At this point your Ford Y-block engine should be completely disassembled. If you did it the right way, all of the parts and components are tagged, bagged, and organized. In addition, you should have documented the disassembly process so you can reassemble the engine without great difficulty. The various components of your engine rebuild project now need a thorough inspection and cleaning to reveal any damage, determine which parts need to be replaced, and decide which may be returned to within manufacturer’s specification during the machining process.
This Tech Tip is From the Full Book, 4.6L & 5.4L FORD ENGINES: HOW TO REBUILD. For a comprehensive guide on this entire subject you can visit this link:
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For the disassembly phase, the engine can be separated into four major component groups:
Carburetor, intake manifold,and cylinder heads
pushrods, and rocker arm assemblies)
Rotating assembly (crankshaft, connecting rods, pistons, dampener, and flywheel)
Although the average backyard mechanic is fully capable of visually inspecting and cleaning the rocker arm assemblies, pushrods, and camshaft, I recommend you place the other major engine components into the hands of a professional who is better equipped for it. A professional shop achieves professional results, in part, by being better equipped. After all, you want your engine to be as clean as possible. You don’t want contaminants or debris to ruin an otherwise professional-caliber rebuild job. In my opinion, you cannot achieve the same results with a rented power washer or steam cleaner as a machine shop that is equipped with a baking oven and hot tank.
Media blasting is an effective means of cleaning engine components other than the cylinder block. A session in the blasting cabinet usually removes almost all traces of rust,
corrosion, and old paint from your parts. However, the media used to blast the parts consists of aluminum oxide, or glass beads, propelled by high-pressure air, so parts that have been media blasted require additional cleaning with a liquid solvent to remove any residual media residue that may have collected in out of-the-way places.
(Failure to give your media-blasted parts a secondary cleaning could result in media particles being introduced into your newly rebuilt engine. The results are catastrophic.)
I use a two-pronged approach to inspecting components to identify flaws and determine if they remain within manufacturer’s specifications. First I clean and visually inspect all components (the accuracy of the Mark I eyeball is not to be underestimated). If they pass this test, then I entrust them to an experienced machinist who possesses the proper equipment, such as micrometers, dial indicators, a dial bore gauge, and Magnafluxing capability.
Rocker Arm Assemblies
As mentioned earlier, the Y-block Ford V-8 suffered from oiling woes that were not entirely the fault of the engine’s design. One of the areas affected first by sludgeblocked oil galleries was the rocker arm assembly. Sludge and lack of proper lubrication wreaks havoc on internal engine parts so don’t be surprised if at the very least your rocker arm shafts need replacing during the rebuild.
The good news is that rocker shafts and rocker arms are still available through various parts sources. But this is not so for the stands that support the rocker assemblies, unless you wish to purchase aftermarket high-performance units. Be careful in handling the supports, and make sure they are adequately cleaned before reassembling your rocker arm assemblies.
Rocker Arm Assembly Installation
Step 1: Inspect for Sludge
The rocker arm assemblies have been removed from the engine. Years worth of sludge buildup has likely been caused by paraffin-based motor oils and/or lack of regular maintenance. This amount of buildup should be a red flag and an obvious indicator of neglect. Sludge typically prevents proper lubrication and the resulting wear on parts. On a brighter note, if your rocker arms check out okay (no excessive wear or damage), they are fine to use. Longtime Y-block racer Jerry Christenson praises the strength and durability of the OEM rocker arms even under the most extreme use, such as drag racing.
Step 2: Inspect and Clean Rocker Arm Assembly
After removing the cotter pin from one end of the rocker arm shaft, begin disassembly. A soft-headed or plastic mallet is often required to help separate the stands from the shafts. (Keep components in order as they are removed. Do not reuse cotter pins.) This is another good place to take a photo or two for reference before reassembling these components. This rocker arm assembly is now completely disassembled and ready for inspection and cleaning to determine if it can be reused. The rocker arm assemblies are a critical engine part, and any evidence of wear or damage in this area should result in the replacement of the part. I have seen people use abrasives, such as emery cloth, to smooth scored rocker arm shafts and then reuse the shafts in a rebuilt engine. Keep in mind that your rocker arm shafts have a hardened surface, and once this surface has been compromised, it continues to wear at an accelerated rate, whether or not it has been smoothed.
