B20 engine and head rebuild
 

Just started to dismantle my B20 engine for rebuilding. What is the best way to get rid of the oil, grease and old paint on both ? And is it best to re-paint the block and head before or after the rebuild? Many thanks

A lot of the larger machine shops have what is commonly referred to as a 'hot tank' for cleaning parts. That is the process that I would recommend as it avoids dealing with a bunch of nasty chemicals and the associated (ethical) disposal problems.

For painting, definitely do it after any machine work has been completed otherwise it will get banged up. If it has been hot tanked prior to the machine work, all you will need to do is a final surface degrease. Brake cleaner should suffice. I would also recommend that you etch the external surface prior to painting to improve adhesion. I think POR 15 metal prep will work for this; but, there are probably other products.

Depending on how greasy it is, I would close all of the openings, spray on a degreaser and power wash it as my first step.

I would continue to clean it as I disassemble. I would also pull whatever oil galley plugs and core plugs I felt comfortable with and wash as best I could all the debris out of the engine. Get a bunch of wire and plastic brushes to reach deep into all of the oil galleys and anywhere else rust or debris can accumulate. Only then would I take it for a hot tank treatment and crack testing. See note below about using hot soapy water.

In today's anti-pollution environment, I'm not sure all of the hot tanking is equal, but I think the goal of hot tanking is to remove the rust not so much the oil and grease.

When you take the block in for hot tanking, you might also take in the crankshaft for crack testing and balancing as well as the flywheel for balancing. You might also take in the connecting rods for cleaning, rebushing and crack testing. I would also have the machine shop set all of my clearances - pistons, rods and main bearings, possibly camshaft.

Once the engine came back from the machine shop, I would test assemble, making sure all of the clearances are correct. Trust the machine shop, but verify. Once I've test assembled the engine, I would disassemble, and then wash the block and the head in soapy hot water, using all of those wire and plastic brushes, until the water was quite clean. In my limited experience I've had to wash the block and head at least three times after the components were hot tanked and returned by the machine shop.

When you wash with soapy hot water, blow immediately everything dry with an air gun and spray everything with WD-40 to prevent flash rust. On big surfaces finished such as the deck or head, if you are uncomfortable using WD-40, use motor oil and spread it over all surfaces.

I usually paint the motor after assembly. Of course, some of the peripherals such as the alternator, can be painted before mounting.

I don't know about the regulations in the UK (or other countries) but here in the Netherlands the washing machines at the machine shops are not allowed to use the chemicals they used to use. In my experience items don't come out as clean as they could. This is very unfortunate as using this service used to be ideal.

For my last three engine clean ups and repaints I've resorted to using products like Gunk (I think that's available in the UK) - here in the NL I last used mountain bike cleaning products and brake cleaner. The available degreasers here are often water soluble products whereas the brake cleaner usually isn't (!) - the brake cleaner will evaporate...

My personal experience of the POR15 degreaser was that there are better products available here in the Netherlands - I don't wish to "be down" about particular products as I often find that what is available locally is different for different parts of the world - meaning "you can only get what is made available for you"...

I just started refreshing an engine. Two seasons and about 26 hours on it.

Unlike the lump in the Volvo, the block is quite clean, and initially I'm using kerosene as a degreaser/solvent.

I won't hot tank this engine and I still haven't decided whether I will break it down far enough to wash the block or the head. If I hone the cylinder bores, however, I might need to.