Willhoit Anti Drain Back Valve, 911 (65-89)
Regular price
$448.58
| Brand: | Willhoit |
| Model: | 911 |
| Years: | 1965-1989 |
| WH Rack: |  G13-6 |
Willhoit anti drain back valve for 911 (1965-1989) models.
Four-cam cars, and all 911's up to 1989, have a dry sump oiling system. The oil for the engine is stored in a tank in the fender well and not in the crankcase as in a wet sump engine (like the 356).
A dry sump system has several advantages:
- Since no oil is stored in the crankcase, the engine case can be made smaller and the engine can be mounted lower in the car, lowering the center of gravity.
- Oil can be immediately evacuated from the crankcase with a scavenge pump, reducing oil drag on the crankshaft.
- A larger amount of oil can be carried in the tank, and controlled with internal baffling so that oil is constantly available even during hard cornering.
The disadvantage of a dry sump system is that it is much more complex. It requires a separate oil tank and the necessary lines. It also requires a two-stage oil pump for pressure and scavenges. Almost always the oil tank is mounted above or at the same level as the engine. This is the case with the four-cam and 911 models.
When the car is parked, especially for long periods of time, oil will migrate through the oil pick up hose, through the oil pump, and into the crankcase. When the oil level gets high enough the oil can then enter the lower valve covers, migrate down the exhaust guides and into the exhaust port. This is especially bad on the 4 cam engines with their large 11mm exhaust guides, and low exhaust valve covers. It’s not unusual for all pre-1989 911s and 4 cam cars to produce a cloud of smoke on start-up, especially after being parked for more than a few days. The newer, thinner, oils have made this even worse.
The WR Anti Drain Back Valve is designed to prevent oil from migrating back into the engine from the oil tank when the car is stationary. It is easy to install in the suction hose that supplies oil to the engine from the tank. It uses an internal stopper with a very light weight spring. When the car is parked, the spring keeps the valve closed. The spring is a super high quality mil spec part, but if it should ever fail the result would be a fully open valve. THERE IS ZERO CHANCE OF OIL STARVATION, EVEN IF THE VALVE WERE TO FAIL.
The early and late 911 valves are easy to install. You simply cut the factory hose, remove a section equal to the length of the valve body, install the valve as marked (Motor/Tank), and tighten the clamps. The special Oetiker double eared clamps provide constant tension and are far superior to a worm type hose clamp.
The 4-cam valve cannot be installed into the standard Carrera steel braided hose. It must use a special Cohline hose that is available from WR as a complete kit with the valve. The valve can also be purchase alone if you’d like to supply your own metric hose. The kit will accommodate all four-cam models including most race cars.
Four-cam cars, and all 911's up to 1989, have a dry sump oiling system. The oil for the engine is stored in a tank in the fender well and not in the crankcase as in a wet sump engine (like the 356).
A dry sump system has several advantages:
- Since no oil is stored in the crankcase, the engine case can be made smaller and the engine can be mounted lower in the car, lowering the center of gravity.
- Oil can be immediately evacuated from the crankcase with a scavenge pump, reducing oil drag on the crankshaft.
- A larger amount of oil can be carried in the tank, and controlled with internal baffling so that oil is constantly available even during hard cornering.
The disadvantage of a dry sump system is that it is much more complex. It requires a separate oil tank and the necessary lines. It also requires a two-stage oil pump for pressure and scavenges. Almost always the oil tank is mounted above or at the same level as the engine. This is the case with the four-cam and 911 models.
When the car is parked, especially for long periods of time, oil will migrate through the oil pick up hose, through the oil pump, and into the crankcase. When the oil level gets high enough the oil can then enter the lower valve covers, migrate down the exhaust guides and into the exhaust port. This is especially bad on the 4 cam engines with their large 11mm exhaust guides, and low exhaust valve covers. It’s not unusual for all pre-1989 911s and 4 cam cars to produce a cloud of smoke on start-up, especially after being parked for more than a few days. The newer, thinner, oils have made this even worse.
The WR Anti Drain Back Valve is designed to prevent oil from migrating back into the engine from the oil tank when the car is stationary. It is easy to install in the suction hose that supplies oil to the engine from the tank. It uses an internal stopper with a very light weight spring. When the car is parked, the spring keeps the valve closed. The spring is a super high quality mil spec part, but if it should ever fail the result would be a fully open valve. THERE IS ZERO CHANCE OF OIL STARVATION, EVEN IF THE VALVE WERE TO FAIL.
The early and late 911 valves are easy to install. You simply cut the factory hose, remove a section equal to the length of the valve body, install the valve as marked (Motor/Tank), and tighten the clamps. The special Oetiker double eared clamps provide constant tension and are far superior to a worm type hose clamp.
The 4-cam valve cannot be installed into the standard Carrera steel braided hose. It must use a special Cohline hose that is available from WR as a complete kit with the valve. The valve can also be purchase alone if you’d like to supply your own metric hose. The kit will accommodate all four-cam models including most race cars.
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