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11:56:23 - 04/29/2024
V6 Dakotas
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Christenson
Dodge Dakota
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10/01/2004
17:02:17
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 Subject: Magnum heads on pre-mag block?
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I have an '89 dakota and am tired of the lack of guts and poor gas mileage. I was reading in Mopar Muscle of how they put magnum heads and intake on a pre-magnum 318. I was wondering if that could be done on the 3.9? Would I have to change anything else or could I simply swap the intake and heads? I would like to increase performance and thought that this might be an easy way to go. If I'm dreaming just let me know. Thanks.
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vern
Dodge Dakota
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10/01/2004
19:27:39
| RE: Magnum heads on pre-mag block?
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i did,nt see the MM article,but yes the mag
heads will bolt on the pre mag v6s,you,ll need the push rods and valve covers too,
now here is where the differents lay,if you use the mag intake,its a multi-port injection,you,ll
need the pcm and wiring harness,and tb,
i,m not sure on this maybe the dist to fire the injectors
but you can use your pre mag intake on the mag heads by having the heads drilled and tapped at a machine shop or you may be able to do this yourself,this i know for sure,i,ve done this myself and you use everything you have now,
its easier and cheaper,heads,covers,push rods and some gaskets,drill and tap heads for intake,
install on your motor
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gen1dak
Dodge Dakota
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10/01/2004
19:52:29
| RE: Magnum heads on pre-mag block?
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Like Vern said, yes, but there is an alternative. Try to find these heads first:P4452747
These are the best pre-Magnum heads for the 3.9, and the ports are less than 5cfm variance from the Magnum. Much of what was developed in these heads was transferred to the Magnums. If you can find these, all your existing hardware will transfer over since it's physically an LA head. The V8 heads are still sold by Mopar, but the V6 units aren't as numerous. If you can find them you'll save yourself a lot of swap work and money. They're good for a 30hp increase on an otherwise stock 3.9, naturally, with a cam, even more. This info comes straight from my 1990 Mopar Performance catalog.
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Christenson
Dodge Dakota
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10/01/2004
21:06:16
| RE: Magnum heads on pre-mag block?
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Thanks for the responses. The article in MM was in the Sept. '04 issue. They were building a 318 that would produce 400hp with very little machining, just bolt it up and go.
I'm not much of a mechanic and even less of an electrician so if you could help me a little more that would be great. If I were to take the heads, push rods, intake and everything above that (throttle body, wires, etc) that should about do it with the exception of the pcm and wiring harness? Could you help me identify where the pcm is located exactly and what wires I would need?
After doing all of this and installing it correctly, everything should work good on my truck even after replacing the pcm? I simply don't know what controls what with the new computers and electronics so I want to make sure I have my bases covered before I dive in. Thanks.
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gen1dak
Dodge Dakota
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10/02/2004
10:09:02
| RE: Magnum heads on pre-mag block?
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The article cited is a bit easier than what you're looking at. Your idea is certainly do-able, though more complicated with OEM electronics being involved.
If you're going to use the full Magnum setup, you will also need the crank sensor. On Magnum engines, at the rear of the engine, on the passenger side, right behind the cylinder head, there are two raised bosses where the sensor is mounted. You will also need a Magnum era flex plate (for automatic) or flywheel (for a stick) because they have a built-in ring with notches which the sensor reads. You will also need to notch the tranny bellhousing for the sensor to peek through. There's one notch for each cylinder. This tells the PCM where each cylinder is, and is necessary for proper injector and ignition control. Otherwise, I suppose you could adapt an MSD-style crank trigger to the system, which operates on the same principle.
Keep in mind that adding Magnum heads will also net an instant increase in camshaft specs. The Magnum rocker ratio is 1.6:1. The preMag LA is 1.52:1. The ,373 intake and .4 lift numbers are changed to .39 and .42 inches, which can only help, thought the Magnum V6 had .432 lift on both intake and exhaust. Anyway, it just means you'll have a little more cam to take advantage of the better heads, but a Magnum-era cam would boost it even more.
It is absolutely vital that you make sure you use hollow pushrods, and make sure they lifters in your engine are oilers, meaning they have a small hole in the pushrod cup for the oil to run through, travel up the pushrod, through the hole in the rocker arm (all Magnums have these) to lube the upper valvetrain. My '89 318 has these, so most likely, you do too. Mopar did a lot of this stuff in transition phases, long before it was necessary----LA's oiled the valvetrain via holes in the cam journals, that allowed oil to travel through the block, up to the cylinder heads to the rocker shafts. The Magnum block and heads are not drilled for this, so their only oil supply is via the lifters and pushrods. When you bolt the heads on, the gaskets will effectively block off your LA block oil passages, so no worries there.
