Classic/Antique Car Repair: pontiac valve adjustment, hydraulic lifters, valve lifter

Question
Sir, my engine has been slightly modified, but i hope you might have some thoughts on this. I have a 1968 400 pontiac. The only real change made to it was a Crane HMV 280 cam and locking valve adjusters, and crane hydraulic lifters. It was put in several years ago, valves adjusted per the instructions. it runs fine but over the years, valve train noise gets worse. I have readjusted the valves and the noise goes away for a while, but comes back.This car is very rarely driven and with hydrualic lifters i shouldnt have to adjust them anyway. I have good oil pressure. Any thoughts on what the problem could be? any help would be reatly appreciatted. Chris

Answer
You're right, I have no experience with non-factory cams, so all I can do is make some guesses.  

If all of the valves are doing this, it is a mechanical problem for sure.   One thought is that maybe you have extra heavy valve springs or higher than factory lift, or a more aggressive lift profile, and that is causing rapid wear on the push rods or the rocker arms, or the retaining studs that hold the rocker assemblies into place are working loose due to the extra stress.

If only one or two valves are doing this, there is a possiblity that some crud was introduced into the engine when the work was done, and you are having valve lifter problems because of that.  If you think that is a possiblity, search for a product called "CD-2" oil treatment - it is a powerful solvent and detergent additive, which sometimes does magic on noisy lifters - often curing the problem while you pour it in the crankcase!

Beyond that, I have no ideas - if you're positive your oil pressure is OK.

Good luck!

Dick