OK, so you have all of your parts in hand, whether brand-new or freshly machined. We’re definitely making progress toward enjoying a fresh Gen III/IV engine—but let’s fast forward a moment. Say you’ve got your rebuilt engine up and running, and everything is going great. You’re enjoying the new-found power of your LS-equipped ride, and wake up every morning anxious to drive it (or race it, as the case may be). Now imagine that you check the dipstick and discover you’re a little low on engine oil. But instead of adding some fresh oil from a sealed container, you instead grab a handful of dirt and throw it down the fill cap. Such an act may sound far-fetched, but in effect, this is exactly what you’d be doing if you didn’t take the time to properly clean all engine components prior to assembly!
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There are a few reasons why this analogy holds. First and foremost, although most machine shops do a very meticulous job of cleaning all of your freshly machined components before you pick them up, there’s always the chance that something has slipped the trained eye (and parts washing equipment) of the technician. At best, leftover metal shavings will be small and cause scoring on parts of the engine, reducing their useful life. At worst, a large enough chunk of material left inside the engine block can easily clog your main oil gallery, robbing the engine of oil pressure and destroying it within a matter of seconds. Ultimately, you are the one responsible for ensuring all engine components are 100 percent clean before assembly.
Moreover, a metal component that appears outwardly clean and shiny may hide a dirty little secret—literally. Bits of dirt and metal are often too small to be seen with the naked eye, but no matter how small these particles are, they can still cause damage. Probably the best example of this occurs with cylinder bores. During the honing process, tiny metallic particles become embedded in the cylinder wall, and they can only be fully removed via meticulous scrubbing using the correct chemicals. Your machine shop may have done some of this for you, but don’t assume it was done to its full extent.
Finally, even if you’re using brand-new, out-of-the-box parts that require no machine work (for example, a set of fully-assembled high-performance cylinder heads), there’s no guarantee they are clean, either. Parts may have been sitting on a shelf collecting dust before they were boxed up and sent to you, and the same goes for the box they were shipped in! Think about all possible sources of contamination along the chain of custody of any item, and you’ll quickly realize that when it comes to engine components, virtually nothing is truly “ready to install.”
A little bit of effort and elbow grease during the cleaning process will pay huge dividends in LS engine longevity, not to mention efficiency and horsepower. As time consuming as this process may be, it is not to be taken lightly!
The good news about engine component cleaning is that few specialized supplies are needed to perform the process properly. In fact, you probably have most of the items you’ll need to clean your engine parts, and a lot of the rest are readily available in your local hardware store. Beyond these run-of-the-mill supplies, the few more specialized items are readily available from engine builder suppliers like Goodson. We’ll show you everything you need here.
You’ll need substantial amounts of a good general cleaning solvent. This will be used both to soak dirty parts as well as to wipe surfaces with. Probably the best such solvent is mineral spirits, an item that is readily available in the paint section of any hardware store. This is the same stuff most machine shops have circulating through their wash tubs. It’s not a bad idea to have some carburetor cleaner (the sensor-safe type) and brake parts cleaner around, either—they’ll do a similar job for surfaces where a spraying action is preferred. The important thing to keep in mind when selecting general cleaning solvents is to find types that will evaporate and leave no residue.
Other cleaning agents
There are a few other liquids you’ll want around to help you in cleaning, some of which aren’t usually thought of as cleaning agents. Many of you probably know that WD-40 is very good at dissolving grease, rubber, and other substances, and it will come in handy for this very reason. Also pick up at least a quart of automatic transmission fluid. This may sound strange to you, but the detergent properties of ATF make its cleaning ability second to none when it comes to removing leftover metallic particles from your cylinder walls. Engine degreaser (the stuff used to spray down and rinse off a dirty engine compartment) can be used to clean heavily soiled intake manifolds and other non-metal items, but must be avoided on internal engine parts.
You will want containers of various sizes in which to soak and wash parts. Either plastic or metal containers will do, but you’ll need to get them nice and clean before use—mom’s old baking trays will work, but they cannot be rusty. Feel free to improvise with items that would otherwise be garbage, such as old candy containers. Any container used should be impervious to solvents, and not returned to kitchen duty when you are through!
