I have a 1970 Oldmobile 442 with a 455 CID engine. It overheated on me a year ago and has since made a clacking noise that sounds like it is coming from the valve train. I have replaced the lifters and push rods and the noise seems to have decreased a little. I believe what happened when the engine over heated it loosened some gunk in the passages and now one or more are blocked and the lifters are not getting enough oil. I have run motor flush through a couple of times and I am driving once a week to get engine up to normal operating temperatures in the hope that it will clear the blocked passages. Any suggestions? Thanks.

 

Have you checked the lobes on the cam to make sure they are in specs?

 

If the engine has never been rebuilt you may have some worn rocker arms or even some burnt valves, they can cause noise too.

 

thanks for both of your suggestions. I have not checked the cam lobes but I have changed the rocker arms. Another reason I believe the oil passages are blocked is after I changed the parts I left the valve covers off and very little oil was coming out of the push rods. just a dribble. after I used the engine cleaner a few had oil shooting out, which I am assuming is more normal. Again thanks for your suggestions.