Big Cam 1 400 CPL 393

The only big difference between the 1 and 2 was the lower oil psi. Lower psi pump. The 3 had oil cooler and oil flow changes like the bypass filter added to cooler to no longer need the luberfiner 750.

 

Bearings ate the same. The main reason for the change to lower psi was bearing washout (errosion). They came to the conclusion the lower psi put less wear on the bearings and made them last longer miles. I know many small cams and bc1’s had the lower psi pumps put on them during an overhaul. The NHC 250 in my White with original pump will cold start at close to 100 psi in winter and 80 in summer months. They were thinking thats pretty harsh way to wake up them bearings I guess.

 

They didn’t change the design of the bearings but the numbers always coincided with the crank and rods cpl or cut. Go with the same bearings that are on the crank now if it doesn’t need to be cut. The oil pump had nothing to do with what bearings were used.

 

Its the pump itself. The oil pump is like a fire hose pump. It can pump a lot of oil fast. The low psi pump is same size, looks same, bolts up the same, it is just the internal psi regulators inside that changed the psi. I’m not sure about the newer replacements but the first earlier ones were made tamper proof so you couldn’t get into them and screw with the regulator. Some old timers were taking the older hi psi pumps and playing with the psi thru changing springs in them.