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Engine swap question

niceolddart

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I have a super nice, low mileage 2000 V8 Dakota with the NP3500 transmission. I was thinking building a 360 Magnum engine to replace the current 4.7 V8. I thought about building a 3G HEMI for it, but it's just WAY more than I want to spend & more work that want to do since I'll be doing it myself. (If I decide to do it) Has anyone done this? The 4.7 is a good runner but I would like to build a pretty stout 360, roughly 400 H.P. or so. First, will the Magnum bolt right in if I use the correct engine brackets? Will the NV3500 bolt right up to the engine & also still be in the same location? (I'd like to use the stock driveshaft) Will the factory ECU & wiring work on the Magnum engine without too much modification? It is the first year for the 4.7 in a Dakota, so I don't think too much is different, but I'm not sure. It's a lot of work for me at 63 & I'll be doing it in my driveway to boot. I'm I asking for trouble? Should I just get a tuner (SCT) & a set of 4:10 gears for it & run the 4.7? I was told the tuner & 4:10 gears would wake the 4.7 up quite a bit. I'd like some of the in-put you all can offer. I know a lot of you don't like the 4.7 because of some supposed problems, but I've heard of people getting well over 100,000 miles out of them, with no problems if they are taken care of. Anyway, what say you?
Thanks all.
 
I would say if it's running ok leave well enough alone and go by an old beater to mess with.
 
Yep, still runs great, It'll get rubber in 3 gears pretty easy & never had any trouble with it, except sometimes I have to charge the battery because it may sit in my shed for a couple months. The thing only has 51,000 miles on it.
I already have an old beater, a 73 Duster, but want to get rid of it though. getting too old to mess with 4 cars/trucks. (All Mopars by the way)
 
You are thinking too much you have a good truck as it is If you want to build a 360 do it. I had one in the corner of my garage for several years and finally found a place for it in a 64 Dart GT from California 4 speed with a rod out of the side of the slant 6 and that thing really ran with the v-8 it went through Mecum for $38,000
 
You're probably right MILO. I should just leave well enough alone & hop-up the 4.7 that's in it.
 
IF yur getting rubber in 3 gears, why hop it up?
The 4.7 is too small for a truck in the first place; that's just 287 measly cubes.
How much does that truck weigh? Supercharge it or leave it be.
 
IF yur getting rubber in 3 gears, why hop it up?
The 4.7 is too small for a truck in the first place; that's just 287 measly cubes.
How much does that truck weigh? Supercharge it or leave it be.
I did weigh it once, & I think I was around 35-3600lbs. I have been looking at some mods recently to it that are pretty cheap & not too difficult to do. Mainly intake, cams, stuff like that, from a 2008 & up 4.7s that had a lot more H.P. from the factory, over 300. I know a lot of Mopar guys (That's ALL I own) are not fans of the 4.7 & I think it get a lot of bad press, but it seems like a pretty good engine so far, just maintain them. I do wish it had the 5.2 or 5.9 Magnum engine though, they are MUCH easier to get hop-up parts for. We'll see what I can coax out of the original 4.7 I guess. Probably do the 4:10 gears to start & see how that goes.
 
Don't get me wrong, I like the SOHC 4.7 design, I really do.
And 235 net hp is pretty doggone strong for the displacement.
In the Jeep it rose to 265 net, a heck of a thing. That is likely to compare to 312hp crank, which is early 340LA territory.

I'm guessing you realize that;
> cams just increase an engines ability to breath at higher rpm, if the top end supports it, and they do it by trading away power off the bottom right? and,
> with no other changes, the only way to get the bottom end back, is to rev the engine up higher, right? and
>What you end up with is a powerband that starts later and ends later in both rpm and mph.
> To get the power back at lower speeds, then requires a bigger rear gear. which increases the Cruise rpm.
> starting with just 4700cc, it's gonna take a lotta cam to make appreciable power, which is gonna steal a lotta bottom end away, requiring a lotta more rpm off the line, to overcome.