There are a few different types of towels that you’ll want to have around to help wipe parts clean. Shop rags are useful for very greasy situations, as well as for hand wiping. For slightly more delicate situations, find a good quality paper towel with a thick weave, and get at least a 12 pack of them, you’ll go through them quickly! Even the best paper towel will leave some lint behind, and because of this, lint-free cloths are recommended for final cleaning operations. These are a little harder to come by (many are advertised as “non-linting” but really aren’t), but are worth having. The best are those known as assembly wipes, and they’re readily available from engine supply outlets.
Engine brush kit
You’ll need more than just an old toothbrush to properly clean your engine parts. Here’s one item you won’t find at your local hardware store: a dedicated engine brush kit, inclusive of a variety of specialized brushes for cleaning everything from cylinder bores to the smallest crankshaft oil passage. A good one will also have one or two small hand-type brushes for surface cleaning as well. Again, Goodson is a good source for one of these.
It is critical that you have a source of compressed air, as this will allow you to blow contamination out of bolt holes, oil passages, and other areas that cannot be physically reached (or often, even seen). If you don’t already have one of these in your garage or shop, small units are inexpensive and will do the job just fine. You’ll want to purchase one that can supply at least 80 psi or so.
Other items you may find helpful during the cleaning process, in no particular order, include: razor blades (to scrape dirty surfaces); a flashlight (to check for dirt in dark passages); general washing brushes; thread cleaning taps (to remove stubborn buildup in threaded holes); metal protectant (a dedicated rust inhibitor, or WD-40 if you don’t have any); as well as storage bags to cover clean parts.
Some of you may have noticed that, with the exception of its use to rinse off engine degreasers, water and water-based solutions are conspicuously absent from the supply list above. Simply put, we don’t recommend washing down any metal parts of an engine with water of any kind. If a component is dirty enough to tempt you to get a hose out, take it back to the machine shop and have it jet washed! The danger, of course, is that water invites corrosion. Though theoretically it is possible to clean parts using water if you immediately dry and spray them with rust inhibitor, the problem is that water may sneak its way into nooks and crannies of a part that you may never see. In this way, it may never evaporate—or may leave damage by the time it does. Keep in mind that even though many parts of Gen III/IV engines are made from aluminum, there still is a lot of iron to rust—especially with an iron block! Again, the only use for water that we condone is with rinse-off-type engine degreaser (such as “Gunk”), which should only be used on plastic parts like intake manifolds that do not touch engine oil. Never use water to clean internal engine parts!
An engine build is wrought with safety hazards, and a lot of them have to do with dropping heavy parts onto your person. But easily the most dangerous steps of any engine rebuild project are during parts cleaning. The chemicals used can harm the skin and eyes, and their fumes can be toxic, or even flammable. Not taking the proper precautions here could be the biggest mistake of your life.
Be sure to read all warning labels to inform yourself of all chemical hazards, as well as any mixing danger of the solvents you are using. Have an open work-space ready with lots of ventilation. Depending on what you’re using to clean, even breathing masks may be a good idea. Latex and/or other types of rubber gloves should be worn at all times, especially when using harsher chemicals. Goggles will be needed to protect your eyes, whether it’s from the occasional chemical splash or while using compressed air. These items won’t get your engine parts any cleaner, but they’re mandatory for your safety!
Because you’ll be up-close-and-personal with your engine parts during component cleaning, it’s a great time to keep one eye open for any problems like damaged new parts, or refurbished parts that have had machine work incorrectly performed. (In-depth pre-assembly procedures using precision tools will be detailed in the next chapter, although the human eye can spot some problems that no tool can measure.) Should you run across any of these issues, don’t lose your cool: remember, the sooner you discover and address them, the better off your rebuild project will be!
Step-By-Step Engine Component Cleaning
Step 1: Ready to Begin Cleaning
Before getting started, make sure that the area you’ll be working in is cleaned up. The floor should be swept and all table surfaces should be wiped down or covered with plastic. With all of your cleaning supplies close at hand, don some old clothes as well as all of your safety equipment. Set aside a large amount of time to do this—you won’t want to take breaks and let contamination set in, or be interrupted and forget what you were doing. You will also want hand cleaning solution nearby to frequently wash up, preventing cross-contamination of parts. This will also help you get any harsh chemicals off of your skin ASAP!
