Cam Install... Read this first.
Mar 28, 2008, 01:14 PM
#48
Tapping is usually because the lifters aren't fully extended since they aren't completely filled with oil.
The reason for bleeding them is because once you remove them, they extend FULLY once you remove the stock cams and allow them to expand to their full length once you remove the tension and they become hard as a rock. When you reinstall them they can over extend a valve and get hit by the piston, bend a valve stem, score the cam journal, bend the camshaft or damage the lifter itself. Bleeding them releases the built up oil inside the lifter assembly. WHen you start the car afterwards, the lifters are actually too short and you will get ticking at the beginning usually. The engine will feed oil up to the lifters to refill them but you need to get the oil pressure high enough to get it into the lifter. Thats why you need to do the 3K rpm method.
Slowly rev the engine from idle up to 3k rpm(gradually do this so it takes 15 seconds to reach 3k RPM), then quickly release the gas pedal so it returns to idle. Wait 15 seconds and repeat. Do this until the ticking is gone, can take more than 10 times for some people. This fills the lifter just enough to create the proper tension between the cam and the valve.
Hope that helps
Last edited by Jack_of_Trades; Apr 11, 2008 at 09:56 AM.