>If your truck is as light as you say; and it probably already has 3.91s, and so, 4.10s are only 4.8% bigger, which will hardly be noticed.
IMO
as to engine performance, in that Dakota, your options are;
a bigger engine, or
a super/turbocharger, or
leave it be.
The usual engine starting point is 10 pounds per cubic inch. Thus your 287/4.7 is good to 2870 pounds with you in it and half a tank of gas.
At say 3700/you in it, you need to start with a 370/5.9
Only a supercharger will give your 4.7 the off the line grunt you may be looking for, simultaneously with power throughout the powerband. But if she is already spinning the tires in three gears, then you don't need more engine. What you need first, is to solve the traction issues. Until then, more power will only create more tirespin.
The usual way to stop the tirespin in a truck, are ladder-bars/coil-over shocks; with CalTrac/Assassin bars/floating leafsprings, as a close second; and of course, appropriate tires and shocks..
Of course, that changes the personality of the truck, from a nice street truck to a point and shoot straightliner.
So the Performance aspect is morphing.
To keep the trucks current personality, is gonna be tricky. Ima thinking to start with custom aluminum-alloy, slapper bars, and a soft-loc clutch. Cuz w/o the soft loc, that 3500 might just disintegrate. It's already running on the max input torque of 300 ftlbs.
The gear ratios in that box, most likely, are;
3.49-2.14-1.38-1.00-.73od. The 5.9 makes that 300ftlbs likely by 3000rpm, so not the best choice trans for behind a 5.9 NOR a supercharger. So Ima thinking a turbo is a better idea.
However, a turbo and a clutch is also not the best thing for that transmission, especially after you fix the traction issues.
What you really need is a A518 with ratios of
2.45-1.45-1.00-.69od and a loc-up, and a rear gear swap, and THEN, a 5.9 .. Now yur about as bulletproof as it gets, with an automatic.

If you really want a stick, you'd need the A833/Commando with a GVod for cruising. This is also about as bulletproof as it gets with a manual trans. The ratios would be
3.09-1.92-1.40-1.00-.78od. Compare that to the NV3500 at
3.49-2.14-1.38-1.00-.73od.
Now you can put just about anything in front of that A833, no soft-loc clutch, even a stroker and a supercharger, and Anything in the back;
and so, until you fix the traction issues, get tirespin to 80/90 mph.
Is that what you want?

I did a lil detective work with the Wallace calculator.
Your current 4.7, if it is operating at say 800 ft elevation, it should be making about 158psi cylinder pressure, for about 235 hp@4400rpm..
Lets bump the power up to 5000rpm. that's 600 rpm higher and will require a cam about three sizes bigger.
The stocker is 244/254, and IDK the LSA so I'm guessing at 112. The Ica on the factory cam is thus ~52* . That's a pretty small cam. Lets go with a custom cam of 262/270/108. In at 106, that will get you an Ica of 57*
The pressure falls to 152psi from 158, and the P/V changes from 116 to 108, losing you 7% bottom-end performance, which will require 7% more rear gear, and probably 600rpm more rpm at take-off, so you-know, like a Mustang.

So, your cost goes from a cam kit, Plus probably bigger injectors, to plus gears, plus installs, plus reprogramming, and a cold-air intake system would be a great idea. So yur looking at how much? Up here in Canada, my guess is about $3000>3500C
And the hp increase, at 5000 rpm, I'm getting 32hp. Making your cost about $100 per horspower.
Is that what you want?

Don't get me wrong, I like the SOHC 4.7 design, I really do. and 235 net hp is pretty good. But if it was mine, I'd leave it alone except for a massive pressure increase and a cold air kit. I mean your alloy heads should be able to support 200psi still on 87E10, which compared to 158 is plus 26.6%.. To get 200psi, the Scr would need to be increased, (with the stock cam) to 11/1 an increase of nearly 2 full points
That will get you ~25hp alone without any of the side effects. and a massive bottom end increase predicted to be to 147V/P compared to the 114 of the current set up; an increase of 29%. That's like supercharging!
Well there is one side effect Your torque is also gonna jump up massively a similar 29%, which is then possibly 29% more than the NV is rated to...... so it's likely gonna grenade itself pretty quick, at WOT.