Step 3: Inspect Rocker Arm Shaft
Visual inspection of this rocker arm shaft reveals baked-on sludge in an area not contacted by the rocker arms. Although this looks bad, it should clean up sufficiently to allow the shaft to be reused.
A combination of dirt and inadequate oil supply has caused obvious galling on this rocker arm shaft, and now it is reduced to the status of scrap metal. Rocker arms and shafts are available for the Y-block V-8 through aftermarket sources such as Sealed Power.
Step 4: Inspect Rocker Arm Tip (Critical Inspection)
Carefully examine the tip of each rocker arm where it contacts the valvestem for signs of wear. The surface face of the rocker tip should be flat and smooth, and there should be no signs of pitting or cupping, which are signs of excessive wear. If only slightly worn, the rocker arm tip may be refaced using a grinding stone, allowing the rocker arm to be reused. Also critical is the inside radius of the rocker arm where it rides on the shaft. The inside radius is examined visually and tactilely. If there’s any wear here, the rocker arm should be replaced. Do not take shortcuts with critical valvetrain components as they have a direct impact on how your engine runs and how long it lasts.
Camshaft and Lifters
If you have any intention of reusing the cam and lifters you remove from the engine, the lifters must be kept in the order they were removed from the block, so that when reinstalled they ride on the same camshaft lobe. Another important point is never install used lifters with a new camshaft. This is a recipe for disaster. When visually examining the camshaft and lifters, the most obvious signs of a problem are a pitting or wear pattern. Also look for any camshaft lobes that appear rounder than others (indicative of a wiped cam) or cupping in the face of the lifters.
With the advances in camshaft design made over the past five decades, it makes perfect sense to retire that old cam and lifters for a less worn and more efficient design. If you are rebuilding a high-mileage engine, give plenty of consideration to replacing the camshaft and lifters.
With the cylinder heads off the engine, it’s time to clean, inspect, and refurbish them. Begin by checking the overall condition of the heads using several simple, unsophisticated, but effective tests. The only tools required to perform this initial assessment of the cylinder heads are a valvespring compressor, a straightedge, some feeler gauges, your hands, and your eyes.
Cylinder Head Inspection and Disassembly
Step 1: Inspect Heads
With the cylinder heads off the engine, examine the combustion side of each head. As expected, the passage that feeds oil from the cylinder block to the rocker arm assemblies is thoroughly blocked with sludge. Thanks to modern lubricants, this common problem in the Y-block Ford V-8 of the 1950s and early 1960s is no longer a concern.
Step 2: Inspect Heads (continued)
Conduct a visual inspection of the gasket surface, combustion chambers, and valves on any set of cylinder heads. In this case, my heads and parts reveal no obvious problems. A simple tactile test, in which you run your fingertips over the surface of the valves in each chamber, helps to determine if any of the valves have sunk in their seats because of excessive wear. The face of the valves, as they appear in each of the combustion chambers, speaks volumes. The exhaust valves typically bear the brunt of the wear and tear in an engine, and therefore, damage often reveals itself here first. The valves should be flush with the combustion chamber. If not, chances are they have sunk due to wear on the seats.
Step 3: Inspect Heads (continued)
Apart from being very dirty, these cylinder heads appear to be in pretty good shape. This set has no obvious discoloration from burning on the heads of the valves or pits in the combustion chambers. Once disassembled and cleaned, further determination of their overall condition can be made. When dealing with five-decades-old high-mileage engine parts, it may be prudent to attempt to find suitable replacements before breaking your rebuild budget with costly repairs. In other words, take your time, do your homework, and be prepared.
Step 4: Inspect Valvestem Tips
A visual inspection of the valvestem tips reveals signs of damage or wear. The tips of the valves may show galling or mushrooming if badly worn. A micrometer will later be used to determine if the valvestems have worn excessively. If this is the case, the valve should be replaced as with any damaged or worn critical engine component. Again, you are dealing with engine parts that are decades old and have gone through thousands of operating cycles. Here, I replaced the valves with Sealed Power units.
Step 5: Disassemble Heads
Here, a pneumatic valvespring compressor is being used in the disassembly of the cylinder heads. Most home shops don’t have the luxury of air tools like this one, but apart from slowing the process, a mechanical compressor works equally well. Over the years, I have seen many poor procedural techniques in engine building. Some mechanics have placed a large socket over the valvespring retainer and struck it with a hammer to disassemble a cylinder head. Never do this because costly damage may result. You could crack the head and/or damage the rockers. Always use the correct tool for the job at hand. Once pressure is applied to the valvespring compressor, the tip of the valve is exposed above the valvespring retainer. Remove and set aside the two split locks that fit into a groove near the tip of the valvestem to hold the retainer and spring in place. When you release pressure on the compressor tool, the valvespring and retainer can be removed from the top and the valve pushed down through the guide and out of the combustion chamber.
