a rocker hits a valve cover?? I just installed a cam with a 632 lift and have been trying to get it to idle, all of a sudden I hear a loud poping metallic sound, maybe once every 20 seconds. like the crazy drum sound on metallicas St. Anger album (closest thing I could think of )

took the covers off and there are some small knicks on the drivers side, but doesn't look like a LOT. was horrified that it was a PTV issue initially

EDIT: NOT the rocker/cover clearance! I'm lost on this one as well as quite a few of my mechanic friends... look down for more details

 

what kind of rocker arms are U running?

 

you're just not up on your luck lately dude!! if its only once every 20 seconds, then thats kinda odd. the only thing you changed was your cam? also curious type of rockers you are running.

 

rockers are yella terras. I found where they were hitting the valve covers, clearanced that and it is still doing it.

I have a totally new setup. 408 with a 246/250 .632 cam, crane double springs and Milner lifters. it doesn't do it on initial startup, maybe after 30 or 40 seconds it will do it every 10-20 seconds. kind of like a bongo drum sound if that makes any sense... sticky lifter maybe???

 

I dunno man, it doesnt make sense that a rocker would just hit the rocker every now and then. It should peak just as high every time. Maybe its just not making the sound loud enough for you to hear every time???

 

Well, you can put a spacer under your rocker covers and connect all the coil packs, fire it up and listen.

 

it is NOT the rockers. I clearanced them and it still does it.

 

Use a mechanics stethoscope and listen to the top of your valve covers, then listen on points of your headers, that may help pinpoint where the noise is coming from.

 

Do you have the correct Pushrod Length?

 

well, the preload seems correct, so I think so.

 

no bent pushrods... have the rockers off. it now makes the noise when I just turn the engine over with no ignition. it did NOT do this when I was initially priming the oil pump.

 

also hand cranked the engine over and couldn't tell any hangups..

 

revoved rockers from passenger side and turned it over. no noise...

 

We had a similar problem to my friend Beau's 383, it turned out to be a Crank Clearancing problem. I'm not sure what yours could be though.

Things that come to mind are

Wrist Pins
Crank
Lifters
Valve Lash

 

I did replace my Comp R's with Milner lifters. lifters are just a drop in replacement, right? what is there to screw up with a lifter install?? I'll take the heads off asap and check them out.

 

I didn't think you had to pull the heads on these motors to get to the lifters? I thought you just took off the intake manifold?

Anyway... I have heard that lifter bores sometimes need to be machined because they sometimes lose their perfect cylindrical shape. Now.... I am going out on a limb here, but possibly the lifter bore has lost its perfect shape, and these new lifters are fot a certain shape, and thereforw, every once in a while, one is getting stuck and leaving a valve open and a piston is just barely hitting it. After all, these are what they call "interference" engines right.... meaning that if a valve is left all the way open that when a piston reaches TDC they will hit.

Let me know if I am wrong on this one or it is a stupid idea.....

 

The heads must be removed. They are located under the heads unlike traditionaly SBCs where the lifters are accessbile under the valley cover plater.

 

jeez, I feel like a moron... pulled the passenger head off and 6&8 had not ever fired.... guess what was wrong