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1st Gen Dakota '96 & Older Dakota's

3.9L performance upgrades

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Old 07-26-2012, 01:15 PM
JGC403 JGC403 is offline
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Default 3.9L performance upgrades

I'm looking to get a little more power out of the little 1989 3.9L. Engine was recently rebuilt a couple of years ago and runs strong, but needs a little more power. Since the motor was rebuilt I am starting with a decent foundation, and don't want to swap in a V8. Plus I want to see what can be done with the little V6.

Truck gets about 22-23 highway, so that's my baseline, trying to get a little more power and economy out of it. I am on a budget of $3000 for the motor.

I think I have 2 routes I can go, build up the motor and keep it NA or go force induction.

Option 1, NA build: Cam, P&P heads and intake, headers, 1.6 or 1.7 rockers, V8 TBI or convert to MPI, Under-drive pulleys, higher compression ratio.

OR

Option 2, Force induction build: remote mount turbo like Hans5.2 did. Can this be done for $3000?

Whats going to give me the most bang for my buck?
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Old 07-26-2012, 06:31 PM
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is it the magnum or the la series? if its the la i heard that no matter what you do to it it just doesnt get much power, like the magnums do. ive read this on here, maybe if you upgrade the fuel injection to mpfi
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Old 07-26-2012, 07:16 PM
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pre 92 were the la blocks...sadly
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Old 07-26-2012, 10:40 PM
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Yea mine is a LA. The LA valvetrain is better in my opinion than the magnum.

Probably going to end up going with an aftermarket PCM, like MS-II.

So other than the TBI vs MPI i don't see why there would be a problem getting power out of it.
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Old 07-26-2012, 11:31 PM
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Yea mine is a LA. The LA valvetrain is better in my opinion than the magnum.
Please tell me how stock LA is better then the Magnums.

The Magnums are LA's with factory performance parts. Higher compression heads, larger valves, larger intake and exhaust manifolds, larger exhaust pipes. Higher fuel pressure, more injectors, roller rockers with a higher ratio. Better cam. Do I have to keep on going? The list doesn't stop.


Good luck finding a cam or headers or anything for the V6 LA it was only made for 87-91, only for 4 years and only Dakotas a very very few Rams thats all. There are VERY few performance parts for the V6 Magnum which was 92-03? 10 years or more

Yes an aftermarket stand alone PCM will help a bit but not much. The LA's were low compression low performance engines due to emission regulations.

Your best bang for the buck is a V8 Magnum swap way under $1,000 for a rebuilt engine. Since you don't want to then your next best choice is a turbo setup. Depending on what deals you find yes under $3,000 is do-able. The low compression of the motor will help if you add in some good boost numbers from the turbo. But then you might have to add in larger injectors and fuel pump and the stand alone PCM to advance timing a good amount and control the injectors.
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Old 07-27-2012, 12:19 AM
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Please tell me how stock LA is better then the Magnums.

The Magnums are LA's with factory performance parts. Higher compression heads, larger valves, larger intake and exhaust manifolds, larger exhaust pipes. Higher fuel pressure, more injectors, roller rockers with a higher ratio. Better cam. Do I have to keep on going? The list doesn't stop.
From what I found the compression ratio didn't change between the LA and the magnum V6. The exhaust manifolds are smaller on the magnums. The rocker arms are not roller in either engine, but the magnum is 1.6 ratio. There are roller lifters in both.

The shaft mounted rockers are more stable in the LA than the pedestal mounted Magnum setup. I'm not saying the LA is better than the Magnum, the Magnum is a newer design so its going to have some advantages over the LA. I was saying the LA has a better valvetrain.

Camshaft from a Magnum motor will fit the LA block. Hughes Engines has camshafts.

Swapping in a V8 snowballs into a lot bigger project and more money. Once I have the engine, the transmission would need to be upgraded, then to clear the transmission tunnel I would need to do a 2" body lift, and a new driveshaft.

Anyways either engine could be built up. Talked to my Uncle (who I'm building it for) just refreshed everything with new gaskets and rings. I thought it was at the machine shop and been bored out, but it hasn't. So the block is going to take a trip to the machine shop.

Last edited by JGC403; 07-27-2012 at 12:33 AM..
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Old 07-27-2012, 05:59 AM
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If your going to tear the motor back down to get bored out throw in some forged goodies and put it on the bottle. Like Crazy said there isn't alot of performance parts for your engine so turbo, sc, nitrous is about the best options for adding a large amount of power.
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Old 07-27-2012, 11:57 AM
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Quote:
Originally Posted by JGC403 View Post
The exhaust manifolds are smaller on the magnums.
The 92-93 manifolds are way bigger the the others.

Quote:
Originally Posted by JGC403 View Post
The shaft mounted rockers are more stable in the LA than the pedestal mounted Magnum setup.
It doesn't matter when you can't push more then 100HP.

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Originally Posted by JGC403 View Post
Camshaft from a Magnum motor will fit the LA block. Hughes Engines has camshafts.
Fit yes work no the oiling of the cams are different. www.allpar.com has all the details.

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Originally Posted by JGC403 View Post
Swapping in a V8 snowballs into a lot bigger project and more money. Once I have the engine, the transmission would need to be upgraded, then to clear the transmission tunnel I would need to do a 2" body lift, and a new driveshaft.
Transmission yes will need to be upgraded. A few others have gotten away with using the V6 trans on the V8's. But I don't recommend it for to long. The transmission tunnel is the exact same from 87-96 with the V8's to the 4cly. No modification necessary. The magnums have the same motor mount locations as the LA's. It is a direct drop in swap. The only issue on pre 91's is the V8 with the engine driven fan will not fit. An electric fan is needed. The Shelby Dakota's was proof of all that.
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Old 07-27-2012, 12:30 PM
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nice, i knew crazy would have all the facts
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Old 07-27-2012, 04:14 PM
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Fit yes work no the oiling of the cams are different. www.allpar.com has all the details.

Yes, since the valvetrain gets oiling trough the block in the LA engine there is a hole in one of the cam journals for oil to get up top. The magnums use through the push rod oiling and don't need this hole in the cam journal.

Called Hughes engines and since all of the V6 cams are reground cores anyways, I could send mine it and get it reground. So I can get an R/T cam for the V6 LA for $199.

I thought I read someone need a 2" body lift to fit the transmission. This truck has a manual transmission.

Last edited by JGC403; 07-27-2012 at 04:19 PM..
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Old 07-27-2012, 04:14 PM
 
 
 
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