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question on oil pump replacement


Well-known member
Apr 17, 2001
Loxahatchee, FL, Palm Beach co
question comes up, can you replace the oil pump while
the engine remains in the corvette,

Ive replaced BOTH oil pumps alone and oil pumps and oil pans several times, on c4 corvettes, both L98 and LT1s while the engine was still in the car and on the motor mounts,its fairly easy to pull the pan and replace the oil pump on a C-4,place the car on a level concrete surface and on 4 jack stands one on all four corners at about a 18"-22" height so you can work under the car safely,
the diagonal braces to the k frame usually need to be temp removed and the coolant lines under the oil pan disconnected, the starter usually needs to come off, but generally the only trick is the crank needs to be rotated slowly once the oil pans free to alow the counter weights on the crank to clear the front lip on the pan because you can only lower it slightly due to the cross member. make damn sure the oil pump pickup is 1/2"-3/8" off the oil pan floor once its installed and BRAZED or welded or bolted in place on the pump
now what does quite frequently happen is that the guys installing a high volume oil pump just swap out the standard pump, reinstall the stock or simular pick-up and bolt on the pan with the pick-up in the stock possition on the oil pump. the stock pick-up is mounted about 3/8" off the pan bottom,the high volume pump is normally equiped with impeller gears about .3 inches longer than stock, the high volume pump body is that much lower in the pan, resultting in the pick-up being only about 1/8" from the pan bottom. the result is that on a normal chevy oil pump pick-up this leave a space of about 1/8" x 2.5" for oil to flow into the pump. at low rpms this works but as the rpms climb the pick-up that can,t get any oil to pump cavitates as it spins and fails to pump oil, result oil pressure drops untill rpms are lowered no matter how much oil is over the pick-up. simply checking to make sure that anout 1/2" of space is under the pick-up when the pan is installed cures that problem (a simple trick is to weld a 1/2" thick nut to the oil pump Pick-up base and test fitting the pan BEFORE WELDING THE PICK-UP TO THE PUMP BODY)


I might add that when welding/brazing the pickup tube onto the pump you should remove the relief valve and spring assembly. If you don't sometimes the valve gets stuck in the bore and you will have problems with the pump. Don't ask me how I know this!!


PS: Be sure to re-install when the pump body cools down!!

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