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
