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First step to engine assembly: Cleanup and prep

For the beginner, assembling an engine at home is most certainly an intimidating prospect. There are plenty of parts that have to fit precisely and there are plenty of dimensions that must be checked and double-checked (and some triple-checked). There are all sorts of seemingly “foreign” pieces that somehow have to work in perfect harmony. For the beginner, it seems like an impossible task to put it all together. We’re here to tell you it isn’t.

Engine assembly is like any other major project. There are various parts and subassemblies that are completed first, and then each “builds” upon the last. Building an engine at home is a skill just about anyone can learn. Sure you’ll need a good collection of specialized tools (we’ll help you with tool selection throughout the entire series), but the reality is that anyone can assemble an engine. If you take your time and are meticulous with your work, pretty soon you’ll be rewarded with a complete ready-to-run engine.

What follows is a look at how to assemble an engine properly in your own home garage using tools and equipment anyone can purchase (or in some cases, rent). Once you complete the process for the first time, you might be surprised at how satisfying it really is. You’ll probably want to follow up with another engine build! Check it out!

A clean working environment
While it’s possible to build an engine almost anywhere, a clean environment is a must. In our garage, we stop any car maintenance activities that create dust and grit. For example, if another project requires grinding then we either move the operation to another spot or figure out another time to get it done. 

You’ll also need a workbench. We have one in our garage, and we’d be the first to tell you it’s too small and regularly cluttered. If your workbench is cluttered, clean it off. If you don’t have a good workbench, a sturdy folding table will do. Once the clutter is reduced, cover the bench surface with paper. Some folks use newspaper. Others prefer butcher paper. We use white poster board because it’s easy to spot little parts, and it’s a bit more immune to oil spills than newsprint.

When it comes to using tools, we always clean them after use. We’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. We’re 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 the pieces? It’s actually rather simple. Scrub everything with hot water and liquid dish soap or car wash detergent. The catch here is that you have to access all of the oil gallery holes, which means the block gallery plugs should all be removed (as is regularly the case with blocks that have been through a machining process). The folks from B&B Performance have a special nine-piece brush kit designed to work in all engine oil galleries (see the tools and source list below). They even include two extra-long brushes for scrubbing oil galleries adjacent to the cylinder block lifter bores.

Our backcountry garage isn’t blessed with a paved driveway or even a cement apron in front of the overhead doors. It’s simply gravel. To circumvent grit accumulation during the wash cycle, we 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, make a 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.

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

We’re fortunate to 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 let the compressor rip. What you really need to do is 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.

After drying
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, 10W-30) or automatic transmission fluid works. So does a light mist of spray lubricant, followed by a wipe down with a clean shop towel. Spray lubricants will naturally displace water so it works in your favor. We 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. We prefer the mechanic-style blue jobs since they don’t tear or shed as easily as kitchen towels.

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

Once the block is spic and span, it should be wrapped up. While jumbo garbage bags work, they’re usually flimsy. We prefer to use an engine storage bag. B&B Performance offers 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. We always wrap the block or engine immediately after work on it has ended. Remember, the main idea is to keep contamination to a minimum.

Plugging the holes
All engine blocks are equipped with a series of pipe plugs. They’ve most likely been removed during the machining and hot tanking process, and obviously should not be present during your cleanup. You’ll need to replace them during engine block preparation. Your local auto parts store, car dealer or machine shop can help you with the respective plugs you’ll need. For a cleaner look, we prefer AN (aluminum) plugs with internal hexes, but brass plugs will work, too. For some applications, a rear cam plug will have to be installed as well. Most of these are of the drive-in (with a hammer) variety. It’s best to leave the cam plug out until later (after the camshaft has been installed). In addition, some engine stand configurations don’t allow access to the back of the block, so you won’t be able to install the plug until the engine is off the stand. 

Typically, the rest of the plugs are equipped with pipe threads. That means the plug is tapered. To seal a pipe thread you can either use Teflon® tape (a pain) or pipe thread sealant. We prefer the latter. Cover the threads with sealant and install the plugs. It’s that simple.

The last thing you need to install is the oil filter bypass valve along with the oil filter adapter. There are plenty of different formats out there, but in our sample engine, the bypass valve simply drops into the block. It’s driven home and set with a hammer and a small socket. The oil filter adapter is a double-threaded affair. The block side should have the threads lightly covered in blue medium-strength thread-locking fluid (don’t use red, as it will require considerable heat if the adapter requires removal). Torque to specs and you are done.

In the next segment, we’ll show how to install the crankshaft and measure the main journal, rod journal and crankshaft thrust dimensions. While these steps are absolutely critical in the engine assembly process, it’s not as intimidating as it sounds. In the meantime, check out these photos.

Tools used:

  • Engine-cleaning brush kit
  • Engine storage bag
  • Thread sealant
  • Medium-strength thread-locking fluid
  • 3/16-inch, 1/4-inch, 5/16-inch and 3/8-inch hex drives
  • 3/8-inch drive ratchet
  • Air compressor
  • Blow gun (air)
  • Pressure washer


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Before a freshly machined engine can be assembled, it has to be cleaned. And really cleaned! You’ll need a bucket or two of hot soapy water, a pressure washer and a set of good quality engine brushes.


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Scrub all of the accessible surfaces with soap and water. Liquid dish detergent works perfectly. So does automotive car wash soap. You’ll have to 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.


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Once the outside is initially cleaned, you can scrub the internal oil passages. The extra-long brushes from B&B Performance 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.


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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. We typically wipe dry multiple times.


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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 we prefer these blue mechanic towels.


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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 – you really can’t get these pieces clean enough.


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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. We’re using the B&B Performance brushes to reach inside the passages.


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Most engines mandate some form of oil filter bypass valve. Our example uses a valve like this.


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The valve slips into the machined passage on the oil filter pad as shown in the first photo. Using an old socket that fits the OD of the valve, seat it with a small hammer. A light tap should get the job done. It has to fit flush with the machined oil filter boss.


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Here’s a look at the oil filter adapter used in our build (most are similar). The side with the internal wrench hex faces outward.


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The oil filter adapter must be locked in place. In this case, Permatex medium-strength thread-locking compound is used. The adapter is tightened with a large hex Allen key.


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Most cylinder blocks have a variety of pipe thread plugs. It’s common practice to use brass or aluminum or even steel plugs (we use Aeroquip aluminum internal hex jobs). No matter what type of plug you use, you’ll need some form of sealant, simply because pipe threads leak without it. You can use pipe sealant tape, but a good thread sealant is easier to use. Coat the thread and tighten the plug. Once the plug is installed, wipe off the excess.


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



Read the next article in this engine assembly series and find out how to install the main bearings and crankshaft, how to check thrust and rod clearances and more.