lt1 head problems

There is a strange fast paste ticking noise coming from my heads at idle. I either think that it's a push rod or stuck lifter.
The car has been driven on a clogged cat for a while befor I figured out the problem. When i replaced my exhaust manifolds to shorty tubulars i started the car for a second with open heads. This is probably the reason for the valve noise or from the clogged cat?
Should I do some head work?

hard to check, only way i really know of, is to pull the valve covers and rotate the engine in incraments, checking all the rocker arms for propor lash. then once you reset all of them correctly, put the valve covers back on, and start her up and see if the noise is gone. if it is, problem solved. if not, check back and ill make another swag.

thanks I-Roc man

hard to check, only way i really know of, is to pull the valve covers and rotate the engine in incraments, checking all the rocker arms for propor lash. then once you reset all of them correctly, put the valve covers back on, and start her up and see if the noise is gone. if it is, problem solved. if not, check back and ill make another swag.

very good advice! start there first!