Project Magnum YJ

bmgadg · 04-12-2010, 11:51 AM

I've decided that my yearly project this year should be a v8 swap. I did the 4.0 swap last spring because it was simple and fairly inexpensive as far as motor swaps go.

I wheel with guys in big full size trucks all the time, no rocks in MS just trail riding and mud

Don't get me wrong, the 4.0 is a huge improvement over the 2.5 turd that was in it when I bought it, but it just isn't enough for me. So, after studying the 318 5.2 magnum v8 swap, I decided that's the way to go and picked up a v8 at the local pull a part this past weekend from a Dodge v8 work van.

Here's the game plan for this build....

1. Get a 318 5.2 v8 engine for rebuild
2. Get ODB1 computer and wiring harness
3. Get a bellhousing from a v6 Dakota to adapt the AX-15 I already have to the small v8 and retain the NP231 t-case
4. Use 4.0 Jeep clutch set and pilot bearing
5. Finish building up full width D44 front and 8.8 rear with 4.10 gears
6. Waggy springs SOA

So after completing steps 1 and 2, I started cleaning up the engine this weekend and I notice this casting number on the side of the block...

The casting number shows that this engine is a 360 5.9, not the 318 5.2 that I thought it was! This is a huge monkey wrench in this project. I was expecting to keep the AX-15 with the 5.2 because I've read that it will handle mild v8 power, but check these specs out on the 5.9...

250 hp (190 kW) and 345 lb·ft

So my question is will the AX-15 hold up to that kinda power or not? My suspicion is it will not. I'm pretty sure it will still bolt up to it with the Dakota bellhousing.

Anyway, I'm going to be logging my findings and progress here over the next few months. My YJ isn't a daily driver, so I can take my time with it. I estimate it will take most of this spring and summer to finish because I only have weekends to work on it.

Wish me luck!!

93jeepyj · 04-12-2010, 12:36 PM

Well the stock 4.0 puts out 185 hp I think so 250 isnt a huge jump but the torque increase might be the killer. Ive kinda had the same idea in the back of my head for a year or two now. I replaced my 4.0 with a 05 4.0 with like 15k on it from a rolled tj and while it runs great ive been kicking myself for not going v8 then ever since.

bmgadg · 04-12-2010, 12:37 PM

Other issue to be worked out is fuel delivery, I don't see any regulator or return line on the manifold, so does that mean it's regulated at the pump in the tank? I really need to get a FSM for this motor!

bmgadg · 04-12-2010, 12:40 PM

Quote:

Originally Posted by 93jeepyj

Well the stock 4.0 puts out 185 hp I think so 250 isnt a huge jump but the torque increase might be the killer.

Torque is my big concern too, 110 lbft of additional torque is a big deal I think.

wickedoffroad · 04-12-2010, 04:20 PM

I put a 318 V8 out of a 1978 dodge 3/4 ton pickup in mine. I kept the original np 435 4 speed and traded out the np 203 for a np 205 ( pumpkin on wrong side) So far I haven't noticed any problem with the stock d35 axle handling 33x12.5 tires, I am sure its only a matter of time tho.

NOVA87Wrangler · 04-12-2010, 07:09 PM

I've got a 5.3L V8 mated to an AX-15 with no issues yet. Specs are 305hp/350ft-lbs. Mine is also a return-less system but I'm using an aftermarket regulator in the engine compartment with an inline electric fuel pump from an 80 Ford F250 I think? That truck has an intank pump and a pump on the rail so I bought the rail one. Puts out the 60psi needed for my fuel rail no problems.

bmgadg · 04-12-2010, 09:10 PM

Quote:

Originally Posted by NOVA87Wrangler

I've got a 5.3L V8 mated to an AX-15 with no issues yet. Specs are 305hp/350ft-lbs. Mine is also a return-less system but I'm using an aftermarket regulator in the engine compartment with an inline electric fuel pump from an 80 Ford F250 I think? That truck has an intank pump and a pump on the rail so I bought the rail one. Puts out the 60psi needed for my fuel rail no problems.

Sweet, that makes me feel a lot better. I'm going to have to put some thought into fuel delivery, and your setup gets me thinking...

ritjobbie · 04-12-2010, 09:26 PM

Did someone say Magnum?

warthog312 · 04-13-2010, 02:13 PM

i blew up 3 transmissions in my old Dakota R/T with the 360. granted i was going high 12's with it, but even stock i wouldnt recommend the stock jeep trans. its all about the torque, and less the trans i would worry about u joints, xfer case, shafts, just about everyhting. those motor even in stock form can blow stuff up from torque. just my .02

Roadyy · 04-13-2010, 02:34 PM

What part of mississippi are you in ? I moved down to Fl. from Columbus,Ms. If close to there I go up every month or so would be willing to add couple hands when I do if needed.

bmgadg · 04-13-2010, 02:37 PM

Quote:

Originally Posted by UABYJ94

What part of mississippi are you in ? I moved down to Fl. from Columbus,Ms. If close to there I go up every month or so would be willing to add couple hands when I do if needed.

