What is the best way to clean up a used motor?
so that I can give it a fresh coat of paint before installing.
Thx
Bill

Get some Simoniz Brake cleaner in spray cans. I get it at Ollie's Bargain store.

Scrape the thick stuff then use mineral spirits and a parts cleaner brush then air pressure or rags then brake cleaner.

Rebuild it, works every time.

that way when it comes back from the machine shop, you will
have a fresh clean slate to work with.

Pressure washer, soak down with degreaser spray then pressure wash again.

All of these are good ways. I prefer to scrape off the thick sludge, then use brake cleaner (high VOC, non-chlorinated type) or paint thinner. The best solvents (in either case) for oil/grease are heptane, hexane, toluene, xylene, mineral spirits, and VM&P naptha. Acetone doesn't clean grease/oil very well BUT it is very good at removing water if you go the soap/water/power washer way before painting. Acetone can be a paint thinner OR the main ingredient in "low-VOC" or "ultra-low VOC" brake cleaners.

Dollar store oven cleaner it has a nice lemon scent if you choose the scented one. Wash it off your skin quickly it you get it on you

I bought a gallon of Purple Power from Walmart and put it into a spray bottle. Cheap and does a good job, but watch out. That stuff will burn your hands.

I just did one this week. Here's what I did In a nutshell:

Subject: 1956 354 Hemi

Condition: Stock & ran good when pulled 10 years ago, stored indoors

Plan: To use it as one of my carburetor testing mule engines

Goals: To tear it down to the bare long block, hand clean and de-grease the internals before adding new required replacement test parts, add a new gasket set, and de-gunk and paint the outside to look nice and clean.

Cleaning tools & materials: Steam cleaner, parts washer, Mineral spirits, Acetone, Simple Green, gasket scraper, screw drivers, plastic bags, 90 degree air die grinder with 2.00" Rolock pads for cleaning.

Tools: Various hand tools, brass hammers, drifts, tap & die set, sockets, end wrenches, pliers, pry bar, harmonic dampener puller, oil pump pre-lube priming shaft, assortment of pans for fluids and small parts, engine hoist, engine stand, rolling tool cart.

Parts & materials: Engine tear down gasket set, Hot Heads cast aluminum valley pan cover, intake manifold with single 4, dual 4, and six pack tops, BB Chevy water pump adapter & timing cover kit, rear head water block offs, water cross over tube, thermostat housing, 340 harmonic dampener, Cloyes Tru Roller timing chain set, engine paint, engine oil, engine moly based engine pre-lube, engine break in zinc oil additive.

Steps:

1.Remove as many external components as possible to the long block (leaving intake manifold, valve covers, oil pan, and valve covers). Stuff all holes with rags and duct tape to cover from water entry. Steam clean with hottest water possible. After steam cleaning spray down and let soak for several hours with mineral spirits, use a plastic bag to encapsulate engine to hold mineral spirits in and wet. Next day, steam clean it again, let it dry, and wash it down by hand with mineral spirits again using a scraper and screw drivers, etc. to chase down stubborn/thick grease areas.

2. Mount engine on an engine stand, remove valve covers, oil pan, intake, etc. steam clean the insides of the larger parts, put all small parts, nuts and bolts etc. into parts washer, use individual containers to keep them sorted.

3. Hand clean grease and gunk from the engine internals best you can. I used mineral spirits to wash everything down and out the bottom, a couple gallons worth and a plastic bristle brush to scrub it all out. Rotate engine as you clean to get as much as possible. R&R timing chain and gear set. Set top dead center on #1 cylinder.

4. Loosely replace intake, oil pan, valve covers, and tape off all holes to the internals. Use 90 degree grinder with Rolock pads (like red scotchbrite) to go over and clean all of the cast iron, heads, sides of block, etc. until bare clean metal, use picks and screw drivers to get the cracks and crevices clean of grease. Wash down all externals with acetone soaked sponges or rags (wear your PPE!). Paint engine block and heads with engine paint.

5. Add moly lube to all internal wear surfaces with a brush, rotate engine as you go, especially cam, lifters, areas between rod, and crank journals. Pour small amount of engine oil over all surfaces while you rotate engine by hand.

6. Prime oil pump with a drill motor until oil comes from rocker shafts.

7. Install fresh gaskets and button up the valve covers, timing cover, oil pan, intake, etc.

I'm still not done with mine, still awaiting a few small parts then I'll mount it on the engine test stand and finish it off before the first fire up.

Nice! So good it looks photoshopped