I have a 78 280z with 115k miles....it has not been driven much in 20 years.  My son bought  it 4 months ago.  The oil had been changed when he bought it and we have now changed it 2 more times to make sure it cleans itself.  A professional did a compression check that showed 150 in each cylinder. The pro also said we might have a ring leak after blowing compressed air into #1 cylinder.

All this led me to add Lucas oil stabilizer in with the last oil change yesterday. After driving it 20 miles there was a distinct valve clatter louder and different that what had been usual before this oil change.  It sounds great cold but after warming up the heavier clatter starts.

Cause and effect is something I pay attention to. I am considering giving it a few days of light driving to settle down. I am also considering draining it all back out and putting clean oil and a new filter back in. 

Also I put a wix filter on this oil change when all previous I used a Fram.

Any thoughts?

Thanks

When was the last time the head got a valve adjustment? If it's not been done in your ownership, i would start there.

agree Heyit!

No idea the last time it was done.  i have not done one before but plan to do it Sunday.

Adjusted the valves and it cleared up nicely.