Step 6: Check Valveguide Wear
To check the valve, machinist Gil Jordan performs what he refers to as “the wobble test.” He pushes the valve off its seat slightly, grasps the head of the valve firmly, and attempts to move it side to side. Obvious movement indicates guide wear that must be addressed. If the guides pass the wobble test, the machining process progresses.
Valves, Valveseats and Combustion Chamber Inspection
Step 1: Inspect Valvestem
Conduct a visual inspection of each valvestem, and look for signs of galling or excessive wear. Shiny areas are indicative of wear and need to be checked further. Each valve should be examined thoroughly.
Step 2: Measure Valvestem Wear
Use a micrometer to measure several areas of the valve-stem to accurately determine the amount of wear on each. Several checks should be made to each valve to determine if it may be reused. The area closest to the tip of the valve is normally the least worn; evidence of wear increases closer to the head of the valve. Compare the measurements to determine the amount of wear on the stem.
Step 3: Inspect Valveseats
With the valves removed from the cylinder head, examining the valveseats in the combustion chamber reveals rust. The moisture that caused the rust came from a leaking head gasket or an external source while the engine was sitting. However, there are no cracks, pitting, or immediate signs of damage or excessive wear. A valveseat that is obviously no longer concentric is also an indicator of significant wear.
Step 4: Examine Cylinder Heads for Flatness
Use a simple straightedge and some feeler gauges to determine the condition or flatness of the cylinder heads. Although cast-iron cylinder heads typically do not warp as frequently as aluminum heads, it can happen, particularly with cases in which the engine has been overheated. Even if your feeler-gauge check reveals some irregularities in the surface of the head, a cleanup cut of a few thousandths at the machine shop often corrects the situation.
Cylinder Head Cleaning
With the initial inspection of the cylinder heads complete, you need to clean them in preparation for more thorough checks that are performed before machining and reassembly.
Step 1: Check Head Passages for Sludge
An accumulation of rust and scale has clogged the water passages in this cylinder head. This is common in older engines, particularly the Y-block Ford series. Failure to deal with this during the rebuild process may later cause overheating and premature engine failure. The cylinder heads go through cycles in a Bayco oven and hightemperature parts washer to remove this engine-killing buildup. Using modern coolants and proper maintenance keeps your rebuilt Y-block V-8 running cool for many years to come.
Step 2: Remove Freeze Plugs
You can use a head bolt from a small-block Chevy engine to drive the freeze plugs out of a Y-block head. Strike the freeze plug off-center to cause it to rotate in its bore, and then pull it out using a set of pliers. Discard old freeze plugs and never reuse them.
Step 3: Clean and Examine Cylinder Heads
After a cycle in the parts washer, dry the cylinder heads with compressed air and treat them to a thorough sandblasting. Carefully examine each cylinder head casting. Damage, excessive wear, and potential problem areas are much easier to identify now that the castings are clean and free of buildup.
To begin an inspection of a block, check each cylinder bore visually and then with a dial bore gauge. You are looking for obvious signs of wear, tapering of the cylinder bores, scuffing, etc.
Before sending the block to the Bayco oven for the first step in the cleaning process, remove all freeze plugs, cam bearings, dowel pins, and galley plugs. Be sure to make note of the location from which each galley plug is removed, and store the plugs in a secure location because they will be reused.
Step 1: Remove Freeze Plugs
Before the block is cleaned remove all freeze plugs. Use a discarded head bolt or a blunt-ended punch and hammer and strike it off-center to dislodge the plug. Hitting the plug straight-on may cause it to fall into the water jacket and become lodged, adding unnecessary time to the job.
Step 2: Remove Freeze Plugs (continued)
Once the freeze plug has been rotated sideways, use ViseGrips to complete its removal. Freeze plugs should never be reused (discard them).
Step 3: Inspect Water Jackets
Once the freeze plugs have been removed from the water jackets you see years of accumulated rust and scale. This is a common problem in older cylinder blocks. Baking the block in a specialized oven is the most effective way to remove this buildup. This reduces the material to ash; the follow-up is a trip through the high-pressure parts washer.
