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Custom Dodge Ram Performance Mods - Engine - 3.9 Liter V6 Discuss modifying your Dodge Ram with Performance Parts and Accessories!


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  #11  
Old 01-26-2019, 02:47 AM
Gen1dak Gen1dak is offline
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OK, so it looks like you're going with the '89. The V6 system was pretty rigid, leaving little overhead for power increases. The V6 and 318 TBI were the same system, but any power ups then involved putting the 360 TBI and computer on the smaller engines. The 360 TBI would be hard-pressed to adequately meet the higher output Magnum, with absolutely no room for cam swaps and other power adders. Basically, what early Magnum swappers did was to take an older vehicle and use the engine computer/harness to run the basics. The Magnum is multi-point, not batch fire. The TBI computer will not run the Magnum. If you're doing the whole HVAC deal, a little wiring shouldn't be too bad. You can graft the Magnun engine computer into the '89's system, letting it manage the engine/drivetrain/AC/voltage, and whatever left can be handled by the stock computer, or, I have no doubt those remaining systems can be spliced in. Might as well swap the dash so the gauges will work with the Magnum computer too. Usually, most would take a simpler approach and just carb it, but the full smash can be done. They're the same truck, essentially. Having a donor truck makes it so much easier. Houston, huh? Been doing that biz lately. Can't stand it! Really need some punch to work the gaps.
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  #12  
Old 01-26-2019, 07:51 AM
Avian Auto Avian Auto is offline
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Vehicle: 1989 D-150
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Engine: 1988-1991 239ci (3.9L) LA V6 125hp
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The 3.9 engine was a hurry-up project of Chrysler to modernize and upgrade from the 225 slant six. With a very limited budget, Chrysler put the 3.9L into production and had difficulties from day one. The fuel system that is on my truck was used only either 2 or 3 years, then the fuel management was upgraded to port fuel injection that was, I believe sequential. Also, I'm not sure, but I think a balance shaft was added to cure the idle "wiggles" like my truck does. This 3.9 stayed in production until it was replaced by the Mercedes design-inspired 3.7L in about 2002 or so. the 318 was replaced by the also Mercedes-design inspired 4.7L that remained in production until about 2012. My 2002 Ram 1500 has that 4.7L... it is a very good engine design.
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  #13  
Old 01-26-2019, 11:20 PM
Gen1dak Gen1dak is offline
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The 3.9 was a rush job, with the goal of using it in existing production lines, with existing tooling and parts, because, at the time, they had nothing between the 2.5 and the 5.2. The TBI was used a total of 5 years between the 3.9/5.2/5.9. Despite the jumpy nature, especially noticeable with a standard transmission, it lasted 13 years.

Last edited by Gen1dak; 01-27-2019 at 01:22 PM.
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  #14  
Old 01-27-2019, 09:36 AM
Avian Auto Avian Auto is offline
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GM's TBI system had "jumpy" issues too. We fixed that by putting small capacitors across each injector at the connector. This stabilized the peak hold injector. It was never officially recognized, and probably embarrassing for such a simple, dirt cheap fix to be figured out by an aftermarket engineer. I've cured many TBI systems over the years doing this.
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  #15  
Old 01-27-2019, 01:30 PM
Gen1dak Gen1dak is offline
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The 3.9 jumpiness was due to the odd way 2 cylinder were removed from the 318. They essentially lopped off 1/2 of the cylinders on one end, and 1/2 from the other end, then off set the crank on the new center. The whole arrangement created an out-of-balance engine with an odd firing sequence. They sold some of it by splitting the crank pins, but it wasn't something that could be dealt with by adding weight like conventional external balancing. They had an odd fire issue with the V10 too, but with more firing pulses per rotation, it was less noticable. A little vibration isn't a big deal. It's more about asthetics. Just look at Harley V twins.
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  #16  
Old 01-27-2019, 04:29 PM
Avian Auto Avian Auto is offline
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I mis-interpreted "Jumpy". I think of that characteristic of V-6 engines without counterbalance shaft as a quiver. When GM made the first generation of the Buick 3.8L V-6, it quivered just like my D-150 does. They split the crank pins and went to even-fire from odd-fire and greatly improved it, but it still had the problem. Eventually they engineered a counterbalance shaft and used that engine in the Buick Grand National... and it was stupid fast.
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  #17  
Old 01-31-2019, 05:06 PM
Gen1dak Gen1dak is offline
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Man did I have come typos last post. Anyway, they didn't bother with internal counter-balancing on the 3.9, but they had a fine one on the 2.5 turbo, (so good, in fact, it was Motor Tren or some magazine like that, that complimented it by asking, "Are you listening GM?") although one of the first more-power mods is to remove the counter balance for a quick 20hp or so.
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  #18  
Old 01-31-2019, 06:43 PM
Avian Auto Avian Auto is offline
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I flat don't accept that a counterbalance shaft takes anything more than very minimum power to turn.... certainly no where near 20 HP... Matter of fact, I'd believe the reduction of vibration would enhance power.
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  #19  
Old 03-22-2019, 09:48 PM
Gen1dak Gen1dak is offline
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I wasn't sure exactly what the number was, but it appears to be 10-14hp depending on the engine.
http://www.thedodgegarage.com/turbo_oil_pump.html
It was also in a Mopar magazine from back in the day. That's where I remember it from. Think about it. Mass requires energy to move. Why do you think derious racers will spend thousands of dollars for exotic lightweight engine parts (think valve train) for a few ounces or maybe only a few grams of weight savings? It adds up.
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