Before you attempt a short-block disassembly, plan ahead. Instead of blindly removing items and scattering them in a pile, reserve a table or workbench to keep all parts organized, even if you plan to replace most or all parts. Also, it’s a good idea to take photos during disassembly. These will serve you well during reassembly, unless you are already very familiar with the specific engine design.
Step by Step
Drain all liquids including, engine oil and coolant, and dispose according to state and local guidelines. With the oil pan, water pump and all driven accessories, intake manifold, and flywheel removed, remove all rocker arms and pushrods. Organize all rocker arms and pushrods for original position so that you can determine the location for any unusual wear.
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Remove all valve lifters. If flat-tappet lifters are used, remove them one at a time. If roller lifters are used, remove them one pair at a time if they are connected with a tie bar; remove them individually if their orientation is guided by “dogbone” guides. If you’re dealing with an LS engine, a plastic lifter “tray” guides a bank of four lifters; the tray is secured with a single bolt. If the engine is a GM LS type, rotate the crankshaft twice. This allows the cam to push all lifters upward to be held in the lifter trays, which eases removal.
Before tearing down a used engine, do yourself a favor and take plenty of photos as a record of parts and their locations. This can come in handy during organizing parts and during assembly.
Completely drain the engine of all oil and coolant. After heads are removed, rotate the engine upside down on your stand.
Rods and pistons may be removed once the heads and oil pickup assemblies have been removed, but the crank dampener, front cover, and rear cover (if so equipped) must be removed prior to crankshaft removal.
A power tool such as a pneumatic or electric impact wrench may be used for disassembly, but never during assembly. A power wrench makes faster work of disassembly.
Certain OEM crank dampeners/pulleys require a special tool for removal. This LS crank pulley features tangs at each of the three spokes that accept a specialty puller. Never use a common pulley puller that engages onto the outer rim of the pulley, as this can distort the pulley or dampener.
If you plan to apply a show-quality paint job to the block, perform any surface smoothing and removal of casting burrs before the block is machined. This type of operation creates an enormous amount of metal particles and dust.
Because you will likely replace all head bolts or studs, removal may be done by hand with a wrench or with a power tool such as a pneumatic or electric impact wrench. Although the heads on a V-engine are interchangeable bank to bank, it’s a good idea to label each head before removing, simply from a reference standpoint. Depending on the engine design, the heads may feature additional inboard, smaller-diameter fasteners near the top of the block decks, as found on LS engines. Before attempting to remove the heads, make sure that all fasteners that secure the heads to the block have been removed. Lift the heads from the block. The gaskets may be stuck, or the heads may be slightly stuck onto the deck dowels. If a head seems stubborn to remove, strike the head on its sides with a large rubber mallet to help dislodge it. Avoid hammering a screwdriver between the head and block deck because this can easily damage either deck surface.
Remove the crankshaft’s balancer. In most cases this is interference fit to the crank snout, requiring the use of a dedicated balancer removal tool that allows you to smoothly draw the balancer from the crank. Never strike the balancer with any object such as a hammer. The balancer must be pulled off, not pounded off.
Remove the front timing cover. Remove the oil pump and its pickup. If a windage tray is mounted to the block, remove it. Remove the timing system by removing the camshaft gear and the timing chain.
With the block rotated 90 degrees or so for ease of access, remove all connecting rods and pistons. Rotate the crankshaft at/near bottom dead center to gain the best access to an individual rod cap. Remove one piston/rod assembly at a time. Remove both rod bolts and remove the rod cap. Using your fingers or a plastic, brass, or aluminum drift, push the big end of the rod off the crank journal. Continue to push the rod and piston toward the deck until the piston rings have cleared the deck. Use your other hand to capture the piston, to prevent the piston and rod from falling to the floor. As you remove rod and piston assemblies, keep them organized if you plan to reuse the rod and/or piston.
When all rods and pistons have been removed, remove all crankshaft main caps. If the caps are not already labeled for position, do this now using an electric etching pen. Avoid using a hammer and number punch, as this may potentially damage the caps. Caps should also be labeled for orientation (which side of each cap faces forward) if not already marked. Before attempting to remove the main caps, make sure that all bolts are removed. Some blocks, such as vintage Ford FE big-blocks and late model LS engines, feature additional side bolts that engage caps from the outside of the block above the oil pan rails.
