I changed the rockers, changed the lifters, changed the pushrods and I still get this nasty clacking noise. Its very very quite at idle, but very audible the minute it goes past 900 rpm. I recently installed a cc306 and it was running fine for 2 days. Oil pressure is extremely good, 60 psi at cold, 27 at warm, no fluctuaction what so ever. I hear it mostly on the drivers side and I can't figure this out, I thought at first it was the lifters, changed those, changed the pushrods, and now the rockers and its still there. It doesn't sound like a rod because its coming from up top. All the rockers are getting really good oil and it smokes the hell out of my engine bay if im revving it (oil gets on headers). I've had people come by and look at it and they say it sounds like valve train. My father in law said it might be a cam bushing but I don't this LT1's have cam bushings. I havn't driven it since it has happened but when I did I could feel vibration in my clutch pedal. When I pulled the lifters I cleaned my hands and put some oil on them and stuck my fingers in the lifter valley's to check the cam lobes and all felt great to me. Im stumped on this one guys, can someone tell me what is going on?

 

Did you look at the cam lobes? Almost sounds like a wiped lobe to me. Even if it's a roller cam. A 306 is still on a cast core and that could happen.

Bret

 

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You can't tell if the lobe is wiped by "feeling" it. Measure how much each lifter travel's up out of the lifter bore. I'd try using a 6" machinest ruler resting on the top of the lifter bore. Do the intakes and write down your numbers then do the exhaust lifters and see what you find.

 

Guess the cam is coming off then. Would there be any evidence of metal if it got wiped?

 

Well I pulled the cam and it looks like one lobe has a little more wear than others, i'll post a pic tomorrow and maybe you guys can tell me if it looks normal for a 306, I honeslty cannot remember how it looked before I installed.

 

Did you measure the difference in lift at the lobe from the good to the bad lobe? That would tell more than the sight of the lobe unless its REALLY UGLY

 

Its not too bad, infact, dont think there is anything wrong with the cam. Any way to check the cam bearings and replace them without pulling the motor?

 

Not really.

 

seems to me like it would have made more sense to measure the lobe lift than to pull the cam . other possibilities could be a collapsed lifter or a broken valve spring

 

Wow, thanks for non-helpful information. Already done, lobes are fine, the bearings are copper and cam bushings look scratched on the front and rear. Anyway I can replace the cam bearings while the engine is still in the car?

 

you said you replaced the lifters if you wiped a cam lobe before you replaced them you would have seen damage to a lifter