I'm getting ready to paint my bare engine block. I plan on cleaning it well with laquer thinner and then soap and water. Do I need to use a primer? If so what kind? I'd like to just paint it with spray cans.
I use a clear primer. I think it's called XIM Flash Bond and it's an adhesion promoter for enamels, etc. I've used it several times on blocks and other parts and it seems to help the paint from chipping and flaking.
Since your block is fresh (and clean) ... hit it with good ole soap and water, blow it off with compressed air, then follow with some lacquer thinner and another shot of compressed air in the nook and crannies. Paint it the color of your choice witha high quality Engine Enamel rated for a temperature of at least 500 degrees.
You could go with a primer or more exotic extremes if your budget permits ... but I think for a driver you will be very happy with the results.
I've been painting engines with rattle cans forever. From now on its going to be real paint out of a real spay gun, you can prep, clean, scour, and brush till hell won't have it, but spray cans just ain't up to the task of a really great looking engine. I thought my last and most involved attempt was looking pretty good, till I was over to a street rod buddys house the other day. He had just gunned 2 motors for a couple of his cars, and they just were outrageous, no more spray cans.