The PCM on an '89 is a black box on the passenger-side fender. It'll have lots of wires running into it.
One problem with swapping Magnum heads onto an engine, and using the MPI is that the Magnum heads have no exhaust crossover passages in the heads, as on LA's. Using the MPI setup pretty much dictates you'll have to use the Magnum intake manifold as well. The intakes were EGR units through 1995.....1996 and up were non-EGR, OBDII electronics, and you don't want that much pain, so avoid them for this buildup. The 1995 and earlier units were OBDI units, and are much easier to work with. EGR was handled with the crossovers on the LA engines, but on Magnums, it's handled with an EGR tube that fits to the rear of the intake manifold, and ties into the passenger-side exhaust manifold...so you'll need a set of those too. Say goodbye to your air-injection system. You won't need it anymore. PreMag 3.9 and 5.2's used one air pump, 5.9's used 2....OBDI Magnum 3.9 and 5.2 were able to eliminate that, and the 5.9 needed only one.
Now, for an engine harness, I've been lucky there. I snagged a full 318 Dak harness for under $30 on eBay, so keep your eyes open. PCM's show up occasionally too. Get a PCM that matches the V6 requirement, and tranny (overdrive auto or stick).
You really should get a factory service manual for your truck, as well as one for a 1992-1995 Dakota. Helps a ton. Got both of mine on eBay as well for $30-$40 each. It's all in there, you just have to read it. Be prepared to do research in the manuals. This isn't gonna come together in a weekend.
Okay, for fuel, you're gonna need more pressure, so dropping in a Magnum-era pump is the easiest way there, though there are external pumps available.
Of course, snagging a Magnum V6/V8 pull from a wreck is looking pretty good right about now, huh? It'll bolt right in, and have all the goods, all it needs is the better fuel pressure, electric fans, and some power for the PCM....tranny might not live long with the extra power, but that's an issue with your build-up as well. Dang magazine articles never mention all the details!!!
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Christenson
Dodge Dakota
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10/02/2004
20:08:47
| RE: Magnum heads on pre-mag block?
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gen1dak, thanks for the honest, up-front replies to my questions. I appreciate you being real about what is involved with switching the heads, intake, etc. The MM article makes it seem like you can get the heads, intake and some wiring/electronics and you're ready to go. Oh how I wish it were that easy!
After considering all that you have told me I have to put the kabosh on this project. I am in college and was hoping to up the MPG on my dakota as the trip to school is about 7 hours and the dakota as of right now isn't too nice on gas. I guess the lesson is that I should've studied up and saved some more pennies and bought a magnum equiped dakota.
Since I hope you'll read this I must ask you one more question even though the head swap is no longer within the realm of possibility. What are the best (if there are any) ways of increasing the MPG on my first generation dakota? Any help would be great. Again, thanks for your honest and detailed replies.
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vern
Dodge Dakota
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10/03/2004
18:45:53
| RE: Magnum heads on pre-mag block?
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set the timing to 12-13 degrees instead of 10degrees,install a electric fan and a good tune-up plug wires,plugs,cap and rotor button[copper contacts]if its been awhile,high voltage coil
[msd,jacobs etc]make a good coil
cost about $200-250
these things will help power and mileage
also have the o2 checked to see if its working properly,this alone can hurt mileage big time
hope these help
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gen1dak
Dodge Dakota
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10/03/2004
20:08:28
| RE: Magnum heads on pre-mag block?
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Along the lines of what Vern said, but there are always other routes as well.
Remembering my days of worrying about being stranded, I'd never disable my engine-driven fan, even if I could gain a little mileage. I had a '69 Charger with a hopped-up 318 that routinely managed 18 mpg, and it had the factory-style viscous-drive fan. My '89 Shelby Dakota, despite 20-years difference, was basically the same package. Despite all the technology, the Shelby never, ever got better than 16 mpg, and the Charger would run rings around it. The dual electric fans in the Shelby drew so much power you could feel the load every time they kicked in, and the altenator strained to feed them. Once, a relay fused, and they wouldn't shut off until they were unplugged, which made them useless. I ripped them out, and squeezed a different radiator in, along with an aftermarket flex fan (only because there's not enough room for the viscous-drive fan clutch). To me, the electric fan gains aren't worth the chance of failure. Granted, they've come a long way, and they're in stores now, much easier to get, but my flex fan will never burn out. It's a trade-off I prefer.
