Pull the valve covers off and check to see how far valve springs are going down, it may have a bad camshaft in it where a lobe is worn down. Then check pushrods for being bent and worn on tips. If cam is bad replace cam and lifters and use something similar to stp or graphite grease on cam lobes and lifter bottoms. To check for bent pushrods roll across a flat surface like a table.
Friday, December 18th, 2015 AT 9:34 AM