Tim,
I would not worry a bunch at this point. I suspect you will drain the 30 weight out after you have seated the rings. If this was my car, I would use that oil for a 200 to 300 miles.
If the slight tappet noise is only during the frist couple minutes and goes away, live with it to the first real oil change a 2,000 miles. If it continues to worsen slightly, then talk to the engine builder about the push rods. As I remember you can get 1/32 and 1/16 inch longer push rods for the non-adjustable FE motors. If you isolate it, you can try the 1/32 longer push rod.
It may be a tappet that is a little grumpy when cold and will soon get better with use. I have used 20/50 Castrol for years. And the Castrol full synthetics. I have went to lighter weight Purple Royal synthetic in both my motors now that I push both very hard. VERY HARD!!
I assume this slight noise is when it is cold?
Rob
Update on the tappet noise Rob;
after about 600 miles, it was still present (tho intermittent). Oil pressure and engine performance was never a problem... I tried 20/50 after 400 miles or so - still noisy, added some Marvel Mystery Oil (to wake up sleepy lifters) - same... I researched some classic T-bird forums and found a lot of discussion about the same issues. I even removed the fuel pump and listened after reading that a worn pump can make the same noise...
I finally changed back to 10/30 Castrol and using cardboard gutters made from valve cover gasket boxes, ran the engine without covers to isolate the noise. The heads were lubing beautifully and everything seemed in order, but several push rods were noticeably loose, though not at all bent.
Per your advice, I went to "auto parts" and found there are indeed 3 sizes of push rods for the 390 (?) I bought the set 1/32 longer than what I had, put them in and now everything is quiet as a mouse! I can still spin them in place after some running, so there appears to be no undue stress with regard to the lifters.
Thanks Rob! We'll see what happens from here
