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View Full Version : KNocking Fuel Pump?



scottyz
10-13-2005, 06:17 AM
I just finished building a 383 small block chev. I put a Holley 327-11 mechanical fuel pump on the engine. THe engine specs and clearances are all well within range. I had a friend help me build the engine who builds high performance engines for a living with a reputable shop. I noticed a knock in the engine after breakin. Didnt sound like a rod knock. The knocking sound like every revolution of the cam. Started to probe with my stethoscope and found the noise to be worst at the fuel pump. I replaced it with a stock pump that was lying around. Noise dramatically decreased. I could still hear a very slight knock but still loudest from the pump. MY question is have you guys ever run into knocking fuel pumps? Are these Holley pumps junk?
What kind of mechanical pump would you guys recommend?

coolclassiccars
10-16-2005, 04:47 AM
i have had several chevy fuel pumps make knocking noises,stock ones,see if the arm is loose,also measure the fuel pump rod lenght,found some to be a 1/4 '' shorter,and don't know why.don't forget to lube the rod up good before you install it.good luck.hey, is it snowing up there yet?

qwik1320
10-16-2005, 06:51 AM
I had a Holley pump on my 73 and there was a pressed in screen inside the pump that came out of it's seat. Opened the pump up and there it was, rattling around... Made the car all but shut off when cruising down the highway. Junk, you decide. I have Carter pumps on my Camaros now.

scottyz
10-16-2005, 08:19 AM
coolclassiccars. Nope. No snow yet. Other than this week our weather has been awesome. Friday it was roasting outside. I put a new pump on the car and it is still knocking. I pulled the pump off and ran it again several times with no pump and cant hear knocking. Maybe very slight. I am wondering if there is a knocking that has to do with the cam that sends the noise through the fuel pump. The valves are all set properly. Car runs great. No abnormal valvetrain noise. I have driven the vehicle over a couple hundred miles since I finished the engine.I have been beating on it too and I would think the cam would have gone for a dump by now if there was a problem with it. Done 2 oil changes and cut the filter open and I 'm not finding any metal. Tried 2 different fuel pump pushrods and still no diff. Everything on the engine is within spec. I am beginning to wonder if the cam has a problem with the fuel pump eccentric.