You can bump up the initial timing with a twist of the distributor, the PCM handles the rest, but if you advance it too far, it'll rattle, and you either have to turn it back some, or run higher grade gas. You could probably sneak in a bit of initial, as stated, around 12 degrees. Anything to relieve the choke points helps. Keep a clean air filter, or step up to a K&N re-usable unit. It's a proven winner. I'd freshen up the sensors, especially the O2 and MAP sensors, and remember to pull the battery power for several minutes to reset the PCM so it'll "see" the new parts and act accordingly. Ever consider a tonneau cover, or one or those flow-through tailgates? Taller tires will give you an effective gear ratio change, which lowers the engine rpm at a given speed. It will also probably decrease acceleration a tad. Just remember to factor that in, or get a speedometer unit from Mopar to compensate, otherwise the speedo will be wrong. Before you do that, get an engine vacuum gauge and tie it into your engine. These are in JCWhitney catalogs for around $30. When cruising, drive at whatever speed generates the best engine vacuum. You must do this driving, as the results will be somewhat different than standing still due to engine loads. If your engine makes best vacuum at 80mph (in top gear), you could swap out for slightly shorter tires. This'll pull the vehicle speed down a little at the same rpm/vacuum level. A simpler, and less costly method is just to drive as close to your peak vacuum range as possible without speeding.
You could also adjust the transmission kickdown, but this is really boring. The engine upshifts sooner, downshifts later. This has the effect of getting the tranny into top gear sooner. It's un-inspiring, but it will save gas. Speaking of tranny, if an automatic, when was the last time it was serviced. This helps too.
None of this will make a dramatic change, but it's the cumulative effect that will add up. You could really benefit from a new timing chain and gears. If you have more than 50,000 miles on the current set, they're junk. They'll run a lot longer, but performance suffers. Oh, and while you're in there, put a new water pump on. Nothing worse than going in there and 2 weeks later the water pump goes out. I saw a 3 mpg improvement on my dad's RamCharger just tuning everything up and putting in new timing chain and gears, and it ran a lot better!
Finally, open up the exhaust. High-flow catalytic converter is a plus, and a decent muffler...the OEM styles are pretty restrictive.
Your coil is bound to be weak. Even an OEM replacement will help. Use quality 8mm sparkplug wires. The beauty of all this is that it can be done in stages. Sheeesh! I'm writing another book here.
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gen1dak
Dodge Dakota
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10/03/2004
20:11:03
| RE: Magnum heads on pre-mag block?
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Oh, don't forget. The MM article was for a carbureted application. That makes it MUCH easier to do the Magnum-head swap. If you still want the MPI Magnum setup, look for a complete package. There's always some hotshot wrapping one around a tree.
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jagbor
Dodge Dakota
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10/26/2004
11:28:09
| RE: Magnum heads on pre-mag block?
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Now this is interesting..........I am a Canadian living in BC and was just advised by a dodge mechanic(18 yrs experience) that if I simply installed a high lift/high duration camshaft into my 1990 3.9L a/t dakota, I could expect at least a 50 hp increase to the measely 125hp it currently puts out. Was this guy bs..ing me? Also.......gen1dak posts a mess stating that if I could find the following heads
#P4452747(does anyone still make these or am I looking at finding a wrecked magnum dakota? also-where will I find this P4452747 number?)then these should essentually just bolt right onto my existing engine and increase hp by 30-is this correct? because directly below this mess + in another one, he explains in great detail "all of the other things that need to be done IN ADDITION to just bolting on the P4452747 heads. I agree with Christensen that if ALL of these things are required to get maybe 40hp out of a truck, it just simply isn't worth the time or the money. Any thoughts?
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gen1dak
Dodge Dakota
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10/26/2004
22:45:19
| RE: Magnum heads on pre-mag block?
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jagbor, you'd do well to read my "mess" again. The details of what was required centered around Magnum head swaps. The only thing necessary for an instant 30hp increase is bolting the P4452747 heads on. The heads (P4452747), are not Magnum heads, they are LA heads, and were never offered as an OEM part, strictly aftermarket through Mopar Performance. However, since you don't believe anything I've posted here, I'm posting this for the benefit of others. As for you....go ask that so-called "experienced" mechanic how well a high lift/high duration cam will work with the computer in your Dak, and then ask him where P4452747 can be found.
