TheEddie Posted February 1, 2014 Report Share Posted February 1, 2014 Curiosity kills the noob...well, that plus inability (laziness?) to use the "search" button... :blush: I have different year factory 620/720 service manuals, the earlier ones showing an L-series engine with a conventional separated (1) water pump with flange and studs, (2) drive pulley, (3) fan clutch. The later manuals show various iterations of the NAPS-Z motor, which apparently uses an integrated, non-separable water pump/drive pulley/fan clutch. What gives? Why did Nissan go to the later style? My SWAG is that the one-piece assembly is slightly shorter than the earlier built-up assembly, and that Z-motors used a thicker cam-drive chain case which pushed the earlier assembly into the fan. Eddie Quote Link to comment
datzenmike Posted February 1, 2014 Report Share Posted February 1, 2014 I only have seen the integral clutch fan and water pumps. All my L20Bs have them and all the S110 (200sx) and 720 Z20E, Z22S and Z24 motors I have seen were this way. I understand there were some that were separate clutch bolted to the pump but haven't seen one. I have seen one 720 Z22 with pump and no clutch but figured someone cheaped out and fitted an earlier L16 pump to it. The L20B clutches were smaller diameter with different plastic fan blade diameters to reflect this. The Z series pump cavities are also larger with a larger impeller to move more water. L series water pump. Note the cast smooth impeller and the pump cavity just below it... Later Z series pump cavity is much deeper with a larger smooth cast impeller... This is a cheap stamped impeller pump that will cause cavitation with all the sharp edges. These are crap and should be avoided. L20B and Z series clutch fans and blades. Note the Z series is larger. Pumps are interchangeable but fans are not. You must swap blades with the pumps. What gives? Why did Nissan go to the later style? My SWAG is that the one-piece assembly is slightly shorter than the earlier built-up assembly, and that Z-motors used a thicker cam-drive chain case which pushed the earlier assembly into the fan. Eddie Overall the integral pump and clutch fans will be shorter than ones bolted together but not because of timing case thickness. The L20B and Z series (Z20 and Z22) timing covers are identical except for the gasket area where it joins the head. Quote Link to comment
TheEddie Posted February 3, 2014 Author Report Share Posted February 3, 2014 'Preciate the info! I never thot about the possible hydrodynamic qualities of a cast impeller v. a stamped piece...but a cursory glance over the different pics (above) sure showed it: notice the convex/concave and tail shapes of the fins, cast v. stamped. Far more efficient, OEM v. later. I went to O'reilly AP's site, and they had two pumps available: A reman, and a new. Sure enuff, the reman had a cast impeller, the new had the stamped. THANX! One-piece pump/pulley/clutch unit: "Why?"...Well. I guess that has to be one of life's big mysteries. Perhaps they will solve it in the far future. I'll spend many a night, lying wide awake in the wee hours, staring into the dark, wondering...wondering... Eddie Quote Link to comment
datzenmike Posted February 3, 2014 Report Share Posted February 3, 2014 Compactness is my guess. I sleep just fine. Quote Link to comment
harlow426@msn.com Posted February 3, 2014 Report Share Posted February 3, 2014 My "departed" 82 720 never had a clutch(Z22)...4 vane fan. SOOO much quieter as well!!!! I really dislike the wind noise created by the fans they put on the clutch units. Robbed the one off my Z22 for my l20b b-cause the noise was diving me crazy(er). All that extra mass on the pump harder on wp bearing as well. In the Pacific NW where I live 93.5% of the time u don't need a fan.....pulling big trailer, 90 deg heat, makin it "work". If u sit and idle tooo long it will build heat......1/2 mile later cools right back down. On topic but not....veggie oil in the coolant helps quiet a noisy wp bearing & gives u a few more miles b-4 pay-day.{half cup 2 a gal water}. Flushes out easy with powdered dish soap(1/8 cup). It is amazing how much crap gets flushed out if u use powdered dish soap....better than any auto parts store product. B-sure to rinse/flush till h2o comes out clean then add coolant otherwise the "insides" will start rusting. Quote Link to comment
ggzilla Posted February 3, 2014 Report Share Posted February 3, 2014 That's the point of a clutch fan. To stop spinning when not needed. A regular fan is on all the time the engine is running. But since they are smaller, less noisy. Quote Link to comment
datzenmike Posted February 3, 2014 Report Share Posted February 3, 2014 Yup. If a clutch fan sounds like an F-18 taking off it's because it's seized. They are limited to 1,500 RPMs or less and save energy. Quote Link to comment
tubbedbaggedstockfloored65 Posted March 10, 2014 Report Share Posted March 10, 2014 ratsun family got a question i have a 1975 datsun 620 with l20b and i have the big fan blade on the bottom right of this picture and i was wondering what water pump to buy that that clutch fan will bolt onto on rock auto the difference between the two water pumps are clutch fan size and fan size the one with bigger fan clutch and fan says with a/c on rock auto and the small one doesnt, i dont have ac on my truck but cant i order that bigger water pump with the bigger clutch fan and blade and my fan should mount up or are there different sizes other than those 2? i am confused any help would be appreciated Quote Link to comment
ggzilla Posted March 10, 2014 Report Share Posted March 10, 2014 Yes, if you have the 5.25" fan, buy the matching water pump. You can replace it with the original non-AC 4" pump but then you'll have to find the smaller fan. Your choice. Quote Link to comment
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