I'm doing a 318 conversion, and here's some info


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Posted by Brian in Oregon on Monday, October 23, 2000 at 02:03:55:

In Reply to: 318 info posted by Peter Hewko on Monday, October 23, 2000 at 00:23:22:

Just went through this myself for finding a 318 motor.

Basically, you want a 318 built from 1971 on up. The water outlet was changed in that year and it points to the passenger side. 1970 and earlier point to the drivers side. You'd have to change the lower tank outlet on the radiator to match, which is expensive. You also want a non-air conditioned engine so you don't have to play around with pulleys. Power steering is optional, as Helitool and Snake River have kits.

(In my case, I went with a 318 out of a 1972 Dart that had air conditioning. Turns out the motor was made in 1968, and it has a desireable forged crank. The front timing cover and water pup were changed to the later style, but no I'm having fun finding a pully combo that fits. This is the penalty for getting the desirable forged crank, I guess.)

You will also need a rear sump oil pan from a truck (assumming you bought a passenger car motor), the appropriate truck dipstick, and one extra center dump exhaust manifold (most passenger cars have a center dump on the passenger side and a rear dump on the drivers side.)

If you are running a short tailshaft 727 Automatic, you just need a flexplate and converter to match.

If you are running a stick, you can run an NP435 if you don't need the PTO winch, or you will likely need to run the original NP420 if you do want the PTO winch. (Yes, there are NP435's with a drivers side PTO, but they are the proverbial hen's teeth.)

To do the 318?NP420 conversion, in addition to Ray's kit, you'll need a CAST IRON bellhousing from a 318/NP435 truck. You will need the one with a mechnical clutch, which has no mounting ears. (The hydraulic version has mounting ears to mate to the frame.) Ray's kit has the mounts. DO NOT use the aluminum bellhousing, even though it is identical to the cast iron one. Nice idea to save weight, but will it support the full weight of the NP420 if you take a heavy landing shock with your M37? Ray and I have our doubts it will.

Ray's site better explains the install and has photos as well. Check out the WDX conversion for a 360/NP435.

As far as hot rodding the 318, I see no reason for it. It might be an idea to put on an aluminum 4-barrel intake so you can cruise on smaller primaries, thus getting higher flow velocity which should help mixture a bit and mileage a wee bit.

If you run stock gears and tires, you'll probably be turning somewhere around 3500 rpms at 55 mph. This is doable for all but very tired motors. If you rebuild your 318, balancing will help in this respect. Pushing it to 60 or 65 mph is probably not a good idea without a gear change, and in my opinion a motor running at 4000 rpm sustained needs to be balanced.

One more thing - brakes. They simply are not up to stopping an M37 from 55 mph. Check out Ray's disc brake conversion while you are at it.



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