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Curt
Dodge Dakota
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10/28/2004
09:56:09
|  RE: Magnum heads on pre-mag block?
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Vern,
Thanks so much for the info about placing magnum heads on a nonmag (LA) engine. I have been wondering about this mod to my 90 v-6 for quite some time and it appears that you have experince doing this. I do have a few question and was hoping maybe you could help me.
I know that the magnum heads would need to be drilled and tapped to accept my LA intake manifold but is there anything else that needs to be done? Do the ports line up OK between the two or is there some porting required to make them match. I want to keep my old TBI manifold because I don't want to go through the headaches of changing to MPI (crank sensor,computer,wiring harness etc.)
I am clear that the valve train components from the magnum will need to used. My lifters were replaced about a year ago and I installed the oiling type lifters which have the hole to oil through the push rods enventhough that is not being used at this time with my solid pushrods.
I would also like to ask if the old LA exhaust manifolds will fit the magnum heads or will I need the magnum exhaust manifols? I have a fairly new exhast system and would hate to change the Y-pipe but I would if I had to.
I also would be very interested in set of the high performance LA heads which you mentioned in your post. Where would I begin to try and locate a set of these heads for my V-6? I don't have a clue!
Thanks so much for your time and it is really good to see that there is someone on this board willing to help us old gen.1 guys!
Curt
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jagbor
Dodge Dakota
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10/28/2004
16:45:16
|  RE: Magnum heads on pre-mag block?
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Thanks gen1dak-I apologize if my message sounded like I didn't believe what you posted-I have read several of your responses and you do know alot about daks. I am genuinely interested in finding the P4452747 heads as 30hp gain would make me utterly ecstatic at this point. Did I read correctly that Mopar Performance offers these? do they have a web site? What does "LA" and OBD1 mean? What sort of cam would you recommend for my truck-2WD, ex-cab, automatic? If I am able to find the heads, is there anything else to change/upgrade after they are installed? I am not interested in peeling the tires off the truck but was recently on a camping trip thru BC where I was pulling a 1500lb trailer-on some of the steeper hills, I could only go 35mph(60km/hr) so just want a little bit more hp to help with this. Thanks again gen1dak for your knowledge & expertise.
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vern
Dodge Dakota
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10/28/2004
21:02:31
| RE: Magnum heads on pre-mag block?
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hi curt
the ports line up fine[but a good port match will help also]
the exsh. manifolds will work from your premag,so no problem there
i,m not the one who said MP made the performance
heads, gen1dak did,i,d try MP,swap meets,ebay etc
like i said earlier heads,pushrods,valve covers and drill and tap heads and gaskets,this is all
you,ll need to install
you could also mill the heads,this will up the compression a few points,for every 4-5 thousands
removed will up the compression 1 point
sample-compression 8.5,remove .015 from heads,
compression up to 8.7-8.8
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Curt
Dodge Dakota
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10/28/2004
22:13:54
| RE: Magnum heads on pre-mag block?
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Thanks for the info Vern. I will be at the local bone yard this weekend hunting some mag heads. I'll let you know how everything turns out when I am finished.
Curt
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gen1dak
Dodge Dakota
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10/28/2004
22:33:27
| RE: Magnum heads on pre-mag block?
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Okay jagbor, chalk it up to a misunderstanding, eh?
Let's see. LA refers to the smallblock Mopar engines starting with the 273 V8 in 1964. From this foundation sprouted the 3.9 V6, 318, 340, 360, 488 and 505 V10. The Magnum series started in 1992, and are essentially LA blocks with different intake and heads, which explains why Magnum heads will retrofit pre-1992 engines. You can even drill the oil passages in a Magnum block, swap in an LA cam (they have oil holes), and you can use pre-Magnum heads and intake on a Magnum block. So, Magnums are LA's too, but they're LA's with a different top-end, so typically, when LA is referenced, it means pre-Magnum.
