southeast longtubes? my overhead console showed me getting 14 mpg on the highway on my way to the strip. dont know how accurate that is.
Yes. Truck has never gotten anything above 9mpg once the heads/cam/gears went in. More-than-likely its the tune.

maybe thats the problem, you listened to john's bs for too long.


back to the topic, i get 14-15 mpg out of my heads n cam 360 and 17-18 on the interstate, which happened the last time i came down to charleston. i did daily drive it til it got cold and it has no heater considerin the heater core went out. i say build a simple motor and it be safe for n2o, when you want power just spray it, with n2o it can be runnin 11s or 12s w/o borin n strokin.


also u been gone to much/long, flashed ecu's are crap now and sct is the 2nd best next to stand alone bein 1st option, with sct u buy it, something to monitor a/f-tps-etc and sean powell to program it and itll run like it just got programmed from a dyno
So much hate for John lately, wow. Never once had a problem with the guy. Anyways, yeah your probably right. Build the motor, SCT it, add a bottle for whenever and enjoy. Probably be the way I end up going. The B&G flash has always ran the truck quite rich anyways and probably is effecting performance and mileage.
 

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Go ahead and buy the SCT now with unlimited tunes. Your MPG will go up no doubt. Sounds like a terrible tune and you are probably eating 02 senors.

My advise, build a solid 360 for a FI, either supercharge it or turbo charge it. You want the power all the time I am assuming. You can put a mild cam in it. I run a 216 cam and drive-ability is still very good. No need to go 408 to reach the 11's and defiantly not the 12's. What upper half do you have already?
 

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Discussion Starter · #19 ·
Go ahead and buy the SCT now with unlimited tunes. Your MPG will go up no doubt. Sounds like a terrible tune and you are probably eating 02 senors.

My advise, build a solid 360 for a FI, either supercharge it or turbo charge it. You want the power all the time I am assuming. You can put a mild cam in it. I run a 216 cam and drive-ability is still very good. No need to go 408 to reach the 11's and defiantly not the 12's. What upper half do you have already?
Mods currently: .020 Mopar block, Custom grind cam with PHAT duration, SouthEast RT port & polished 2.02 heads, 1.7 adjustable RR, 4 bbl M1, 1000 CFM single blade TB, S&S LT headers, B&G tune, 8.8 wires, true duals, 2 core BeCool radiator, .600 springs. Thats the majority of the motor. The bottum end is untouched except what came with the shortblock. I do know I have a few cylinders low on compression right now but I think thats mainly my fault for adjusting the RR too tight.
 

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Mods currently: .020 Mopar block, Custom grind cam with PHAT duration, SouthEast RT port & polished 2.02 heads, 1.7 adjustable RR, 4 bbl M1, 1000 CFM single blade TB, S&S LT headers, B&G tune, 8.8 wires, true duals, 2 core BeCool radiator, .600 springs. Thats the majority of the motor. The bottum end is untouched except what came with the shortblock. I do know I have a few cylinders low on compression right now but I think thats mainly my fault for adjusting the RR too tight.
You should be in the 12's with that if you have a big cam. I had less and than that and ran 13.27's and still got about 13mpg. Get Hemifever to retune it and get a good datalogger. I think you will be surprised where you are right now. No need to change anything just yet. Except maybe building up a better block. You might be able to do a high CR block and run the number you want NA.
 
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