MrCJ

I recently swapped cam (big and lumpy), springs (K-motion 775 doubles), pushrods (7.4), ...

At first startup, all sounded good, then I got a horrible knock (like a bad lifter - very loud). I checked preload, everything seemed good.

I took the car for a very short drive (just around the block), and the noise suddenly stopped, but it sounded like I lost a cylinder at the same time.

I took the valve cover off, and noticed that one of my lifters appears collapsed, and the pushrod isnt even touching the rocker. But the engine is much quieter!?!

What could cause this to happen, and so quickly after a swap? Car has practically not even been driven...

Jontall

Did you thoroughly clean the inside and outside of the camshaft before installing it? They are usually full of metal shavings and cutting oil debris (in the center) from machining; the pushrods too.

MrCJ

I sprayed brake cleaner through the cam, and on the outside, and it seemed clean (nothing unusual came out). I then covered it in sticky assembly lube.

Is there any chance of getting the "collapsed" lifter back to life? I thought that they had a spring, which should push it back up even without oil, but I don't have lots of experience with LS engines.

Che70velle

iTrader: (6)

You prolly should have shut it down when you heard the “horrible knock”.
I can’t see why you would have kept running the engine, or even thought of going around the block in it with it making noise.
I’d pull the head and take a look at that lifter and corresponding lobe. Go ahead and cut your oil filter apart and inspect as well.