To find the P4452747 heads, well, that's a tough one for the V6. The V8 version is still sold by Mopar Performance in three basic fully-prepared versions, but the V6 doesn't show in the more recent catalogs. Vern mentioned swap meets, and if I were looking and not in a hurry, I'd try the swap meets, and make some calls to MP and places like Manciniracing.com They might have a lead on them. There has to be some in inventory somewhere. In lieu of the P4452747 heads, I'd get the stockers reworked with mild porting (mostly cleanup) and a 3-angle valve job. Then I'd call Competition Cams and tell them I wanted a 3.9 V6 cam with their 254HR-12 grind and the 901 springs to go with it. This will greatly improve your power, but will work with all your OEM electronics. Even with stock heads, it'll help a lot, just make sure to get the springs. The stock springs would never handle it. It'll be a custom-ground cam (meaning steep $, but rollers are already more expensive anyway), since they don't list it as a regular item, but the grind is for the 318 with the same goals in mind. A little more duration, a lot more lift. Works great with your computer. The cam should offer 25ish hp (hard to say, but definitely more with better heads), since the stock cam is .373/.400, and the CC grind is .480/.480. This really perks up the mid, and especially upper rpm power. If you find the P4452747 heads in new condition, all you'd need to do would be to swap over your rockers and shafts, since, as marketed, they were outfitted with HP springs, etc, and were ready to run. They're a true bolt-on. Get the cam, keep looking for the heads, or get another set of stockers and have them reworked and ready so you can do a 1-day swap.
A Magnum head swap won't work properly with your electronics. I mean, the heads can be drilled, but they have no exhaust crossovers, so the EGR will not function (emissions testing an issue?), and it'll have bad manners in colder climates. You have to either go carb (and still have bad manners in the cold), or do a total Magnum top-end swap, as well as Magnum electronics or some sort of aftermarket controller.
OBDI:On-Board Diagnostics. Not sure just when it started, but along with the fuel-injected, computer-controlled engines. It ended with the 1995 model year, and was replaced by a much more complicated (typical, it's mandated by the feds) OBDII computer. One good thing is that OBDII did away with EGR.
And then there's the V8 swap option.......
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Curt
Dodge Dakota
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10/28/2004
22:54:55
| RE: Magnum heads on pre-mag block?
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One more question for Vern
What do you think I can expect in gains by adding the magnum heads and keeping my TBI? I do have a spare set of injectors from a 5.2 and they fit my throttle body. They deliver a little more fuel than my 3.9 injectors. They work ok now except on cold starts my idle is little rough for the first few minutes. After the engine is warm everything smooths out great. My thoughts are when it is cold the computer is in open loop and these injectors are maybe causing a rich condition. Maybe with the mag heads there will be enough extra airflow to handle the larger injectors. What are your thoughts?
Thanks again
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Boon
Dodge Dakota
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10/29/2004
01:33:23
| RE: Magnum heads on pre-mag block?
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thanx for the egr info gen1 dak.Had the heads picked out and was talking to head machine shops and emissions will matter in the near future no way around this but a v8 and $ i guess same problem as curt 9o 4x4 5 speed 3.21. Also U or Vern ever ran a spacer UNDER your tbi?
Did a homemade one on 84 ranger 2.8 v6 worth 3.5mpg with a little more power in the mid to top end forgot the eletric fan also well worth the time at a junk yard and 20$
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vern
Dodge Dakota
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10/29/2004
09:11:55
| RE: Magnum heads on pre-mag block?
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curt-i,d say in the 20-30hp range,the only real differents between the mag and the premag is the heads,little bigger cam and the multi-port,
i,ve had that same problem with the 5.2 injectors,some say you have to run them 500mi for the computer to relearn
i don,t NO worth a try
boon-i have,nt tryed the spacer,but i did port and polish my tb this helped,took the torque step out at the bottom of the bore and thinned the throttle plates shaft,notice no differents in mpg but helped over all
hughes engines.com has cams for our trucks,
there regrinds $197 exchange,but they say you have to use their valve springs with them $76,
for about $300 all,
one last thing you can do,i,ve done this on my 89 dak,roller rockers,i bought a set of used adj rockers and shafts from a 318/340/360 cut the shafts back,bought new pushrods and installed them,if you go with 1.6s instead of the 1.5s its like installing a little bigger cam,you,ll go from .373/.400 to about .400/.430 at the valve
$200-300 depending on what you buy
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gen1dak
Dodge Dakota
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10/29/2004
13:01:11
| RE: Magnum heads on pre-mag block?
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Never ran a spacer on mine, but since it's a wet intake like a carb, it'll help boost the upper end where these setups typically suffer.
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Curt
Dodge Dakota
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10/29/2004
18:18:11
| RE: Magnum heads on pre-mag block?
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Question for Gen1dak.
I noticed that egr valves are listed for 92 and 93 dakotas and they are the same part # as for my 90. The mag engine started in 92. Where is the egr valve located on the 92 and 93 dakotas?
Thanks again for the information. You and Vern are really helpful to us gen.1 guys.
Curt
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