I have a 1979 301 pontiac engine in my 1954 chevy belair.
The engine starts to produce a ticking sound at about 50 mph., like a ticking valve. It only is there when I am coasting or hitting the throttle and it is related to engine speed. When I take the foot off the pedal, it is gone. When I hit the throttle again above 50 mph , it is there again.

When I abuse it from 0 tot 50 mph , there is no ticking sound.

It has nothing to do with the converter or tranny, because I swapped them recently and the noise was there before and after.

When I let the engine rev up from idle to max in neutral , there is no ticking at all.

I checked for loose rocker nuts and checked ing. timing.(12 deg. with strobe light on idle rev)
I found out that all BUT 1 valve pushrods are turning rounds when the engine runs.(valve covers removed)

What could be wrong? Maybe a valve lifter?

Thanks,
fred,
netherlands.  

Fred, what you describe sounds like a case of spark detonation, occuring under light throttle or cruise. Try disconnecting the vacuum advance or backing down the base timing a few degrees and see if it makes a difference. Also if you are using the original carb and intake, is the EGR valve connected and working properly? Often a non-functioning egr valve will cause pinging due to the carb being calibrated to work with egr, the mixture is too lean and causes the ping.
Steve  

Thanks Steve, I 'll give that a try.
The intake is stock, the EGR and the carb mounting plate are gone, the carb is an edelbrock 1405 sitting on a handcasted 1 inch thick adapter/spacer , and I made 2 sets of headers for it , ending in  2,5 inch pipes with cherrybombs .
I will get back with the result....
fred  

Thanks Steve, I 'll give that a try.
The intake is stock, the EGR and the carb mounting plate are gone, the carb is an edelbrock 1405 sitting on a handcasted 1 inch thick adapter/spacer , and I made 2 sets of headers for it , ending in  2,5 inch pipes with cherrybombs .
I will get back with the result....
fred  

Hi Steve,
I tried all kinds of basic timing : 12 as it was, and 8 degrees, 4 degrees and 0 degrees , but no difference whatsoever. I also tried different oil viscosities , from 10W30 to 20W60 , to see if there was a lubrication problem, but still no luck.
Any other ideas?
thanks,
fred  

did you check the timing chain for play? if not do so remove the distributor cap while watching the rotor turn the crank by hand see if theres any play between the two you might have a worn chain