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| techtalk:ih:oil03j [2025/09/06 16:11] – [What Era Factory Oil Pump Would Be the Most Benificial on a Street Performance Build] hippysmack | techtalk:ih:oil03j [2025/09/06 18:04] (current) – [Installing 1972-1976 Oil Pump (Complete) on 1971-Earlier Motors] hippysmack | ||
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| The 1975-1987 XR-750 pump does not have a feed bypass. But it does have a hose nipple in the rear of the pump just like the -72 production pump does. And that nipple is tied into the return gears instead of the feed gears. This pump has no external inlet for tank feed oil as required to mount on 1967-up XLH and 1970-up XLCH. \\ | The 1975-1987 XR-750 pump does not have a feed bypass. But it does have a hose nipple in the rear of the pump just like the -72 production pump does. And that nipple is tied into the return gears instead of the feed gears. This pump has no external inlet for tank feed oil as required to mount on 1967-up XLH and 1970-up XLCH. \\ | ||
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| + | 1954-1976 KH and Sportster pumps do not have afeed bypass built in although there were a few different versions of those as well. \\ | ||
| ====== What Era Factory Oil Pump Would Be the Most Beneficial on a Street Performance Build ====== | ====== What Era Factory Oil Pump Would Be the Most Beneficial on a Street Performance Build ====== | ||
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| ====== Installing 1972-1976 Oil Pump (Complete) on 1971-Earlier Motors ====== | ====== Installing 1972-1976 Oil Pump (Complete) on 1971-Earlier Motors ====== | ||
| - | * The bigger return gears in the -72 pump suck up more oil at a higher suction (vacuum) rate. | + | * The bigger return gears in the -72 pump suck up more oil at a higher suction (vacuum) rate. The faster they rotate, the more vacuum is created. |
| * As mentioned above, the return hole in the case mounting surface needs to be enlarged with a second hole to lower the added vacuum generated by the return gears. Gravity does little to flow oil through that return hole. The pump depends on suction (vacuum) from the gears AND positive crankcase pressure (piston downstroke) that makes it's way into the cam chest to push the oil in the cam chest sump (below the cam floor screen) to the oil pump's vacuum chamber. | * As mentioned above, the return hole in the case mounting surface needs to be enlarged with a second hole to lower the added vacuum generated by the return gears. Gravity does little to flow oil through that return hole. The pump depends on suction (vacuum) from the gears AND positive crankcase pressure (piston downstroke) that makes it's way into the cam chest to push the oil in the cam chest sump (below the cam floor screen) to the oil pump's vacuum chamber. | ||
| * Lowering the vacuum created from the bigger gears in the -72 pump also allows the pump to suck up more oil without added stress, which lowers the possibility of making froth in the oil due to higher vacuum sucking on the single inlet hole in 71< motors. | * Lowering the vacuum created from the bigger gears in the -72 pump also allows the pump to suck up more oil without added stress, which lowers the possibility of making froth in the oil due to higher vacuum sucking on the single inlet hole in 71< motors. | ||