Vicksburg, about 3.5 hours from Columbus. Thanks for the offer though!

MoparFreak69 · 07-26-2010, 06:34 PM

Just a few thoughts on fuel delivery and transmissions.

You are probably better off getting a fuel rail off of a Grand Cherokee that has a built in fuel pressure regulator. It makes things a bit easier because it is already set up to regulate the pressures the system needs. I got an external fuel pump from Summit racing for like $140 and just extended my pickup tube to the bottom of the tank with a strainer sock on the end to keep the chunks from going into the main filter. I powered mine off the existing fuel pump wiring and its working great.

Beware that the 5.9 is EXTERNALLY balanced, unlike the 5.2 which is INTERNALLY balanced. You cannot use a flywheel off of a 5.2 on a 5.9. Your best bet is to get a 5.9 flywheel and have the pressure plate holes drilled for you at a local machine shop. The route I went was to get a 6 cylinder flywheel from one truck and put an 8 cylinder tone ring on it. Hindsight says I should have just gotten the 5.2 flywheel and had it drilled and been done with it. If you choose to go automatic you need to make sure you get a torque converter for the 5.9 for the same reasons. It has weights welded to it to assist balancing the engind correctly.
Install the wrong flywheel/torque converter and that engine will beat itself to death in short order.
Will the AX-15 handle the 5.9? Sure, if you can drive like there is an egg between your foot and the accelerator pedal. After I got the clutch hydraulics working right on my swap I am loving the gear ratios of the AX-15 behind the 318. Coupled with my stock 4.10's in the stock axles and I have the real potential to produce some carnage, but after wheeling quite a bit I am confident that as long as I control wheel spin I will be just fine.

bmgadg · 07-27-2010, 08:29 AM

Quote:

Originally Posted by MoparFreak69

Just a few thoughts on fuel delivery and transmissions.

You are probably better off getting a fuel rail off of a Grand Cherokee that has a built in fuel pressure regulator. It makes things a bit easier because it is already set up to regulate the pressures the system needs. I got an external fuel pump from Summit racing for like $140 and just extended my pickup tube to the bottom of the tank with a strainer sock on the end to keep the chunks from going into the main filter. I powered mine off the existing fuel pump wiring and its working great.

Beware that the 5.9 is EXTERNALLY balanced, unlike the 5.2 which is INTERNALLY balanced. You cannot use a flywheel off of a 5.2 on a 5.9. Your best bet is to get a 5.9 flywheel and have the pressure plate holes drilled for you at a local machine shop. The route I went was to get a 6 cylinder flywheel from one truck and put an 8 cylinder tone ring on it. Hindsight says I should have just gotten the 5.2 flywheel and had it drilled and been done with it. If you choose to go automatic you need to make sure you get a torque converter for the 5.9 for the same reasons. It has weights welded to it to assist balancing the engind correctly.
Install the wrong flywheel/torque converter and that engine will beat itself to death in short order.
Will the AX-15 handle the 5.9? Sure, if you can drive like there is an egg between your foot and the accelerator pedal. After I got the clutch hydraulics working right on my swap I am loving the gear ratios of the AX-15 behind the 318. Coupled with my stock 4.10's in the stock axles and I have the real potential to produce some carnage, but after wheeling quite a bit I am confident that as long as I control wheel spin I will be just fine.

Thanks for the info! Will the GC fuel rail have a return line off the regulator? I was looking into getting an external regulator from summit with a return line but if the GC already has it I can pick one up at a junk yard way cheaper. I think the stock fuel pump for the 4.0 will provide enough psi, but will it provide enough volume?

You're scaring me now about the ax-15! I got a dakota bellhousing from the junk yard last week, fits great but now I'm wondering if I need to upgrade to a nv3500 or nv4500??

bmgadg · 07-27-2010, 08:37 AM

New progress....

Got the SYE installed on my np231 this weekend. Wasn't too bad except I had to shorten the rod about and inch, in the instructions it said that was common for 88-89 models

MoparFreak69 · 07-27-2010, 04:18 PM

Here is the rear of the Grand Cherokee fuel rail I installed during my swap. The blueish circle is the inlet and the red circle is the outlet. The outlet hose connected right to my QD on the Jeeps return hard line. The supply line was larger so I had to connect the old supply hose to the new supply hose with a double barbed fitting.

As far as fuel pump, its really dependent on setup. I was running an in-tank TJ 4.0 fuel pump and was having issues, but that was partly because it was mounted up strangely and would lost prime if I cornered too hard. I just went with the external because it was rated what I needed and was the same cost as an in tank. I say go with what you got and if you have driveability issues then go from there.