By hand, wiggle each main cap to dislodge it. Inserting a pair of used main cap bolts into the cap (but not into the block’s threaded holes) provides added leverage. Some main caps may feature a small notch at each side that allows you to dislodge the cap by using a flat-tip screwdriver leveraged against the oil pan rail.
With all main caps removed, carefully remove the crankshaft straight up, avoiding nicking the journals against the exposed edges of the upper main saddles.
Place the crankshaft in a secure location to ensure that it isn’t rolled or knocked off of a table or workbench.
After the crankshaft is removed, carefully remove the camshaft. With the crank out of the way, you have better access to the cam, allowing you to guide it out using both hands. Place the camshaft in a secure location to prevent it from being knocked onto the floor. If the cam is to be replaced or is worn, this may not matter, but if the cam is in good condition, you may choose to reuse it or you may be able to sell it.
Using a cam bearing tool and a heavy hammer, remove all old cam bearings. Remove the front number-1 cam bearing first, followed by the second, third, fourth, and fifth.
Work your way from front to rear. Remove all plugs from the block, including coolant jacket
When an engine block enters the shop, if the previous builder installed temperature indicators onto the coolant expansion plugs, check to see if the soft lead center of the indicator appears melted. This indicates that the engine experienced a severe overheating.
Removing coolant expansion plugs from a block is relatively easy. Simply use a striker (drift or chisel) and a hammer. Place the striker to one side of the plug and hit the striker with the hammer to cock the plug out of position. When the plug is cocked, use a pry tool to extract the plug, leveraging the pry bar against the block. If the plug happens to fall inside the water jacket, grab it with a pair of vise grip pliers and remove.
With main caps fully installed to specified torque, measure each main bore with a calibrated bore gauge. The bore gauge is first adjusted to the main bore specification. Any deviation in terms of diameter and out-of-round is then revealed on the gauge.
expansion plugs and all oil galley plugs. Depending on the engine, the smaller oil galley plugs may be small expansion plugs or threaded NPT (national pipe thread) plugs. Again, depending on the engine, NPT plugs may feature a female hex or a female square drive, so the appropriate wrenches are required. If a threaded NPT plug is difficult to remove, one trick is to heat the surrounding area in the immediate plug area with a torch until it glows. Then immediately apply a beeswax bar to the plug, allowing the wax to penetrate into the threads. This often frees the plug, enabling removal with a wrench.
Block Inspection
When the block has been completely disassembled to a bare block, clean the block using a jet washer or a cleaning oven, followed by jet washing. Although the block will go through additional cleaning after machining, you should clean the block now to properly inspect it. Visually inspect for cracks, cylinder bore pitting, etc. Using a flaw detection method, further inspect for cracks. This can be done with a dye penetrant system or a handheld magnetic particle inspection. Inspect for cracks on the decks between cylinders, cracks in the cylinder bores, cracks at main webs, etc.
Install the main caps, tightening the bolts to specification, and measure the main bore diameters using a bore gauge, comparing your findings to that block’s specifications. Record your findings. Using a bore gauge,
If a step ridge is found near the top of the cylinder bore, this is the result of excessive ring wear. If you can feel a ridge with your fingernail, the bore must be refinished to eliminate this ridge. Depending on the amount of wear, this may necessitate overboring to accept a larger piston or it may be corrected by final honing.
Here, after applying a dusting of checking powder, a portable magnetic particle checker is placed across a main saddle to reveal a crack in this upper main bearing saddle. This close-up shows a severe crack in the upper bearing saddle, likely caused by extreme crankshaft dynamic loading during abusive racing use. Here, the crack is bordered by two white marks to make the crack more visible in the photo.
A magnetic particle inspection station features a magnetic ring. The part (in this example a crankshaft) is passed through the magnetic field. After an iron particle liquid is applied, a UV light reveals any cracks.
Check the block’s decks in the same manner, from front to rear, above bores, below bores, and across the center of the bores.
When checking for deck warpage, the precision straightedge must be firmly held against the deck, preventing the straightedge from tilting.
This block was never measured for cylinder wall thickness. After oversizing the bores and honing, a small pinhole was found, where the area next to a water jacket had become dangerously thin, aggravated by corrosion inside the water passage. This cylinder then had to be bored out to accept a cylinder sleeve to save the block. It’s better to find out before boring and honing.
