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1st Gen Dakota '96 & Older Dakota's

3.9L engine rebiuld

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  #1  
Old 11-19-2011, 04:36 PM
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Default 3.9L engine rebiuld

Im 16 and own a 1989 dodge Dakota 2wd auto 3.9L and the engine runs fine but needs a tune up and all the gaskets replaced but while its out (which i need help on the removal part) i would like to slightly rebuild it and make it look good so what do you guys suggest replacing and is it worth it to rebuild it it is my first truck and it means alot to me and would like to hit 1 million miles with it, it only has 128,000 so i got awhile
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  #2  
Old 11-19-2011, 09:52 PM
bill55az bill55az is offline
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Why are you pulling the motor? Modern engines are lasting a lot longer than the old days....
Had a machine shop tell me that the heads need work at around 125,000 miles and then they are good to go for another 100,000 miles.
but if you are pulling it because some inaccesible seals leak, then by all means replace freeze plugs, tranny front seal, motor front and rear seals, oil pan gasket, etc. There aren't a lot of performance parts for the v6 but if you want it to feel like it has a v8, look into the rear axle ratio. You most likely have the 3.55 ratio, and a 3.92 will be an improvement in driving fun without costing a lot in increased gas consumption.
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Old 11-19-2011, 10:02 PM
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thanks and yeah i think the engine is leaking oil out the main seal and the trans is leaking out the front
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Old 11-19-2011, 10:20 PM
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do a compression check, if all 6 cylinders are good, don't rebuild the engine....just take care of all the leaks.

If a cylinders has low compression, squirt some oil into the spark plug hole and test again. If the pressure remains low, look into a valve job on the heads.. if the pressure goes up, piston rings are likely in need of replacement.

Find out exactly what is broke before tearing into it....saves a lot of headaches...
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Old 11-20-2011, 07:41 AM
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do you have to have the engine in the truck to do the compression test or an you do it while its out the engine also has somewhat of a knock and tick i also plan on doing a whole gasket and seal replacement new bearings main and rod also ale guide seals and also rings but if it dont need rings that would make it easier but would they go bad later
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Old 11-20-2011, 09:34 AM
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a compression test requires cranking the motor with a pressure gage stuck in the spark plug hole, so yes. If there is a knock, different ball game.
Before rebuilding this motor, look into buying a used one from a reputable junk yard.
The newer v6, from 92 to 2003, are MUCH better engines....problem here, tho, is the intake manifold. There are none for Throttle Body fuel Injection for the magnum v6. THere are maybe a dozen made to be used for carb or TBI with adapter plate. I had one of the few, and I sold mine a few months ago.
The v6 just isn't that popular an engine so performance parts are not available...
The best bet is to drop in a 5.2 magnum v8. There are carburetor intake manifolds for them that you can put an adapter plate on top of, and use your TBI. The 89 Shelby dakota had a LA version of the 5.2, and it used the v6 front springs, so this is an easy way to get serious horsepower in your truck. There won't be room for a fan blade so you will have to put an electric fan in front of your radiator/condensor. DOes it have air conditioning?
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Old 11-20-2011, 10:10 AM
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well i don't really are for more power i just want a reliable engine it doesn't really have a knock it is more like a tick im thinking of getting the re ring kit that comes with gasket and seal kit rod and main bearings and rings its like $200 from rock-auto i don't really want a v8 because its expensive and then i would need a new trans and then it would get complicated
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Old 11-20-2011, 10:25 AM
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The tick could just be your timing chain.
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Old 11-20-2011, 10:27 AM
bill55az bill55az is offline
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If just a tic, that is probably in the valve train, and a valve job on the heads is a good idea. Is the truck still in one piece? Make sure the tic isn't the oil dip stick getting hit by the crankshaft. Just lift the dipstick an inch while the engine is idling. I have seen that before.
The v8 will get almost the same gas mileage, USES THE SAME TRANNY, and performance parts are plentiful....for later on.
Last time I will say this, make sure you know what is NEEDED before tearing into it....
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Last edited by bill55az; 11-20-2011 at 10:29 AM..
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Old 11-20-2011, 10:38 AM
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Quote:
Originally Posted by hogback View Post
well i don't really are for more power i just want a reliable engine it doesn't really have a knock it is more like a tick im thinking of getting the re ring kit that comes with gasket and seal kit rod and main bearings and rings its like $200 from rock-auto i don't really want a v8 because its expensive and then i would need a new trans and then it would get complicated
I understand the complication aspect, that is why I have been offering the least compllicated path, or paths, to take. Rebuilding an engine gets very expensive, there is only so much you can do yourself, and the machine shops are not cheap.
You can use the same tranny, same motor mounts (if you use a magnum v8), same radiator, same TBI (with larger injectors), and probably the same computer, altho I am not sure of that last part. But they aren't that expensive.
My 89 came with a 4 banger, so I needed a lot of different stuff. Yours can be easy, if you listen to the more experienced members here...
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  #11  
Old 11-20-2011, 12:10 PM
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how much would a v8 cost i would be interested but i dont have much money at all like i could over all spend $300 so it would have to be very cheap