Step 4: Remove Oil Filter Adapter
Use an impact wrench to remove the threaded oil filter adapter. It allows removal of the plate, which is a major source of sludge accumulation in the Y-block family of engines. If you don’t have an impact wrench, use a 1/2-inch-drive breaker bar and extension, along with the appropriate socket. Some muscle power is required to break the bolt loose.
Step 5: Loosen Mounting Plate
Once the threaded adapter has been removed, use a hammer and brass punch to gently tap the oil filter mounting plate loose. Fasteners do not hold the plate to the block, but sludge likely has it stuck to the block. Caution: Do not use too much force. If the plate is bent during removal, it will leak when reassembled.
Step 6: Remove Mounting Plate
Sludge has accumulated behind the oil filter adapter plate. Remove the plate before cleaning the cylinder block on your freshly rebuilt engine. It is critical to clean this area completely and properly. Sludge buildup here is a common condition in the Y-block V-8.
Step 7: Remove Galley Plugs
Also remove all the threaded galley plugs from the block before cleaning. Apply a penetrating product, such as PB Blaster, and strike the plugs with a hammer and brass punch before attempting to loosen them.
Step 8: Remove Galley Plugs (continued) (Professional Mechanic Tip)
Use a torch to apply heat if the hammer and punch method fails to loosen the plug. A combination of heat and then a sharp blow with a hammer and punch may do the trick. Be careful whenever you work with an open flame.
Step 9: Remove Block Plugs
Use an Allen or hex-head socket, extension, and breaker bar or ratchet to remove threaded plugs from the block. The old-fashioned Allen/hex key does not provide adequate torque to get the job done, and you may end up with a rounded-off plug that must be drilled out.
If you’ve heated the plug and worked at it with a hammer and punch but it still won’t come out, you may have to drill it out. Caution: Do not give up and leave the plug in place because dirt may remain behind and that could cause damage to your newly rebuilt engine. When drilling out the plug, be sure to take your time and use a drill bit that is smaller in diameter than the plug so you do not damage the threads.
Step 10: Remove Cam Bearings (Special Tool)
Use this specialized cam bearing removal tool to extract cam bearings from the block before cleaning. Cam bearings should not be left in the block during the cleaning process and never reuse them.
Slide the tool into the cam tunnel and expand it to fit the inside diameter of the bearing by turning in a clockwise direction. When the tool has been expanded and is firmly seated against the bearing, strike the end of the bearing tool to drive the bearing out of the journal.
Step 11: Remove Cam Bearings (continued) (Special Tool)
Once a cam bearing has been removed from its bore, the tool and the bearing slips off the fixture. Repeat this process until all the cam bearings have been removed.
Step 12: Place Block and Heads in Bayco Oven
The disassembled cylinder heads join the block for an overnight 750-degree bake in the Bayco oven. This is the first step to looking like new for these parts.
An overnight stay in the Bayco oven has converted the five decades of grease and grime into ash.
Next up is the Magnaflux process, which reveals any cracks not visible to the naked eye. Satisfied that the block is sound, you need to remove any rust and scale that may have been left during the previous steps.
Deck Area Inspection
The deck surface of the cylinder block is first examined visually and tactilely; you’re looking for signs that you can see or feel with your hand such as pitting, gouging, or cracking. This is followed by a simple, but effective, means of determining warping by using a straightedge and feeler gauge applied across the surface from different angles. Finally, the deck surface is Magnafluxed to reveal any crack that cannot be seen with the naked eye.
Step 1: Inspect for Block Cracks (Critical Inspection)
The cylinder block deck surface is another area that’s prone to cracks. The bolt holes closest to the perimeter of the block and nearest the water jackets are particularly prone to cracking. Typically, you see spider-web cracks emanating outward from the bolt holes. Although cracks are not good news, cracks may not reduce the status of your cylinder block to scrap iron. The location and size of the crack and cost of repair are the determining factors as to whether a repair can, or should, be attempted.
If a crack is present, the magnetic material used in the Magnaflux test accumulates and adheres to the cracked area so you can easily see the crack
Step 2: Check for Casting Flash
This block has received a thorough baking and washing to remove the accumulated grease, rust, and scale, but casting flash still remains at the opening to a water jacket in the front of the block. This flashing, a thin layer of metal left over from the foundry’s casting of the block, can cause stress risers, and cracks in the block may develop. It also impedes coolant flow and could cause your rebuilt engine to run hot.
