I've got a question for the late Chevy gurus. I have a 250 that is making a ticking/thumping noise. It seems to be coming from the back lifter area, so I'm thinking its a bad lifter. I pulled the valve cover and checked for any loose rockers. Could there be a collapsed lifter that is still holding the rocker enough that it is firm to the touch? I rotated the engine so that I could be sure and check for slop during the compression stroke. Is there any other technique to diagnose this other than lifter replacement? I'd rather not throw the $50 at it without some assurance that I'm actually making an improvemnt.
I'm tending toward this because I've had similar experience with elderly Chevy and Pontiac v-8s where they had noisy lifters that couldn't be quietened with adjustment.
regards,
Leon
