Priming the rebuilt engine question

If it’s a got a roller cam, I don’t see it being an issue. A new unbroken in flat tappet cam though, I think that would be a different story

^^I agree^^ You are supposed to pre-lube bearings, pistons, cam, lifters when installing and a few seconds at slow speed on a drill will not hurt.

But with anything with a distributor, it's "usually" pretty easy to get or create a priming shaft. and that method is better

On a side note I always start with the filter REMOVED, and prime for just a second or two. Oil should immediately come up from the pump. This action removes the head from the pump and makes it easier to prime the pump. Then install a pre-filled filter, and with a hose, now get oil to the sender port, and then replace that with a gauge. You can FEEL the pressure on a drill because with that port plugged and oil pressure "up" the drill will pull very hard. A 1/2" drill is better

Then watch for oil out of the rocker shafts, and with a drill you will have to turn the crank so the cam oil holes line up