1978 Cherokee 4.0 build up

[Carl Rasmussen]

I bought this a few months ago but just really got started on it. I it a 78 Cherokee Chief
Here is hopefully what it will have when done
I posted this in the off-road tech because this is an off-road build up so the entire project will be in the same thread

Engine: 2002 4.0 L6
Trans TH400
Transfer case NP 205
Axles D60, 14bolt
Gears 4.56 Detroit
Tires 38-> 42 range
SOA and Shackle Flip

I started today working on installing the engine.



I found out that I can not use the stock flex plate, because the torque converter had 3 bolts and the flex plate was drilled for 4 bolts. I determined that I could just use the stock flex plate from the 360 since it had the same bolt pattern on the crank as the 4.0. I will have to use the starter from the 360, because the ring gear on the flex plate is offset in a differ place and the 4.0 starter gear will not reach out far enough.

I was going to use the stock 258 engine mounts on the engine to make things simpler but when I try to bolt the mounts to the block I found out that the 4.0 block was machined different than the older 258. So I decided to make my own using the TJ Mounts already on the engine.

I bolt the engine up to the tranny to see how everything was going to fit and so I could start making the engine mounts.



After measuring a few things I determined that the engine needs to move back about 4", where it sits now the fan will be though the radiator.

You can see the radiator support mount hole in the frame is right where the radiator is.



I checked to see if I had enough room to move the engine back far enough. I don't think that will be too much of a problem. I have plenty of room between the back of the engine and the fire wall. I think I will still clear the brake booster but it will be close.




Everything else fits in there pretty well. Here are the rest of the pics. I will post my progress each step of the way




[ September 11, 2005, 07:43 PM: Message edited by: Carl Rasmussen ]

[Carl Rasmussen]

[Crazy_Jeepman]

I would not use the 360 Flexplate either as it is not ballanced for the I6. I would get one from a 258 79 and down would be my guess.

[Carl Rasmussen]

ok I will do that thanks

[Crazy_Jeepman]

Originally posted by Carl Rasmussen:
ok I will do that thanks

I would double check with someone that is a bit more versed with the balancing of the motor you have. I am only assuming that it is balanced the same as the 258. I am really not that familiar with all the I6's. I would guess it to be the same, since it is based off the 258, but make sure. Should be a nice swap when you get it wrapped up

[Carl Rasmussen]

ok I checked online and there are 2 different part numbers for the 360 and the 258 fly wheels.

So I think the 258 would be the best choice.

[ September 11, 2005, 08:17 PM: Message edited by: Carl Rasmussen ]

[JeepsAndGuns]

I would think somewhere like advance adapters should know. Call and ask them. Tell them you are bolting a 4.0 to a th-400, they should be able to help you with finding a flex plate.

[Stuka]

The 258 in an i6 has about 3/4" clearance from the firewall to the back of the head. If you have several inches, it wont clear the radiator.

Looking good thus far [img]smile.gif[/img]

[Carl Rasmussen]

did the 258 ever come with a TH400. I ask this because my tranny cross member is allready all the way back. I will have to drill new holes

[joe]

Good going Carl! You'll like the 4.0. It's not the tractor motor the 258 is but for drive-ability and longevity it's a sweetheart.

[Stuka]

Yes the 258 came with a TH400 and a QT (no low range though, doesnt clear the fuel tank). But I am not sure what the setup was for the trans mount. I am guessing the rear frame holes for the XM, and the rear holes in the XM for the trans mount.

[Carl Rasmussen]

You know it is funny how some people on other boards (PBB) think I am nuts to go from a 360 to a 4.0 they say it will be a DOG. I know it will not be a Rocket but the ones I have had in my baby jeeps really get it when you get on the gas.

I may not pass them on the freeway but I will at the gas pump

[ September 11, 2005, 08:39 PM: Message edited by: Carl Rasmussen ]

[Carl Rasmussen]

Originally posted by Stuka:
Yes the 258 came with a TH400 and a QT (no low range though, doesnt clear the fuel tank). But I am not sure what the setup was for the trans mount. I am guessing the rear frame holes for the XM, and the rear holes in the XM for the trans mount.

That is what I thought but it is allready in that location an I nee to go 4" futher back.

Before I move it will have to get the NP205 connected and see it thing are still in the same place.

[Stuka]

I will take a photo of my 258 tomorrow with a tape to show the distance from the firewall and radiator.

[Knucklehead]

I would be sure that the 258 flexplate will balance the 4.0. I doubt that they will because the stroke is different by almost 1/2" and the piston weights are different as the 258 has a smaller bore than the 4.0. If you don't use the correct flywheel you will ruin your motor in short order.

Otherwise I like what you are doing and am actually doing the same in a month. The motor is at the machine shop at the moment. This info will help me out a lot. Thanks.