MR. Clean: Prepping An Engine Block For Assembly

Although it is possible to build an engine almost anywhere, a clean environment is a must. In my workshop, I stop any activities that create dust and grit. For example, if another project requires grinding, then I either move the operation to another spot (for example, perform the grinding outdoors or in my tractor garage) or figure out another time to get it done.

You’ll also need a workbench. I have one in my garage, and I’ll be the first to tell you it’s too small and it seems regularly cluttered. You have to clean it off! If you don’t have a good workbench, a sturdy folding table will suffice (places like Costco sell inexpensive jobs). Once the clutter is reduced, I regularly cover the bench surface with paper. Some folks use good old-fashioned newspaper. Others use butcher paper. I use white poster board, because it’s easy to spot little parts and it’s a wee bit more immune to oil spills than newsprint.

When it comes to using tools, I always make it a practice to clean them after use. I’ve found a quick shot of brake cleaner (aerosol) and a wipe down with a clean paper towel goes a long way toward keeping the project clean. It also makes it more enjoyable to work with the tools.

Cleaning the Pieces…

When it comes to assembling an engine, one of the biggest mistakes a novice can make is to contaminate the components. Any piece of grit that turns up during the assembly process can (and regularly will) scratch internal surfaces such as the cylinder walls or reciprocating components. I’m convinced contamination is one of the leading causes of premature engine failure. Because of this, once the parts return from the machine shop (obviously something you can’t do in your own garage), they must be thoroughly cleaned and kept clean during the entire assembly job.

So how do you clean it? It’s actually rather simple. Once the machining operations are complete scrub everything with hot water and good old-fashioned liquid dish detergent (car wash detergent works too). The catch here is, you have to access all of the oil gallery holes. That means the block gallery plugs should all be removed (as is regularly the case with blocks that have been through a machining process). Several companies offer brush kits. I acquired mine a long time ago and it included several different brushes designed to work in engine oil galleries. When shopping for a kit, make sure it has some extra-long brushes for use when scrubbing oil galleries adjacent to the cylinder block lifter bores.

The old backcountry garage I used when these photos were taken wasn’t blessed with a paved driveway or even a cement apron in front of the overhead doors. It was simply gravel. To circumvent grit accumulation during the wash cycle, I always place the block and components being cleaned on a rubber mat. An old pickup truck tailgate mat or bed floor mat works perfectly. Before going any further, you have to make mental note: Once you start cleaning something like a cylinder block with soap and water, you can’t stop until the job is done. The old saying about “rust never sleeps” truly applies here. You need time to complete both the wash and dry cycles!

First things first: Hot water and soap is mixed into a bucket and the pressure washer is hooked to a hot water tap. I use a conventional car wash scrub brush for the initial cleaning. Once that’s done, I remove the cylinder block main caps and go through all of the oil galleries with brushes. Once you figure everything is clean, start all over again and rescrub the entire works.

Once the second wash cycle is complete, turn on your pressure washer. Every nook, cranny and oil gallery should be blown out. It’s my practice to continue spraying hot rinse water until the water comes out clean. Then the block is moved (flipped) and the hot rinse continues again. Repeat at least once more and you’re ready to dry the works off.

I’m fortunate in that I own a big 220-volt, 5.5 horsepower compound air compressor. It produces copious quantities of air. No matter what type of compressor you own (or rent), be sure the regulator is set to provide something in the range of 100+ PSI. Snap a blowgun attachment into the air hose and basically, let the compressor rip. What you really need to do is to blow as much water off the engine as possible. And the quicker the better. Use the air force to blow all of the water out of the oil galleries, and don’t be timid. There will be plenty of water moving around, particularly from the exit points of smaller oil passages.

Once the block is blown dry, you must oil all of the machined surfaces. There are a couple of ways to accomplish this: A clean rag soaked in clean light oil (for example 10-30) or automatic transmission fluid works. So does a light mist of WD40, followed by a wipe down with clean shop towel. WD40 will naturally displace water, so it works in your favor. I always clean the machined surfaces until the shop towels show absolutely no trace of dirt. The preferred towel here is actually a roll or two of paper towels. I prefer the mechanic style blue jobs since they don’t tear or shed as easily as kitchen towels (Costco and other discount houses sell them in bulk).

I treat all of the internal engine components to the same cleaning process. Once clean, I place the various bits into fresh plastic bags (freezer bags work) and zip them shut until I need the respective parts. When cleaning items such as a crankshaft, you’ll note that small engine cleaning brushes go a long way toward getting into the various oil passages. Be careful not to nick any machined surfaces.

After the block is spic and span, it should be wrapped up. While jumbo garbage bags work, they’re usually flimsy. I prefer to use an engine storage bag. Several companies, including offer large 4-mil plastic bags designed to protect racing engines against dirt and moisture. They’re large enough to accommodate an assembled big-block - even one with headers in place. These sturdy covers are ideal for storing and transporting race motors too. And that means they’re perfect for protecting your block while you’re not working on it. I always wrap the block or engine immediately after work on it has ended. Remember, the main idea is to keep contamination to a minimum.

Scrub all of the accessible surfaces with soap and water. Liquid dish detergent works perfectly. So does automotive car wash soap. You’ll go through a lot of soap and water. The pieces need to be clean. Once clean, remove the main bearing caps and clean them separately (they’re not removed in this photo). Removing the caps allows you to access the main bearing oil galleries.

Once the outside is initially cleaned, you can scrub the internal oil passages. The extra-long brushes are designed so that you scrub the entire length of the lifter oil galleries and in the case of this engine, the main oil gallery.

Once rinsed a number of times with hot water, you can dry the works off. Compressed air and lots of it is your friend when it comes to drying engine hardware. I typically wipe dry multiple times using either WD 40 or engine oil (or ATF). The text offers more insight.

Continue to wipe the block down until the shop towels no longer show any traces of dirt. Paper towels are better than cloth for this task, and I prefer these blue mechanic towels.

Your finished cylinder block should look like this when you’re done. In this example, the water jack core (soft) plugs were installed when the block was CNC machined. Remember, spotless is the operative word and you really can’t get these pieces clean enough!

Other components such as the main caps, crankshaft, connecting rods, pistons and wrist pins also need cleaning (using the same process as the bare block). The crank has oil passages machined into it too. Don’t forget about them.

When you’re not working on the various engine pieces, wrap them tightly with plastic. In case you’re wondering, I generally try to keep a clean oil-soaked craft paper on the outer machined surfaces (inside the bag). This example is a paper called “Armor Wrap”, but any clean paper will work.