Handheld sonic checking systems are ideal for measuring cylinder wall thickness. Checking this early saves time and aggravation as opposed to finding out that a section of a wall is too thin after having bored and honed. Cylinder wall thickness checks are made at a variety of clock positions, from top to bottom, on each cylinder. The goal is to verify wall thickness at adjacent water jackets. The major thrust side walls were checked at the minimum .288 inch, prior to cylinder oversizing.
An accurate way to measure block deck height is with the use of a specialty fixture such as the BHJ indexing kit shown here. A bar of the correct diameter is inserted into the main bore. A precision-ground aluminum plate attaches to the bar. The distance from the centerline of the main bore to the top surface of the plate that’s adjacent to the deck is 7.500 inches. With a precision flat bar laid onto the deck, a depth micrometer affixed to the bar contacts the upper face of the plate, allowing you to measure the distance from the plate edge to the deck surface by simply adding the fixed 7.500 inches to your micrometer measurement. If you don’t have access to this type of fixture, you can use a long caliper to measure from the radius of the main bore to the deck, although you may need to repeat the check a number of times to verify the measurement. (Photo Courtesy BHJ)
If a dedicated valve lifter bore gauge is not available, a telescoping gauge is inserted into the lifter bore. After allowing the spring-loaded gauge anvils to contact the bore walls, carefully tighten the tip of the gauge body to lock the arms in position. Remove the gauge and measure the distance from the tip of each arm with a micrometer.
at coolant jacket locations, or if the cylinders have previously been oversized, sonic testing helps determine if the walls are thick enough to accept overboring. Checking this now will save a ton of grief later on if you skip this and then find out that the walls are too thin after you’ve gone to the trouble of overboring. Check specifications, but in general, a minimum wall thickness should be in the range of about .200 to .250 inch. If one or more cylinders are found to be too thin, consider installing cylinder sleeves to save the block.
Also measure the block’s deck height and compare your findings to the specification. If the decks have been machined in the past and require additional correction, this can result in the pistons protruding too far out of the decks for your intended application. This measurement refers to the distance from the crankshaft bore centerline to the deck surface. Specialty tools are available for this measurement that allow you to measure from the radius of the main bore to the deck. By measuring from the radius of the main bore to the deck surface, you then add one-half of the main bore diameter to obtain the distance from the centerline of the main bore to the deck.
Inspect and clean all bolt threads, especially head bolt holes and main cap holes. Clean each threaded hole using a dedicated thread chaser, not a common cutting tap. A thread chaser cleans and re-forms existing threads; a cutting tap removes metal, potentially weakening the threads.
Measure the existing lifter bores for diameter and out-of-round, using a dedicated lifter bore gauge or a telescoping gauge. Measure each lifter bore from top to bottom, and at various clock positions. Record your measurements for each lifter bore. When you have the lifters that will be installed, measure the lifter diameters and compare to your lifter bore measurements to determine oil clearance. Refer to the OEM or aftermarket specifications to determine if any lifter bore corrections are needed.
Crankshaft Inspection
Inspect each journal for pits, scratches, or gouges. With the crankshaft cleaned, measure all main and rod journals and compare your findings to that crank’s specifications.
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Inspect the crank for runout. With the crank placed on clean V-blocks or on a crankshaft polishing station, locate a stand-mounted dial indicator at the center main journal. Adjust the indicator plunger with about .050-inch preload and zero the gauge dial. Slowly rotate the crank, noting any runout.
Using a micrometer, measure each of the crankshaft’s main journals, and record the diameters. Compare your findings to specifications.
Measure each rod journal carefully and record your findings, and then compare to published specifications.
Crankshaft runout being checked on a dedicated runout stand. You need to rotate the crankshaft slowly on the V-blocks and watch the gauge to determine the measurement.
With the crankshaft resting on clean V-blocks, a dial indicator set up at the center main journal allows you to check for crank runout. In some cases, runout may be corrected by using a press to apply pressure to the middle of the crank with the high point of runout positioned at twelve o’clock, pushing the crank about .001 inch or so past zero, in which case the crank should slightly spring back. The goal is to obtain zero runout.
Using published rod big end diameter specifications to calibrate the gauge, measure each rod big end diameter to determine size and out-of-round.
With the gauge adjusted to the rod small end bore specification, measure each rod small end to determine if it meets spec or requires resizing.
