View Full Version : Magnum 318 vs. 360 flywheel balancing

11-10-2000, 06:11 PM
I'm still considering swapping a 360 into my 318 powered Ram so I'll need the external-balanced flywheel and harmonic balancer from a magnum 360. The balancer is reasonable at $176 Cdn but the flywheel is $760.

Is there a kit/procedure to either weld balancing weights or drill my 318 flywheel? I think there is a kit to modify the flexplate on an automatic, so hopefully one exists for the flywheel as well.

1994 Ram 2500 4x4 RC
318, 14" k&n, 3" exhaust, MP PCM, 180 stat
NV4500 5spd, 4.56 gears, detroit rear, 255/85/16 MT's

11-10-2000, 11:38 PM
Does the 360 have a balancer on it? If so, just leave it on. I might have a used flywheel for a 360 that would have to be cut. If your interested. Just e mail me.

11-11-2000, 12:21 AM
No balancer comes with the 360 longblock but I'll buy a new one for $176. Is your flywheel for a magnum 360? The magnum 360 flywheel is different than the LA 360.


11-11-2000, 02:51 AM
Yes it is for a Magnum 360. It has some hot spots in it, thats why it needs cut.

11-11-2000, 11:39 AM
If memory serves me right, the rear external balance on a Magnum 5.9V8 is 14 oz-inches.

That means you would need to weld on a weight of 14 oz at a distance one inch from the center of the flywheel at the specified angle from top dead center, or 7 oz at a distance two inches from the center, or 3.5 oz at a distance of 4 inches, etc.

The 14 oz-inches is less balance correction than the old pre-Magnum 360V8 had because the pistons of the Magnum are lighter.

The 'Magnum' style of flywheel has a series of eight slots cut into its outer edge that the Crankshaft Position Sensor reads to fire the ignition timing correctly.

The Book:
Chrysler Performance Upgrades
by Frank Adkins
published by CarTech as part number SA-60 in 1999.
ISBN 1-884-089-40-2

has a good picture of the Magnum flywheel, and I think a pictures of the weights to be welded on.

11-19-2000, 01:11 PM
I see from the posts below that I may need to change the flywheel and balancer. No problem there but, what about the computer? Also, will the transmission from the 318 handle the torque from the 360?
I have a 96 Ram extended cab with a 318 and auto transmission. I was going to modify my 318 but, after 3 months, the shop is no closer to finishing than the day I dropped it off. So, this week I'm going to take it somewhere else and either have a remanufactured 318 or 360 dropped in. I'd rather go with the 360 if at all possible.
I'd appreciate any help you can offer.

11-19-2000, 02:42 PM
There are three possible ways you could get the fuel injection to work:

1. Get a junkyard PCM computer off a 5.9/360 V8 of the right year. Cost about $150-300.

2. Get a set of 24 lb/hr fuel injectors like the Ford Motorsports ones advertised in the Summit catalog. Cost about $250.

3. Play around with the fuel pressure so that the individual fuel injectors squirt more than the 318 PCM computer expects. To do this you would have to dis-assemble your pressure regulator inside the gasoline tank and either replace the spring with one heavier, or stack shims in line with the spring. You would need to get the fuel line psi to rise to about (42 psi) times SQUARE (360/318) = 54 psi. This would take experimenting. Cost: much of your labor + $20-$50.

The best option is number 1.

11-20-2000, 01:03 PM
Here's a post on another board you should read. It might be good news. You might be able to use your 318 computer with your 360 shortblock without many problems: