Original-equipment Ford FE crankshafts were made from either cast-nodular iron or forged steel. The nodular-iron cranks have proven to be extremely durable and are found in the majority of production engines. A steel crankshaft is inherently superior, especially in severe service where exposed to extremes in terms of power or cycle fatigue. A road-race engine is exposed to extreme cycle fatigue because it is subjected to long periods of heavy throttle and transitional loading. A steel crank is ideally suited for this application. On the other hand, a cast-nodular-iron crank is perfectly adequate for the budget-constrained, street-oriented builds and many drag-race applications because these cranks are typically subjected to full-throttle operation for shorter periods of time. By far most FE builds will use a cast-iron crankshaft.
Steel crankshafts were installed in the always-rare 427 performance engines with their 3.780-inch stroke and in medium-duty truck 361 and 391 engines. The limited supply of factory 427 steel cranks in repairable condition drove their cost beyond the reach of many engine builders several years ago. There are a few NASCAR 427 steel cranks that use a wider connecting rod and bearing than common OEM equipment. With these supporting parts being nearly unobtainable, the NASCAR cranks are best left in the hands of collectors who have a demonstrated need for such parts.
FE Ford engines used a wide variety of crankshafts over the production life of the engine. All of them can be physically installed in any FE block. The most popular cast cranks were offered in strokes of 3.50 for the 352 and 360 engines; 3.78 for 390, 406, and 427 engines; and 3.98 stroke in the 410 and 428. Steel crankshafts were available only in the 3.78-stroke 427 engines for passenger car use, and in 3.50- and 3.78-stroke versions for medium-duty and heavy-duty trucks.
The steel 427 crankshaft pictured is both rare and expensive. Compared to the 427 unit, the steel truck crankshafts have completely different snout dimensions and counterweight designs. The easier-to-find truck cranks can be converted to passenger car and racing use by a skilled crank grinder. Before aftermarket crankshafts came onto the market, this was a common task for performance use.
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Once you’ve seen an FE crankshaft, it’s pretty easy to pick out another one among any collection of parts. They have a unique, long front snout similar to that of the 429/460 parts, but are much smaller in main journal and counterweight size.
This is a factory original 1969 390 crankshaft removed from an engine with 11,000 miles on it. You can clearly see the various factory paint markings as well as a balance hole in the rear counterweight.
Cast cranks such as this one can easily be identified by the thin-cast parting line running the length of the crank, as opposed to the thicker line of a steel crank.
The 3.780-inch-stroke steel 391 truck crankshaft can be converted into a performance piece. The truck crankshaft has a larger-diameter snout where the dampener mounts, as well as a different flywheel mounting flange and a counterweight combination designed for external balance. The pilot-bushing (or converter snout) hole in a steel truck crankshaft is larger in diameter as well, mandating a custom pilot or converter bushing for use in passenger car applications. The crankshaft nose needs to be cut down to the standard 1.375-inch FE diameter, the flywheel mounting surface is shortened by about .060 inch, and the counterweights need to be cut down before balancing is possible. The supply of usable 391 cores has also dwindled in recent years, increasing the cost of the finished product, but this remains a viable option for those needing a steel crank within the stock stroke ranges at half the cost of a custom billet. The required modifications are time consuming, but a skilled crankshaft shop can handle them.
Identification
By far the most common factory offerings were the 3.50-inch-stroke cast crankshafts found in 352 and 360 engines and the 3.78-inch-stroke cast units common to 390s. The highly sought-after 3.98-inch-stroke cranks were used only in 428 applications and for two years (1966–1967) in Mercury 410 engines. A few of the 428 crankshafts have different center counterweights and were specified for vehicles equipped with the Super Cobra Jet (the “Drag Pack” option). Your odds of finding one of them in a normal swap meet or junkyard are slim.
It’s a fair bet that the average FE crankshaft you find in a parts pile or swap booth will be a cast 390 or 360 piece. If you are really lucky, you may find a 428 crank. A steel truck crankshaft occasionally shows up, but most often they have been turned .030 or .040 under. A serviceable steel 427 crank is extremely difficult to find outside of Ford specialty retailers or among dedicated racers.
It’s fairly easy to tell a cast crankshaft from a steel one. The cast crank has a very thin parting line where the two halves of the mold meet one another. In comparison, the steel crankshaft has a thicker parting line, usually between 1/4 and 1/2 inch wide.
In comparison, this is a factory Ford steel crankshaft. You can clearly see the far thicker parting line, which is characteristic of a forged part. Any of the forged crankshafts will have this physical feature.
The forged steel 427 crankshafts often have the somewhat appropriate “$” on them. The original part number will often be partially ground off; that is normal for these and not an indication of modification.
This is a 428 crankshaft with the 3.98 stroke. All the 428 cranks (and only 428 cranks) will have a “1U, 1UA, or 1UB” stamping on one of the counterweights.
Ford forges or casts numbers on the counterweights of the FE cranks, which may simplify identification. As is the case in most FE parts, the numbers are helpful but not definitive. Often they are useful for exclusion; if a crank is stamped “2U” it’s obviously not a 428 part, but the absence of any stamping number does not preclude it from being one.