Last edited by hogback; 11-20-2011 at 12:15 PM..
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Old 11-20-2011, 04:22 PM
bill55az bill55az is offline
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better save some more money, rebuilding your old one will cost a lot more than that. The heads alone will set you back that much....
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Old 11-20-2011, 04:38 PM
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i don't plan on doing anything to the heads i am just doing a re ring kit including rings valve stem seals gasket set and rod and main bearings no machining just a tune up of sorts but i am up to any suggestions on cheap performance parts ideas
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Old 11-20-2011, 05:02 PM
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without a compression test, you don't know yet what needs the most attention....
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  #15  
Old 11-20-2011, 06:41 PM
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i might do a compression test i can borrow a tester from my teacher and when i tear it apart i can borrow a cylinder hone also
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Old 11-21-2011, 08:58 PM
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im also thinking throttle body spacer straight piped duels no glass pack or cats and i will sell them and the a homemade cold air intake also heavier valve springs and used roller rockers
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Old 11-21-2011, 10:15 PM
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do you have the LA? throttle body do nothing for the magnum engines but not so sure for the LA's, i would save your money and use it for something else
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Old 11-21-2011, 11:03 PM
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I am going to make a suggestion, maybe 3.
Figure out what is wrong FIRST.
Find out what your budget is FIRST.
Don't listen to old school hot rodders when building for a modern vehicle.

People on this sight know just about everything about these vehicles and how to mod them for best performance, listen to them, don't listen to "Buck" in the garage who builds chvy 350's, drops them in a POS nova and tells you to do a bunch of stuff that isn't applicable to a modern vehicle, especially a magnum Mopar engine.

You seem to be on the right track but don't let your exuberance get in your way, otherwise your budget is shot and you have a partially working vehicle. Everyone over the age of 30 and is into cars knows exactly what I am talking about.

Get your heads done. You will get more power and efficiency out of them and you will not have to worry about them for a long time. They most likely need welded in between the runners, it's common, cheap, and the fix lasts a lot longer than factory. Not only fixed but a good port and polish job, get them to flow.
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Old 11-21-2011, 11:26 PM
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Quote:
Originally Posted by hogback View Post
im also thinking throttle body spacer straight piped duels no glass pack or cats and i will sell them and the a homemade cold air intake also heavier valve springs and used roller rockers
throttle body spacers are worthless, save your money....

It is illegal to run without catalytic converter, and no mufflers at all is not good for the engine and it will attract the ticket writers.

you don't need heavier valve springs unless you want to stress your valve train...

the 89 v6 alreadly has roller lifter valve train...

you gots lots of reading to do before tearing into that truck, lots....
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Old 11-22-2011, 06:26 AM
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i know i need to read that's why im on there and that's why i suggested those things so i could see what you guys think. But I dont have a big budget so why would i get my heads done when then i would have a non running truck with good heads that is still leaking.

the reason i am doing this rebuild is that it is leaking out the rear main seal and that means it has to come out so i though i should replace all the gaskets while i have the chance then i ran into the re ring kit and i was fascinated and i want to do that because i like engines

I dont work nor do i get money from anything so i cant just do one thing wait till i get the money and then do another it would take 10 years so i cant do anything major
Any suggestions are still welcome and donations for your guys expensive fixes are also welcome
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Old 11-22-2011, 06:26 AM
 
 
 
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