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Here are some notes and things that I learned while doing a 318 to 360 swap. Hopefully, these can help a first-time swapper to avoid some trouble and make the swap a bit easier.

The 360 was pulled from a 1979 Cordoba and was installed in a 1973 D-100 pick-up with the original 318. The '73 has a 727 transmission, no power steering, A/C or smog equipment.

To keep this fairly short, I am skipping over any maintenance parts replacement (plugs, wires, water pump, hoses, etc). It is assumed that you have a complete & functional 360 to be installed or a freshly rebuilt motor.

Also note that there may be some casting differences in the blocks, depending upon the year of the block. My 318 had four motor mount ears cast into each side of the block. Owners of later 318s have told me that there are only 3 ears on their blocks. The 360 had 3 ears.

Unfortunately, I could not locate a 360 donor truck for parts. This created several challenges…

First, since the 360 came out of a car, it had a center sump oil pan. Trucks require a rear sump pan. Even if the 318 had come out of a truck, the 318 and 360 oil pans are different and not interchangeable. I bought a new rear sump 360 oil pan, and oil pick-up. It was a complete Mopar Performance oil pan kit (PN: P3690715 pan, pickup, gaskets) from PAW for $80.

Then there were other issues to deal with…

Torque converter or flexplate:

The 318 is internally balanced. There are no weights on the torque converter.
The 360 is externally balanced. There is a large weight welded to the torque converter.

The torque converters are not interchangeable outright. You have two choices here:

Install a 360 converter and be done with it. Probably the easiest thing to do, especially if you pulled the converter with the donor engine. I had the Cordoba converter, but it was a lock-up type converter, which requires a lock-up type 727. My '73 did not have a lock-up 727. So, using the Cordoba converter was not an option.

Use the existing 318 converter with a weighted flexplate. Since the 318 converter has no weights, there has to be some way to balance the 360. This can be done by using a special flexplate from B&M. The part number is 10236 for a 727 trans and 10239 for a 904 trans. I found this for $75 from PAW. The B&M piece just bolts on in place of the OEM flexplate and allows you to use the 318 converter. I went this route because I had rebuilt the trans and installed a new converter a few months before. I couldn't see buying a new converter, although it would likely have been cheaper than the flexplate. However, there is another advantage to using the B&M flexplate. Most aftermarket torque converters (racing, high stall type) are neutral balanced…not weighted. If you decide later to upgrade the converter to a high stall, you only need to drop it in. If you keep the 360 converter and stock flexplate, you may have a more limited selection of aftermarket choices.

Motor mounts:

(This information refers to truck applications. Car applications may be different)

Here again, the easiest thing is to acquire a set of 360 truck mounts to use in your install. Since the car mounts are totally different, I could not use the ones I retained from the Cordoba. But the bolts would be handy later.

The U-shaped metal part of the mount for the 318 and 360 is essentially the same. The rubber isolation "sandwich" part of the mount is the same for both motors. In my application, I reused the metal part of the mount when installing the 360 but swapped the 318 mounts to the opposite sides. Left side mount went on right side of block and vice-versa. This is because of the casting ear differences in the blocks. With the mounts swapped, I found that the mounts would fit almost perfectly if the mount tabs were towards the front of the casting ears on both sides of the motor.

The left side mount was a perfect fit to the motor and the rubber isolation pad. The right side mount fit the casting ears nearly perfectly, but required using a washer as a spacer on the rear ear. Also, the slot in the mount did not line up with bolt on the isolation pad. I drilled a hole slightly forward of the slot. This made a perfect fit for the mount.

Luckily, I saved the bolts from the Cordoba mounts. As it turns out, the casting ears on the 360 are also thicker than the 318. The original 318 bolts would fit all the way through the mount, but the nut would not screw on fully. The 360 bolts were plenty long and were used to secure the mounts to the block.

Miscellaneous:

One other thing that needed to be done during this swap involved the exhaust ports. Specifically, the air injection holes. The '79 motor had small holes directly below each exhaust port. These holes are there to allow fresh air from the smog pump to be injected into the exhaust ports for emissions. These holes are were cast into several years of heads, but are only actually used in a few applications.

Since the '73 is pre-smog pump, and my exhaust manifolds had no provision to seal the holes, I needed to plug them to prevent any exhaust leaks. I did this by threading the holes with a ¼" x 20 tap. This tap size will allow you to tap threads without additional drilling. Then I simply used ¼" x20 set-screws in 1/8" length (available at most local hardware stores), with some sealer applied to the threads, to plug the holes.

I found that it was actually easier to tap the threads with a dry tap. (This is not the typical practice.) Tap the holes very slowly. Breaking off a tap in the head would be a very bad thing.

Harmonic balancers:

The balancer on the 318 was 15/16" thick. The 360 balancer was 1 3/16" thick. I was reusing the alternator and all pulleys and brackets from the 318. I had to shim the fan pulley and alternator pulley out to line up with the crankshaft pulley. Oddly enough, I only shimmed less than 1/8". It seems that although the balancers are ¼" thicker at the edge, the thickness of the metal were the pulley mounts is much closer.

Overall, the swap was fairly simple and went smoothly. Aside from the above items, the two motors are virtually identical and all other accessories will swap directly.

Good luck with your Mopar upgrade!

This FAQ was originally written by AZ_Drummer
 
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