If you study your Dakota pkg, you will soon see that the powertrain is absolutely NOT overbuilt. All the parts are well-matched in stock configuration.

IMO, the most likely way for the trans to survive is a well designed turbo system.

Happy HotRodding
 
Your points are well taken. The truck does have an H.D. 3:55 geared 9-1/4" Trac-Lok rear from the factory. I did build a cold air system for it & a cat back single exhaust. (I never liked dual tail pipes unless they were real duals from the manifolds back) I will probably go with 4:10 gears & an SCT tuner for now. I want to keep the manual transmission because I like shifting gears on my own, plus it's pretty rare to find a V8 Dakota with a stick shift. It IS fun to drive & handles really good too!
 
and 235/75-15s?
that would be like 65= 1960 rpm, with the 3.55s.
4.10s would increase that by 15.5% to 2265, still acceptable, IMO.
I get pretty good fuel-economy at 65=2240.
4.10s are like a half a gear. That will really help those wide NV3500 splits, from Third gear and on.
In my 430 hp car, the best Second Road-gear ratio(MT) turned out to be a 6.82 with 27" tires. But I have gobs of torque. This gets me to 65=5500, on a power-peak of ~5200.
Your current Second-Roadgear combo is 3.55x2.14=7.60 for 65=5750 in Second on a power-peak of 4400, or in third at 65=3700 in third;
so, one is too high and the other is too low.
The right gear for 90.7" tires, with your 4400+200=4600 shift-rpm, is 6.08, for 65=4600. The closest you can get, is a 6.08/1.38= 4.40 gear in Third. This is about half way between 4.30 and 4.56..
The 4.30s will get you 65=4490, while
the 4.56s would be 4760.
4.30s would cruise at ~65 = 2375, so that's the one I would chose for 235/75-15s.. Three gears to 65 would be pretty cool except
First gear is now 4.30 x 3.49= 15/1, which, corrected to a 27" tire so I can understand it, is still 14/1 which is ridiculously deep. You'll be out three lengths and already looking for Second. If you had a traction aider, so you could actually go WOT without tirespin, this could be a good thing. But without, all you get at WOT is tiresmoke. and if you short-shift, then you'll be in the stinking 61%, 1-2 split; ( 2.14/3.49=.613). So then, if you shift at 4400, the Rs will drop to 2700, and there you are wheezing yur way outta that hole. That ain't performance.
And if you go into Second still spinning, well spinning ain't winning.
Ima thinking, with 4.30s, First gear will end up being a parade gear, and you'll be launching in Second most of the time...... Like I did.
The 2-3 split is a lil better, outshifting Second at 4400, will get you 2840; so you'll want to stay in Second to say 4800, coming into third at 3100.
IMO, yur gonna need more cylinder pressure. But only if you can get the tires to stop spinning.
I would build me some custom aluminum slapper bars post haste, lol. I mean, it's so easy/so cheap. Why aluminum? Cuz the steel ones are heavy, and you'll feel their weight over every speed-bump and thru every pothole. If your 4.7 is already spinning into third gear I would do this before I did anything.
If you can get 4.30s to hook, three gears to 65mph will make your 4.7, about the quickest one around, even in stock trim.
The only things I would do to the engine, are
1) make sure it can go to 5000rpm reliably, which with a SOHC should be cake. and
2) make sure it neither detonates, nor goes lean, nor runs out of oil.
Oh and if you have variable valve-timing, you may have to study that out a bit.
 