Step 3: Remove Casting Flash (Professional Mechanic Tip)
Use a die grinder to remove the casting flash from the water jacket. Removal of this material allows for maximum coolant flow within the block and ensures proper operating temperatures in the engine. Remove only the flashing material from water jackets. Do not attempt to increase the size of any openings.
Step 4: Remove Casting Flash (continued)
After several minutes of grinding, the water jacket opening is now the proper diameter and without any obstructions. Grind down the parting line. By doing this you have helped eliminate the potential for overheating your newly rebuilt engine. Use a bimetal grinding bit, suitable for use on cast iron, on the rotary tool to remove flashing material.
Step 5: Inspect Water Jackets
The water jackets surrounding the cylinders are a critical area for cooling the engine. Even after a thorough cleaning, some leftover rust and scale may remain. Carefully inspect these areas and use an inspection light if necessary to make sure all rust and scale have been removed from the water jackets.
Step 6: Remove Water Jacket Rust and Scale
You can feed a coat hanger or a welding rod into the water passages to remove leftover rust from the water jackets in the cylinder block. Every piece of unwanted rust removed from the cylinder block improves cooling and increases engine longevity.
Just a short time scraping loose metal from the water jackets of the cleaned block resulted in this pile of rust. Allowing rust to remain in the block adversely affects the engine’s cooling and creates hot spots that decrease combustion efficiency
Main Bearing Saddle Inspection
Verify the alignment of the main bearing saddles and caps in relation to factory specification and one another. Any discrepancies noted here are corrected by line honing the block during the machining process.
You can lightly use a Mill Bastard file to remove sharp edges from the main bearing saddles in the block in preparation for checking the line bore to verify that the main bearing bores are within specification. The main bearing caps receive this treatment also. You must remove sharp edges or burrs to ease bearing installation during reassembly.
The gasket mounting surfaces of the block are dressed with a sander using fine-grit paper, which smooths but does not gouge. The purpose here is not to remove a lot of material but merely smooth out any rough spots or burrs and help prevent future leaks when the engine is reassembled. You may also find that even after a thorough cleaning, stubborn gasket material remains on some surfaces.
Make sure the threads of the main bearing bolts are clean and not damaged. Examine the spiral pattern of the threads, and if it is wavy or malformed, throw away the bolts. The 312 blocks are prone to cracks in this area because of their enlarged main bearing saddles and inaccurate torque specifications initially listed by the factory.
Step 1: Apply Motor Oil
Apply a light coating of 30-weight motor oil to the threads on each of the main bearing cap bolts before assembly. This ensures a proper torque reading when the bolts are tightened. Coat the underside of the head on each main bearing cap bolt with oil. Failure to do so could result in a false torque reading. I prefer to use a squirt can to do this, but you can brush it on or work the oil into the surface with your fingers.
Step 2: Snug Main Bearing Cap Bolts
Use a speed wrench to snug up the main bolts. This method allows you to feel for any problems in the threads, such as burrs. Do the same when you’re assembling the engine. As you tighten the main bolts, feel for any binding or excessive resistance. If you feel some, chase the threads again to make sure they are clean. If that doesn’t resolve the problem, tap the bolt hole, but that should only be required in severe circumstances. Remember, air tools should never be used for this process or other delicate assembly processes.
Step 3: Tighten Main Bearing Cap Bolts (Torque Fasteners)
Tighten the main bearing cap bolts in three increments and alternate from side to side until you reach 95 ft-lbs. The correct torque spec for OEM hardware is 95 ft-lbs, but torque specs vary between aftermarket and OEM hardware. In addition, the assembly oil or lube also affects the final torque spec. Follow the hardware manufacturer’s torque spec and assembly lube recommendations and correctly follow the torquing process. If you arrive at the wrong spec, you could break bolts or engine failure could result at start-up. For these bolts, first torque to 32, then 64, and finally 95 ft-lbs. Be warned that incorrect torque values for Y-block main bearing bolts have previously been published. Overtightening of these bolts could result in cracks developing in the block’s main bearing webs. If you use aftermarket hardware and/or assembly paste (such as ARP provides) be sure to follow the bolt manufacturer’s torque recommendations.
Step 4: Measure Bores (Critical Inspection)
With the main bearing caps torqued into place, use a dial bore gauge to measure each main bearing bore. You must ensure that the main bearing bores are concentric and in alignment to one another; this is critical to engine longevity.