Step 2: Initial Block Inspection
With your block mounted on an engine stand, remove the main caps (if you haven’t done so already). Also remove any and all engine block plugs—oil gallery plugs in particular should not have been left in during machining. Begin inspecting all areas of the block for any and all contamination. Too much debris, and you’ll want to take the block back to the machine shop for a jet wash. Don’t be unreasonable about what you can accomplish here—the removal of a significant amount of dirt or metal shavings requires special equipment you simply do not have.
Step 3: Inspect and Clean Threaded Block Holes (Important!)
Inspect all threaded holes in the block, especially main and head bolt holes. Don’t assume your machine shop took care of this for you, even if you asked them to! Any significant leftover gunk needs to be cleaned out so that bolts (or studs) can thread in properly. Factory head bolts utilize locking compound on their threads, and their holes normally have more than enough left over to create a problem when the time comes for new fastener installation. Chase any such hole with a clean-out tap, being sure to use lubricant on the threads. Threaded holes can also be brushed if the buildup is minor, but this still isn’t as effective as a cleanup tap. If you detect any thread damage anywhere on the block (or on any other engine component for that matter), consult “Fasteners and Threads: Problems and Solutions,” on page 23.
Step 4: Inspect Block Oil Galleries (Critical Inspection)
Using a flashlight, visually inspect and make note of the following oil passages in the block (see “Oil Galleries” on page 83 to help you pick out which is which):
Step 5: Clean Block Oil Galleries
Whether or not you detect visible dirt in any of the oil galleries you’ve just noted, they must all be cleaned. A good engine brush kit has a variety of engine brushes to choose from. Using the appropriate size brush soaked in mineral spirits, scrub each oil gallery we listed in the preceding step. The main oil gallery is one place that a brush with a very long handle will be needed. A twisting motion helps dislodge dirt as you scrub. You should take the brush out and rinse/re-soak in mineral spirits while scrubbing each passage a few times. After doing this, take the brush and wipe it on a paper towel. If you see any dirt come off, you will need to keep scrubbing. Depending on your style of engine stand, you may have to take the block on and off of it to get better access to the rear of the engine during this step.
Step 6: Clean Other Block Passages
Scrub all sixteen lifter bores using the appropriate-size engine brush, as well as all five cam bearing bores. Since you’ve probably already had your machine shop install cam bearings into these bores, either an extremely soft bristle brush must be used, or you can simply use a mineral spirits-soaked towel to wipe them (our preferred method). The latter technique will require reaching between the block bulkheads for the middle bearing bores. Also brush the crank sensor hole on the lower rear passenger side of the block, the cam sensor hole at the top rear of the block (Gen III engines only), the holes for the main cap side bolts, and any other unthreaded hole you see.
Step 7: Blow Out Block Passages (Safety Step)
You should have been wearing them all along, but now is the time to definitely make sure you have safety goggles on. Blow out all passages you have scrubbed with compressed air. Also blow out the block coolant passages, including those leading from the water pump to the block as well as those running between the block and heads. Note that we didn’t scrub any of these coolant passages since they are not as critical (and are probably clean enough from the washing done at the machine shop); you can probably just blow them out and visually inspect to make sure nothing is in there.
Step 8: Clean Cylinder Walls (Important!)
Equally as important to clean as the oil galleries are the cylinder walls. Again, unless your machine shop did a completely superb job here, there will be leftover particles imbedded into the cylinder walls from the honing process. Don’t take the machine shop’s word for it that they’re ready for assembly! If your engine brush kit included a large bore brush, you should soak it in mineral spirits and scrub each bore. Then, move to paper towels and, moving in multiple directions, scrub with mineral spirits. Acrylic lacquer thinner can also be used, but be careful with this stuff. Final bore cleaning should be done using towels (preferably, non-linting) and automatic transmission fluid. Turning the towel often, continue until every inch of each bore has been scrubbed with ATF and no noticeable particulate is seen on the towel. Take note that you must perform this bore cleaning process one more time after ring fitting, so you don’t have to go crazy here if cleaning for pre-assembly.