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and 235/75-15s?
that would be like 65= 1960 rpm, with the 3.55s.
4.10s would increase that by 15.5% to 2265, still acceptable, IMO.
I get pretty good fuel-economy at 65=2240.
4.10s are like a half a gear. That will really help those wide NV3500 splits, from Third gear and on.
In my 430 hp car, the best Second Road-gear ratio(MT) turned out to be a 6.82 with 27" tires. But I have gobs of torque. This gets me to 65=5500, on a power-peak of ~5200.
Your current Second-Roadgear combo is 3.55x2.14=7.60 for 65=5750 in Second on a power-peak of 4400, or in third at 65=3700 in third;
so, one is too high and the other is too low.
The right gear for 90.7" tires, with your 4400+200=4600 shift-rpm, is 6.08, for 65=4600. The closest you can get, is a 6.08/1.38= 4.40 gear in Third. This is about half way between 4.30 and 4.56..
The 4.30s will get you 65=4490, while
the 4.56s would be 4760.
4.30s would cruise at ~65 = 2375, so that's the one I would chose for 235/75-15s.. Three gears to 65 would be pretty cool except
First gear is now 4.30 x 3.49= 15/1, which, corrected to a 27" tire so I can understand it, is still 14/1 which is ridiculously deep. You'll be out three lengths and already looking for Second. If you had a traction aider, so you could actually go WOT without tirespin, this could be a good thing. But without, all you get at WOT is tiresmoke. and if you short-shift, then you'll be in the stinking 61%, 1-2 split; ( 2.14/3.49=.613). So then, if you shift at 4400, the Rs will drop to 2700, and there you are wheezing yur way outta that hole. That ain't performance.
And if you go into Second still spinning, well spinning ain't winning.
Ima thinking, with 4.30s, First gear will end up being a parade gear, and you'll be launching in Second most of the time...... Like I did.
The 2-3 split is a lil better, outshifting Second at 4400, will get you 2840; so you'll want to stay in Second to say 4800, coming into third at 3100.
IMO, yur gonna need more cylinder pressure. But only if you can get the tires to stop spinning.
I would build me some custom aluminum slapper bars post haste, lol. I mean, it's so easy/so cheap. Why aluminum? Cuz the steel ones are heavy, and you'll feel their weight over every speed-bump and thru every pothole. If your 4.7 is already spinning into third gear I would do this before I did anything.
If you can get 4.30s to hook, three gears to 65mph will make your 4.7, about the quickest one around, even in stock trim.
The only things I would do to the engine, are
1) make sure it can go to 5000rpm reliably, which with a SOHC should be cake. and
2) make sure it neither detonates, nor goes lean, nor runs out of oil.
Oh and if you have variable valve-timing, you may have to study that out a bit.
I get what you're saying but, I'm not trying to make a race truck out of this thing, just a little more powerful street rod. It only has 51,000 miles on it. I don't drive it too much & I don't want to do to many alterations to it. I do have 275/60-15s out back & 255/60-15s up front. It will get rubber in the first 3 gears, but that's fun stuff to me.
 
I'm sorry man;
I just don't get it.
That your engine already gets rubber in three gears, clearly indicates that your engine already has a preponderance of power, but for some reason you want more. What's the point?
I'm just gonna take my dumb azz down the road.
Happy HotRodding.
 
I too would like to know if a Magnum motor will bolt into the place of a 4.7 if the proper mounts are used. I have a 2004 Quad cab 2WD truck with a 4.7/545RFE. Someday, when the 4.7 gives up, I would like to swap in a 5.9 Magnum and 46RE transmission. I may junk around and see if I can find a Dakota or Durango that's a few years older, but same gen as mine, with a Magnum motor so I can pilfer wiring and gauges, plus motor mounts. I can't imagine Chrysler would have made frames with different frame saddles for different style motors? I bought my truck in 2018 with a locked up 4.7 (imagine that?) for about nothing. It has fought me with every bolt I have turned, but I really like it and want to keep it. I installed a remanned 4.7, which has not given me the first problem other than having to replace a water pump. Heater cores in these trucks suck to replace! Thought I'd piggy back in this thread and revive it to see if anyone has info on motor mounts for the swap. Happy Thanksgiving.
 
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