Pistons and Connecting Rods
Consider the number of rotations as well as heating and cooling cycles experienced by these critical parts before an engine rebuild is necessary. A visual inspection of the pistons can provide a wealth of information about the condition of the engine. Beginning with the combustion surface (top) of the piston, evidence of excessive carbon buildup reveals the use of poor-grade fuels or an improperly tuned engine. Pitting or burning on the surface of the piston indicates a lean condition in the cylinder, and wet, oily deposits are indicative of valveguide or piston ring wear. Scuffing (shiny areas) on the skirts of the pistons also indicates excessive wear. At the machine shop a micrometer is used to accurately determine the amount of wear by measuring several areas of each piston skirt.
In order to remove the pistons from the connecting rods, you can use a pair of snap ring pliers to remove the wrist pin retainer from one side. Since Y-block engines have full-floating wrist pins, the pin can be easily tapped out, disconnecting the piston from the rod. The wrist pin retainer has a small hole in the end of each of its loops. Insert the tip of the snap ring plier into these holes, so you can compress the retainer enough to allow removal from the groove in the piston.
Place the connecting rod securely in a soft-jawed vise, and use a brass mallet to tap out the connecting rod bolts. Knurl the connecting rod bolts where they fit into the rod to keep them from spinning.
Connecting rods should be reconditioned for almost all rebuilds. The bearing ends that ride on the crankshaft are resized (brought back to a concentric shape within recommended specification by machining) and the piston pin bushings in the small ends are replaced. I make it a habit to replace the connecting rod bolts and nuts with new hardware.
Crankshaft and Vibration Dampener
The first step to identify excessive wear or damage to the crankshaft is reading connecting rod and main bearing inserts. Bearing surfaces that are worn through to the copper coating are an indication of wear. Excessively worn bearings show signs of thinning in portions of their material; this is a result of severe pounding caused by a combination of wear and/ or lack of proper lubrication. When reading a connecting rod bearing insert be aware that the top portion of the insert bears most of the load in an engine and shows the most wear.
Problems with the crankshaft that can be detected upon initial inspection are in the area of the snout and keyway, where the vibration dampener mounts, and, of course, the machined areas of the main and rod journals.Running a fingernail across the polished surfaces of the crank journals may reveal small grooves caused by wear. Even if no obvious signs of wear are present the crankshaft journals should be checked with a micrometer to determine if they remain within factory specifications or have been previously machined. After a thorough cleaning, the crankshaft should be Magnafluxed to reveal any hidden cracks.
The vibration dampener is often overlooked during an engine rebuild, and failure to identify problems with this critical component in the rotating assembly may lead to later problems. In conducting a visual inspection of the vibration dampener, look for obvious signs of wear, such as cracking or separation in the rubber between the inner and outer portions of the dampener. You also need to check the machined inner and outer surface of the dampener and its keyway(where it mounts on the snout of the crankshaft and contacts the timing cover seal).
Crankshaft and Vibration Dampener Inspection
Step 1: Inspect Machined Areas
Visually inspect the machined areas of the throws where the connecting rod and main bearings ride. If they can be felt, they can be seen. Initially look for obvious cracks, grooves, burrs, or evidence of heat (a bluing of the metal on the journal). Inspect the main bearings to see if any signs that the crank might be bent. If the crank is bent, you see an uneven wear pattern on the bearing surfaces. Typically, a qualified machinist performs the run-out procedure. In this case the machinist, taking all the above factors into consideration, chose not to go to the additional expense. You can check run-out by installing the main bearings in the block, lubricating them with oil, setting the crank in the block, and then install the number-1 and number-5 main caps. Set up a dial indicator with magnetic base to contact the number-3 (thrust) journal of the crankshaft. Slowly turn the crank and note any deviation.
Step 2: Check Specs (Documentation Required)
Use a micrometer to determine if the crankshaft is still within factory spec and if its journals have been previously machined undersize. Check each journal in turn, and record the results. Rod journal specifications for both the 292 and 312 should be 2.1880 to 2.1888 inches. The 292 main bearing journals should measure 2.4980 to 2.4988 inches. The 312’s larger main bearing journal specifications are 2.6235 to 2.6243 inches.
