Team, I'm new to this forum so thank you in advance for helping. I have a decision to make. My son (who is 17) is taking an old W100 4x4 I had sitting around and decided to revive it. It originally had a slant 6 but was converted to a 318 many years ago. That 318 is about dead. He purchased a running 94 5.2 magnum from a Dakota with the intentions of replacing the 318. He got all the electronics, wiring harness, and fuel system from the Dakota to help the conversion. Before installing, I recommended we tear the magnum down to inspect it. He did and it needs a complete rebuilding. Block is fine, Cam is bad. Crank is fine. My question at this stage is whether to spend time/money rebuilding the old engine (which we have not torn down yet) or continue with the magnum? It seems to me the advantages of the magnum is fuel injection (and maybe one or two more) but the disadvantages are we have to do the electronics, wiring, & fuel conversion. If we stick with the old style, I feel we need a 4 barrel intake and carb (as opposed to the original 2 barrel it came with). That's a new intake and carb cost on top of a rebuild. And probably a newer distributor and ignition system. I would appreciate any thoughts for carbureted vs Magnum approach. Pretty soon, I'll be making decisions about machining, cam, pistons, etc so I could use the advise.

 

Welcome Mark,
Sounds like you just need to decided if you are going to go EFI or Carburated ? You are rite, The long road is switching to EFI. It is a nice switch as long as the Budget is there to see the project though? Thats just a choice you have to make!
Both are a good way to go in my book. Only thing I would suggest.... Put some compression in them and a good torq cam for the 4X4...

Keep us posted.... Great Father Son Project.... Keeping the old Dog in the family !!!

 

There's nothing wrong with learning mechanics with the old school ways first. Of course I am assuming that you are going to be working on this with your son. you could rebuild the original 318, add electronic ignition, better cam and a four barrel carb or an aftermarket EFI and get close to the magnum in performance and economy or just rebuild the magnum.
Good luck either way you go there are pitfalls both ways.

 

I have always loved the idea of a Magnum swap but it’s a taaaaad above my paygrade, methinks. I’m a decent basic shadetree mechanic type but I dunno much about the comp systems and harnesses and the like. If it were me, and I had the ability, no doubt the newer mill would find its way between those frame rails.

 

Hey Racerhog - thanks for the note. Yes, its a Carburated vs EFI decision. The Carburated approach is straight forward except I will need to replace the Intake and Carb. The original Carb is a pain in the butt and never wants to start very well. I've worked on it till I'm blue in the face and then I replaced it - but still a pain. I'm not going to spend any more time on it - that's why if I go Carburated, I will go 4 barrel. Before my son purchased the junkyard magnum, I would have gone that direction. I was willing to help him do the magnum swap even though its a pain (EFI module, Exhaust manifold, Fuel system, Tranny mods, etc) but now that the magnum he bought is not worth installing without rebuilding, it causes me to second guess the whole approach. My son has learned a lot already just in rearing down the magnum, cleaning it, and taking all the measurements to determine how worn it is. So yes, good father-son project.

 

Welcome.

I don't see this as a Carb/EFI choice but a Flat Tappet/Roller Lifter choice, me I'm going Magnum all the way. Hold on to the EFI/Computer system but put a Carb on the Magnum.

Roller gives you any oil choice with no break in problems that many are having these days.

 

I would rebuild the magnum. It’s a roller cam motor and the blocks are actually really good. The head may have cracks in them between the valves it’s pretty common but if it will pass a leak down test I would run them. You can purchase iron heads that are drilled for la manifolds at a reasonable price from hughes. Also if you get an hei kit you don’t need the computer and can run it carbed. I’m doing it right now with a 360 magnum. If you get heads I would do the head stud kit and do roller rockers you can get studs that will accept Chevy rockers and run those just fine. A stock cam is around 150 on eBay. And if the lifters are good you can reuse them. If you just swap the motors out right you can use the la318 dizzy and it droppes right in and run all the electronics. You will just have to add the voltage Reg to the alternator circuit because the magnums is regulated by the ecu and an electric fuel pump. I hope this helps. The blocks are almost identical.

 

Thanks for weighing in cmdedge.
Since my original post we found a 92 Magnum with 80k miles and took that engine and started over. We changed a few obvious components and installed it in the truck. Pain in the butt to mate it to the 86 manual tranny due to some bell housing clearances. Had to use LA exhaust manifolds because the Magnum ones exited on top of the starter and clutch pedal. We may replace those with headers in the future but my son didn't have the additional funds to buy them now. We used Magnum as it came; stock intake and computer. Of course we had to make several modifications to adapt the 86 chassis to the new engine. Things I recall were 1) Install the High pressure fuel pump in the old tank. We had the pump and wiring harness from the 92 and had to modify the old tank to use it. We cut the plastic housing from the donor tank fuel pump assembly and sealed and riveted that into the original tank on the 86. We used the fuse box from the Magnum donor because it had a fuel pump relay and other fuse circuits we found useful. You could certainly pick other options here such as an inline fuel pump and separate fuel pump relay. 2) There were a hand full of wiring mods such as Neutral/safety switch, Temp sensor, oil pressure sensor, etc. 3) We used the complete wiring harness with fuse box and computer (ECM) from the Magnum donor. The engine cranks and runs although a little rough at the moment. At this time, we have no exhaust on it at all; he is saving his money to get that done. We will work on getting it running better once it has an exhaust system. To your comments on other EFI solutions, we REALLY wanted to go that route (Holly or other) but we would have had to get another intake manifold and then the EFI solution. The Intakes are expensive for the Magnum. Together it was $1,500 at a minimum and he didn't have that money to spend. So we used what he had and could get working. So, in the end he seems content with the project and he's learned a ton. He just has to save his money to get the exhaust installed and work out the fine tuning issues. I hope the engine holds up for him for a while... he and I are both tired of working on it - at least for a while
Thanks for the help to all those on this Forum!!