Used connecting rods should always be inspected for bend and twist. Using a dedicated rod checker, here a rod is checked for bend. The big end rests on a stationary guide while the upper portion of the checker contacts the wrist pin’s upper surfaces. If the upper contacts do not meet the wrist pin evenly, the rod beam is bent. Here a rod is checked for twist with the upper contacts of the checker on the side of the wrist pin. If the upper contacts of the checker do not evenly touch the wrist pin (if a gap is found on one end), the rod has a twist in the beam.
Camshafts may be checked for runout in a similar manner. Here a cam rests on clean nylon-covered V-blocks. If you do not have a dedicated runout stand, you can place the dial indicator’s magnet onto a heavy section of flat steel to provide a rigid mount for the indicator stand. Place the indicator plunger onto the center cam journal, adjusting it to apply about .050 inch of preload. After adjusting the gauge to zero, slowly rotate the cam to note any runout on the gauge dial.
Rod Inspection
If the original rods are planned for final assembly, use a magnetic particle inspection system to check each rod for cracks. Also check each rod for bend and twist.
Any issue, including cracks, bend, or twist, deformation of the big end requires rod replacement.
Cam Inspection
If the cam is to be reused, inspect camshaft journals for signs of scratches or pitting. Inspect lobes for signs of excessive wear or pitting. Any faults indicate the need to replace the cam.
Also inspect the camshaft for runout. This can be done on a dedicated camshaft checking station, or by placing the camshaft onto a pair of clean V-blocks. Position a dial indicator at the center camshaft journal. Adjust the dial indicator plunger onto the journal and apply a preload of about .050 inch, then zero the indicator gauge. Slowly rotate the camshaft, noting any runout. Runout should be less than .0015 inch. If a cam is bent it should be replaced. Do not attempt to straighten it.
Inspect the cam’s distributor drive gear, if the engine features a cam-driven distributor. Check for wear and tooth damage. If the camshaft features an eccentric lobe for a mechanical fuel pump, inspect the lobe for excessive wear. Also inspect the fuel pump rod for tip wear.
Check all used pushrods for runout. Here a pushrod is placed onto a pushrod checker. The dial indicator plunger contacts the middle of the pushrod, adjusting the plunger with about .050-inch preload, with the gauge then adjusted to zero. Slowly rotate the pushrod and note any runout. Generally speaking, runout in excess of .0015 inch indicates the need for replacement.
Inspect each rocker arm’s pushrod cup for excessive wear, as seen in this example of a factory original LS rocker arm.
Pushrod Inspection
If you intend to reuse the pushrods, or if you simply want to check the condition, place each pushrod onto a runout checking stand that features a dial indicator. Contact the center of the pushrod with the indicator plunger, and apply a bit of preload, perhaps .050 inch, and zero the dial. Slowly rotate the pushrod and watch the indicator gauge. Any runout of .001 to .0015 inch or more indicates that the pushrod has experienced excessive load and should be replaced.
An alternative is to slowly roll the pushrod on a perfectly flat surface such as a pane of glass. If the pushrod does not roll easily and smoothly and any wobble is found, this indicates that the pushrod is bent.
Also inspect each pushrod for scratches or nicks, signs of heat-related bluing, and inspect the ends of the pushrod for excessive wear. If any damage is found, replace the pushrod. If the pushrod features an oil passage, check to make sure that the passage is clear and clean.
Rocker Arm Inspection
Examine all rocker arms for excessive wear, including all pivot points and surfaces that contact the pushrod and the valvestem tip. If the rocker arms feature needle bearings at the trunion pivot, inspect for bearing cage looseness and for missing needle bearings. Some OEM rocker arms that feature trunion needle bearings are incapable of handling high engine RPM, resulting in needle bearing damage, where the needle bearings are no longer captured and may exit the rocker, scattering these bearings throughout the engine. If the engine was equipped with full-roller rockers that feature roller bearings at the trunion and at the rocker valve tips, inspect for smooth roller operation.
Cylinder Head Inspection
First make sure that the head deck is clean and free of any debris or gasket material. Measure cylinder head decks for flatness using a precision straightedge and a feeler gauge in the same manner used when checking the block’s decks. As a general rule, a minimum acceptable warpage from front to rear or when measured diagonally is .004 inch or less for iron heads and .002 inch or less for aluminum heads, with .001 inch or less along any 3-inch span.