Step 3: Test for Cracks
The crankshaft is also treated to a Magnaflux test for cracks as was done with the cylinder heads and block. A magnetic powder is applied to areas of the crankshaft prone to cracks, such as oil supply holes, after which a magnetic field is introduced. The magnetic powder collects in any cracks. For the most part, a crack in a crankshaft may not spell doom. In the case of a crankshaft, the location, length, and depth of the crack are the determining factors. I have seen crankshafts used in racing engines that have detectable cracks.
Step 4: Chamfer Oil Holes
This particular crankshaft passed all tests with flying colors. It is not cracked, and the journals are within factory spec and need only a polishing of the rod and main bearing journal surfaces to be serviceable. The next step in the process of preparing the crankshaft is to carefully use a die grinder to chamfer the oil holes in the journals to improve lubrication. Chamfering refers to using a die grinder with a polishing stone to remove the sharp edges from openings. Doing so allows oil to flow more smoothly. After this, the crankshaft will receive the first of several cleanings in preparation for polishing. Measuring crankshaft runout is typically a machine shop procedure. The at-home mechanic can check runout by installing the main bearings in the block, lubricating them with oil, setting the crank in the block, then installing the number-1 and number-5 main caps. A dial indicator with magnetic base is then setup to contact the number-3 thrust journal of the crankshaft. The crank is then slowly turned and any deflection is measured.
Step 5: Polish Crankshaft
With the crankshaft cleaned and the oil holes chamfered, it is now ready for polishing, which is followed by a final cleaning with solvent. The crankshaft and most other critical engine components have been cleaned several times before assembly of the engine begins. Critical engine components cannot be too clean.
Polishing the crankshaft journals involves the crankshaft being set up in a lathe that spins at low speed during the polishing process.
Step 6: Polish Crankshaft (continued) (Important!)
Mount the crankshaft in the lathe for crankshaft polishing. Use two different grit-polishing belts to smooth the surface of the journals. One important note: During this process the crankshaft must be spun in the same direction in which it rotates in the engine. This is because of the microscopic peaks in the metal created during the machining process.
Step 7: Remove Sharp Edges
After inspecting the crankshaft to identify any sharp edges or other stress risers, use a die grinder to remove them. Sharp edges can produce stress risers, and this can lead to outright failure of the crankshaft, so you need to identify these areas and grind them down. Using a die grinder and bit suitable for cast iron, carefully grind down these edges to prevent cracks from forming. The crankshaft receives yet another thorough cleaning before the engine assembly begins.
Step 8: Verify Crankshaft Type
It is easy to differentiate between the 292 and 312 crankshafts and determine which crankshaft you have. The 312 crankshaft (right) has a button (raised round area) on the flywheel flange while the 292 crankshaft (left) does not. The stroke and main journal diameters are also different between the 292 and 312 engines.
Step 9: Check Crankshaft Balance
This is a crankshaft that has been dynamically balanced. During this process, Mallory metal was added to the crankshaft until proper balance was achieved. If you change components of the rotating assembly during your rebuild, check the balance to avoid the possibility of internal vibration, which can cause catastrophic damage to the engine.
Step 10: Verify Fit
This 312 Y-block crankshaft main bearing journals have been machined to a 2.498-inch diameter so the crank fits in a 292 block. The oil slinger at the rear of the crank is also turned down because most machine shops do not have a stone narrow enough to perform the task of machining this area separately. There are two schools of thought on this particular procedure. Some say that when using a neoprene rear main seal, which the 292 has, it causes no problems. Others say that turning down the slinger creates oil leaks.
Step 11: Inspect Oil Slinger
This is a Y-block crankshaft with the oil slinger intact as delivered from the factory. The purpose of the slinger is to divert engine oil away from the rear main seal area and prevent leaks. This engineering feature was particularly critical in engines that used a rope-type rear main seal.
Step 12: Inspect Dampener(Professional Mechanic Tip)
More than 50 years have taken their toll on this dampener, and, as a result, the rubber ring between the inner and outer portions of the dampener is cracked. A crankshaft dampener has a reliable service life, and after 50 years, it’s a good idea to replace the dampener. These cracks are a red flag, so this dampener should be replaced to avoid future catastrophic failure on any newly rebuilt engine.
Careful examination of this dampener reveals that the rubber insulator ring and the machined surfaces are sound. The timing marks are in excellent condition as well, so you are able to easily set timing using this dampener. This dampener is serviceable and will be used on the rebuilt engine.
Written by Charles Morris and Posted with Permission of CarTechBooks