Step 9: Clean All Other Block Surfaces
Using mineral spirits, wipe every other surface inside the block, as well as all gasket sealing surfaces (for the front and rear covers, etc.); you may use a razor blade to scrape these surfaces (not recommended on deck surfaces), so long as you are careful not to damage the soft metal of aluminum blocks. Watch that your towels do not send lint down any oil passages (or anywhere, for that matter). Here again, you’ll need to turn your towel often, add mineral spirits, and rub until little or no dirt is seen on it.
Step 10: Crankshaft Cleaning
The crankshaft is a somewhat bulky item, so to make things easier and safer, it’s best to mount it on an inspection stand during cleaning. (If you don’t have one of these, you can also bolt a flywheel or flexplate on the back and have the crank standing vertically while you clean.) Clean all journals and other surfaces using non-linting towels with mineral spirits, and similarly brush the small oil passage holes in each journal. Also, on most factory and aftermarket cranks, there is a hollow hole that runs the length of the crankshaft down its centerline; now is a good time to look and make sure its rear plug is in place, or you’re in for a major oil leak. (Consult your machine shop if the plug is not there.)
Step 11: Clean Other Large Internal Engine Parts
Clean all surfaces of the cam, pistons, and connecting rods using clean non-linting towels and mineral spirits. Be mindful of the piston ring grooves. Also, Gen III and IV cams are hollow (some not all the way through), so you should brush the inside of the cam, and in addition, the oil passages in the second cam journal from the front (this last point applies to VVT-equipped engines only). Have a look at the bolt holes in the connecting rods and front of the cam for any contamination as well.
Step 12: Solvent Soak Small Parts
Many smaller internal components—such as pushrods, bearings, and piston rings—can be fully soaked for the ultimate in cleanliness. This also works well with any bolts you may be reusing. Let the parts sit in a bath of clean mineral spirits awhile, then remove and wipe them off. Don’t forget to blow out any internal passages, especially with pushrods. Note: if you choose to clean piston rings this way, do not mix the compression rings up if you’ve already file-fit them and are cleaning for final assembly!
Step 13: Non-Soakable Parts
Solvent soaking lifters and rocker arms is not recommended. You don’t want to pull the oil out of the inside of these items and destroy them at initial startup—their internal needle bearings need the lubrication. An external mineral spirits wipe will suffice. If these items are particularly dirty (for example, if they are being reused, this is strongly discouraged for lifters) and you insist on soaking them, you’ll need to subsequently submerse them in oil for a long period of time and move them under the surface to work the lubrication in. The same thing goes for your timing chain.
Step 14: Cylinder Head Cleaning
If you’re reusing your stock cylinder heads, you should have had your machine shop wash them after performing the required machine work. If they did not do this, take your heads back and have them do it for you before performing your own cleaning. Brand-new cylinder heads require their fair share of cleaning, too. If your heads are not currently assembled, scrub the valve guides and other holes using brushes soaked in mineral spirits. Blow out all pushrod holes, bolt holes, intake/exhaust ports, and other passages in the head using compressed air (safety glasses, folks!). Ensure that the exhaust manifold bolt holes are clear of threadlocking compound (used heads only). Finally, wipe all head surfaces with mineral spirits.
Step 15: Cleaning Engine Covers
Clean the engine covers, including the front cover, rear cover, valley cover/LOMA assembly (as applicable), and oil pan. Pay attention to any residue on the gasket sealing surfaces. Special care must be taken with the oil pan, which will be particularly gummed up. Different pans also have varying baffling setups in them, as well as different fittings and a bypass valve about the oil filter, so be sure to remove any such items (and replace with new items as necessary) during cleaning so you can get into every nook and cranny. Some of these engine covers have sensors like cam position sensors, temperature sensors, or oil level sensors that you’ll want to be careful of, and the LOMA will be particularly delicate, what with electrical connectors and lots of seals and solenoids. Any under-valley-cover baffles (for the PCV system, as with the valley cover shown) should be removed and the inside cleaned, or at a minimum flushed with solvent and blown out. Also note the condition of Oring- style seals on the underside of Gen IV valley covers. Do not expose these to harsh solvents, and replace them if they are not in good condition— these things seal oil galleries! The knock sensor grommets on the underside of Gen III valley covers should be wiped as well (or if in poor condition, removed and replaced).
