How should I clean my cylinder head and engine block contact surfaces before a head gasket change? There is residue paint from the old gasket on both the head and block side. Should I do it carefully with a razor blade or sand paper or perhaps use something non-abrasive like microfiber cloth with Brakleen? I believe both the heads and the block are made of aluminum but the cylinder jackets are stainless steel.
You shouldn't sand the block at all unless there is existing damage of some kind - but it really doesn't take much to damage, even a fine scratch can ruin the seal for the gasket. If you have to sand it, you will have to finish it to quite a fine grade and be very careful about keeping the surface relatively even/level.
If you are very careful, you can use a razor blade to scrape the old residue off the block - just remember that if you scratch it at all, you'll have to repair the damage (by sanding and resurfacing the affected area of the block). Many people use plastic tools (any kind of hard-edged plastic scraper) to avoid the possibility of scratching the surface.
Chemical gasket remover compounds are also available, which smell like death, eat disposable gloves, and burn your skin, but will chemically eat away any gasket residue. I don't have any personal experience with them, but for $10 or so for a tube it may be worth a try. If you don't need something as heavy-duty as gasket remover, you can try a solvent like varsol/paint thinner to help loosen the remnants.
Check out Jafro's video on his YouTube channel in which he shows how to scrape off the gunk accumulated on his head gasket prior to inspection.
He uses a long-handle scraper tool with razor blades to clean off the surface.
Brake cleaner will be wasted if you try to remove burnt-on gasket material with it.
Whatever cleaner you use, be sure to protect the cylinders, valves, etc. before you start. I stuff the cylinders tight full of clean rags and cover the valves with a thick rag. Also, I've used oven cleaner (Easy-Off) to remove baked on oil and grease from steel surfaces, and it doesn't seem to react with the metal; but you should try a small amount on a clean area first and check carefully for any sign of metal residue on the rag or sponge you use to wipe it off, and STOP if you see any. Pretty effective on old cork gaskets on a radiator core flange. Doesn't seem to harm the brass.
