John
Guest
Find a "Series 3" Shop Manual and spend some time thumbing through it. It has most of the updates in it or how to do the update to get the earlier N's to the Series 3. The one thing that really sticks out is the engine, one is the 670HI and the other is the 670I. The main difference in them is that the HI runs at 200-300 RPM faster with a counter balanced crank to get the same 220 HP for the N6. Most of the 670HI blew up due to the RPM's, they also blew alot of fuel out the exhaust pipe(Coal locomotive on a long uphill grade). The later N6's were beefed up as was the N7's for the extra weight and load. Even my Series 3 N6 with tank extensions to the N7 capacity was breaking axle bolts between the axle and the final drive housing.