Hey guys, just bought a 1970 (at least that's what the block is) 350 for my Trans Am project. It was rebuild totally stock (heads too) and has ~500 miles on it since being removed and sold, as the seller's frame was rotted pretty badly. It looks like he was just running synthetic Mobile 1 through it, but should I just change it to more of the same, or use a break in oil?

 

If it's already been broken-in (500 miles), no need for break-in oil, but
I do like to run a zinc additive with flat-tappet cams. I would definitely prime
the oil pump before firing it up...

 

Why the zinc additive? And I'll definitely prime the oil pump, can't have that failing, thanks for the heads-up.

 

For the cam & lifters, which most likely, are not roller.

If it DOES have a roller cam, then regular Mobil1 is fine.

 

The story - short version.........
Zinc and phosphorus are what flat tappet camshafts & lifters have relied on to survive for 70+ years. Those are the anti-friction additives. Starting in the 80s, the EPA mandated that the oil companies begin removing the Zn & Pho additives because TRACE amounts would make it by the piston rings and shorten the life of your catalytic converter. So in their great wisdom, they made the oil companies keep reducing the levels at every new formulation (IIRC, SG was the last good oil) without telling anybody. Camshafts & lifters started failing widespread. So the federal government, in order to try to guarantee 100K miles for your catalytic converter, essentially removed all the good anti-wear additives in your motor oil. Now your vehicle sits in the junkyard with a blown engine, but the catalytic converter is just fine.
Any engine you have with a flat tappet camshaft needs the additive. Or read the bottle of oil you are considering to make sure it has the proper levels of Zn & Pho. Personally, I use the additives because then I know it's in my oil. Here are 2 additives:

 

Lucas hotrod oil should do the trick. Works great for flat tappet cams

 

I didn't know any of that, thanks guys!