When you guys get your clean engine block back from the machine shop and get ready to paint it, do you use an etching primer first or just the high temp primer and paint?

I didn't use primer. Just wiped it all down with acetone and sprayed it with hi-temp Chrysler Blue. Looks great after two years and 5,000 miles.

I wipe down the exterior of the block with paint thinner to clean any oil and assembly lube off the exterior, then I spray it straight with Eastwoods 2-part catalyzed ceramic engine paint.

I spray it down with lacquer thinner.

Spraying it down with lacquer is fine. But I would put an epoxy primer on it before I painted it. It holds up to temperature, helps the paint hold up much better by providing a great foundation. It also helps fill in the micro imperfections on the areas that have slight casting flaws.

I wiped mine down with lacquer thinner, then used primer, then painted a few coats. Still looks great a few years later.

I used to use lacquer thinner. I had a few problems later on with the primer coming off. The lacquer thinner drys to fast to remove all the oils. Use prepsol with lots of rags until they come off clean. Then we spray with single stage urethane. There are other methods but I like a very durable shiny engine. Don't be afraid of Bondo either. We have a bondoed cross ram that with paint that looks like the pic below, 15 years old.
Doug

No Indy logos, bondo