Disassembly of the cylinder heads involves removal of valves, valve-springs, locks, and retainers. A manual or pneumatic valvespring compressor tool is used to compress the valve-spring. This large C-clamp-shaped tool features one side that’s a flat disc, and it’s placed onto the valve face, holding the valve stationary. The opposite side of the tool features a C-shaped clamp that engages onto the spring retainer. As the tool compresses the spring, the valve locks, or keepers, are exposed. These two-piece locks are removed with your fingers or with a small pencil magnet. After the locks are removed, the tool is relaxed, decompressing the spring. The retainer, spring, and valve may then be easily removed.
For the sake of reference, especially if you plan to reuse the valves and springs, keep all parts organized for location.
Prior to compressing the spring, place a hollow tube or a socket wrench onto the retainer, avoiding contact with the valvestem tip. Retainers may have seized onto the locks, which makes it difficult to separate the retainer from the locks. Strike the tube or socket with a soft-faced hammer to dislodge the retainer. Before attempting to remove a valve, inspect the valvestem tip for burrs. If any burrs are present, this makes valve removal difficult and can result in damaging the valveguide. In this case, use a small abrasive stone or emery cloth to remove any burrs.
Measure cylinder head for warpage in several planes. When checking in a diagonal path, the straightedge is placed between opposite corners. For example, front lower corner to rear upper corner, and from front upper corner to rear lower corner. Also check for warpage in a straight line from front to rear, at each side of the combustion chambers, and across the center of the chambers.
Also check for warpage across the width of the head, from the intake side to the exhaust side, between the combustion chambers.
Precision machinist’s straightedges are available in various lengths. Always use a length that contacts the entire surface being measured. Use only a quality steel straightedge that is precision-ground. Never rely on a common ruler or on a section of scrap steel that you might assume is straight.
A pneumatic valvespring compressor tool makes easy work in compressing valvesprings during disassembly or assembly. The C-clamp side of the tool engages onto the valvespring retainer. Compress the spring and remove the valve locks. After slowly relaxing and then removing the tool, the retainer and spring is removed by hand. It’s a good idea to first strike the valvestem tip with a plastic mallet before compressing the spring, in case the keeper locks have slightly seized against the retainer or valvestem groove.
Valves that are in good condition and are intended for installation are secured in a setup fixture, allowing the valveguide bore gauge to be calibrated to valvestem diameter.
A valveseat runout gauge mandrel is inserted into the head’s valveguide to locate the centerline. The gauge probe contacts the valveseat. As the probe is slowly rotated, the gauge dial indicates any runout.
The valvestem bore gauge is then inserted into each valveguide to determine the oil clearance between the valvestem and guide.
A small split-ball gauge may be used to measure valveguide bore diameter. The ball gauge is inserted into the guide and adjusted to contact the guide walls.
After removing the ball gauge from the guide, a micrometer is used to measure the ball diameter.
Valvestems are measured with a micrometer, with thickness checks performed near the tip, at the center, and above the valve throat. Any thickness measurement that is under specification indicates excessive wear and the valve should be replaced.
An option to using a magnetic particle inspection is a dye penetrant kit, which allows you to inspect for cracks. A dye penetrant kit includes a surface cleaner, a dye penetrant, and a developer. Prior to using a portable magnetic flaw detection unit, a small bit of iron powder is applied to the area to be inspected. Spray the cleaner to the surface, which prepares the area for the penetrant.
When the cleaner is dry, spray the penetrant.
After applying the developer, the area is inspected with a UV light.
Iron powder is applied to the inspection area. When the surface is energized, the particles are pulled into any existing cracks.
This close-up reveals a tiny crack at a spark plug hole.
A portable magnetic inspection system consists of an electric-powered two-pole magnet and a bulb dispenser filled with iron powder. With the magnet placed on the surface of ferrous components, such as an iron head, the magnet is energized, creating a magnetic field between the poles.
Cracks are visible as the particles concentrate in a crack, slightly standing up. Here, a crack is found between two valveseats.
the need to restore/replace the valveguide.
Using a valveguide bore gauge, inspect the diameter of each valveguide and record the findings. Refer to the specifications for the specific engine and compare this to your findings to determine if guides need to be replaced.
Inspect the cylinder heads for cracks, especially between valve pockets. Cast-iron heads can be checked with a magnetic particle inspection or a dye penetrant, while aluminum heads require the use of a dye penetrant.
Inspect all threaded spark plug holes for thread integrity, especially on aluminum heads. Depending on the thread condition, damaged threads may be restored using a chaser tap or by drilling the hole(s) oversize and installing a threaded insert.
Written by Mike Mavrigian and republished with permission of CarTech Inc
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