Step 16: Clean Intake Manifold
Your intake manifold may be dirty on the outside, but this pales in comparison to the state of affairs on the inside, where there will at a minimum be a coating of oil (thanks to your PCV system). The intake is cleaned most easily using a spray-on, rinse-off engine degreaser (water is OK to use here because there is no worry of corrosion with plastic). Before doing this, remove any sensors as well as the eight factory fluorosilicone intake port gaskets (car intakes only; truck intakes use carrier-style gaskets) and throttle body gasket. Use new ones; discard the old ones. Make sure you get all gasket grooves clean, or you risk compromising gasket seal.
Step 17: Clean Throttle Body
Clean your throttle body, which more than likely will have some carbon buildup inside. Carb cleaner works best for this, but make sure it’s the sensor-safe stuff (use so-called “intake/throttle body cleaner” if you’re not sure). Remove all sensors from the throttle body before doing so; it’s a good idea to acquire new ones of these if your engine had a lot of miles on it. Take special care with the electronics on drive-by-wire throttle bodies. Here again for engines that saw a lot of miles, replacing such a throttle body’s motorized actuator may be a good idea (shown intact and removed side-by-side).
Step 18: Clean Other EFI-Related Hardware
For best performance, used fuel injectors should be professionally cleaned and flow-tested, as they can clog over time from impurities in gasoline or E85. If there is an incurable problem with the injectors, they can be replaced. As far as what you can do yourself, you’ll at For best performance, used fuel injectors should be professionally cleaned and flow-tested, as they can clog over time from impurities in gasoline or E85. If there is an incurable problem with the injectors, they can be replaced. As far as what you can do yourself, you’ll at least want to remove and discard the O-rings at the top and bottom of the fuel injector and acquire new ones. Fuel rails should, at a minimum, be sprayed out with sensor- and fuel-injector-safe carb cleaner, with particular attention being paid to injector O-ring seating surfaces for damage.
Step 19: Clean All Other Miscellaneous Parts
Clean all other parts we haven’t mentioned specifically, such as the crankshaft oil deflector, main bearing caps, and oil pump pickup tube (make sure its screen is completely free of debris). On a similar note, you will want to keep certain solvents away from rubber and plastic, so use care when cleaning the “barbell restrictor” and any O-rings. A dry cloth wipe is the best way to clean cam, crank, and other sensors (if they came from an engine with a lot of miles, most of these items should be replaced anyhow for optimum reliability). Items like the cam retainer plate need to be treated with care as well (there is a built-in seal on the back). Inspect all parts before you clean, and definitely before you soak!
Step 20: Prep Items for Temporary Storage (Important!)
It’s best to begin your engine pre-assembly or final assembly as soon as possible after completion of parts cleaning. If the parts will need to be stored for any length of time, however, you will want to take steps to ward off rusting of any iron or steel parts. Cylinder walls and crankshaft journals are particularly susceptible to corrosion, and it’s advisable to spray those items immediately with a protectant like WD-40 or, better yet, a specialized rust inhibitor like this one from Goodson. All parts of an iron block should be cared for as well if it will be sitting awhile (by the way, now is an excellent time to mask off and paint the outside).
Step 21: Store Clean Items
If you’re not pre-assembling or assembling immediately, all cleaned items should be stored in plastic bags or with specialized wrap like this stuff from Goodson. Less critical items like bolts, engine covers, and sensors are OK in a clean cardboard box or sealed plastic container. A large garbage bag works well for larger items like engine blocks. Make sure any solvent has evaporated before sealing anything off. Congratulations! You’ve completed component cleaning and can now move on to pre-assembly (or final assembly, as the case may be).
Written by Chris Werner and Posted with Permission of CarTechBooks