Here are some common casting marks; it’s by no means a comprehensive list:
• The cast 360 often has a 2T or 2TA
• The cast 390 often has a 2U or 2UA
• The cast 428 has a 1U, 1UA, or 1UB
• The cast 428 SCJ has a 1UA or 1UB
• The steel 427 may have a somewhat appropriate “$” sign
These parts are now 30 to 40 years old and have often seen a vast amount of modification, alteration, repair, and service. By far the best way to identify the crank is to measure the actual stroke using V-blocks or even an engine block with a couple main bearings set in it. The stroke variances are large enough that you don’t have to be perfectly accurate for basic ID; even a ruler does the job. It is around 3.5 inches for the 360, just more than 3.75 inches on the 390 cranks, and nearly 4 inches for the 428 version. The extra center counterweights on a 428 SCJ crank are obvious, as is the large 1.75-inch-diameter snout of an unaltered steel truck crank.
Measurement and Inspection
The most important descriptors for any crankshaft (OEM or aftermarket) are “solid,” “straight,” and “round.” These terms apply to the crank as a whole as well as to each individual journal.
Checking the crank for straightness can be done either on a set of V-blocks or, lacking those, you can use the block itself by cradling the crank with bearing shells in the front and rear journals only. Use a dial indicator on the center journal to see whether it’s straight or not. Try moving a bearing from one end to the center and rechecking at the end journal. While the factory-accepted tolerance per the book may be higher, anything beyond .0005 inch is a potential problem in an assembly where clearances less than .0030 inch are expected.
The same holds true for main and rod journals. These need to be checked in multiple places around each journal, and on at least a few spots front to rear. It is common to find a rod (or main) journal that has significant diameter differences forming either a tapered or barreled shape. Once again, any variance beyond a few ten thousandths of an inch can lead to early bearing wear or failure.
Check the journal diameters of the main and rod journals. These need to be checked in multiple places around each journal, and on at least a few spots front to rear. It is common to find a rod (or main) journal that has significant diameter differences forming either a tapered or barreled shape. Even new crankshafts can show variance in this area, and can be machined for uniformity.
When looking at potential crankshafts, take a quick look at the snout diameter, the condition of the keyway slot, and the threads for the damper bolt. While often repairable, damage in these areas often renders a crank financially unsound as a prospect. Compared to a passenger car shaft, a steel truck crankshaft snout is much larger in diameter, uses a much larger bolt, and would need modification to use in a car engine, which is an expense that falls outside the focus of this book.
Out-of-tolerance journals are common in used factory parts as well as brand-new items. You need to check. Your crankshaft machinist can grind to the next undersize if needed to straighten out a lot of these variances, a pretty common occurrence on even new imported crankshafts.
Additional dimensional specifications that must be considered include the rod journal width and main thrust journal width. Rod journal width, along with the dimensions of the chosen connecting rods, determines the rod side clearance. This is a more forgiving clearance with a broad acceptable range (.008 to .020 inch is common), but still something that needs to be validated during assembly. Thrust journal width can be compared to specs while actual thrust clearance, a critical dimension, cannot be determined until the crank is installed in the block with the chosen bearing.
Cranks should be checked for cracks using Magnaflux equipment. While a good idea for any part, this is particularly important when reusing a cast crank because it is very common to find fatigue cracks around the rod journal radii alongside the counterweights. Sometimes these are surface flaws that can be removed by grinding down to the next undersize, sometimes not.
Throw index and stroke variance are less often checked in the typical home engine build, but the latter, in particular, can be important to determine. If you’re not paying attention, it can “catch you,” and the consequences are catastrophic. A lot of folks target a near-zero deck clearance on their engine project, simply adding the nominal dimension of connecting rods, pistons, and crank stroke, and then machine the block decks to the combined value. Differences in stroke measured from journal to journal of .001 inch or more are not unusual, and I’ve seen more than .005 inch on some import crankshafts. A bit too much will impact compression ratio, piston-to-valve clearance, and piston-to-deck clearance.
Before you pronounce your crankshaft candidate a winner, take a quick look at the snout diameter, the condition of the keyway slot, and the threads for the damper bolt. While often repairable, damage in these areas often renders a crank financially unsound as a prospect. With the cost of a usable or repairable 390 crankshaft being under a couple hundred dollars it does not make sense to spend too much on repairs.
Grinding and Polishing
Once you’ve decided to move ahead with your crankshaft, it’s time to take it to a machinist who has the specialized equipment needed to recondition it. Many automotive machine shops will send their crankshaft work out to a specialist because of the cost of the equipment and the skills needed to do the job correctly.
The crank grinder is a large machine that uses abrasive wheels to remove material from the journals, returning them to a factory finish, but at a smaller diameter. On older engines such as the FE Ford, it is common to finish them to progressively smaller diameters in increments of .010 inch; hence, a crankshaft with both main journals and rod journals reduced by ten one thousandths of an inch will be referred to as “10-10.”
After the journals are ground to size, they need to be polished to establish a good surface finish for the bearings to work with. The surface finish left by the grinding stones would be too rough and cause premature wear. The polishing is done with an abrasive belt, which removes very little material. After polishing, the crankshaft is ready to be thoroughly cleaned. Concentrate on running a brush through all of the oiling passages. Once it is cleaned, you can spray some preservative oil on it and put it into a bag to keep it safe until balancing and assembly.
Balancing
We are going to briefly cover balancing here, although it is normally one of the last steps before assembly. A big piece of balance work is focused upon the crankshaft. While balancing is not mandatory on a mild stock rebuild, it is usually a very good idea on any engine that is going to stray from factory weights or dimensions of parts.
Most FE Ford engines are internally balanced. This means that the flywheel and damper are balanced by themselves and have no effect on the balance of the engine itself. On 428 (and some medium-duty truck 391 engines) the balancing is external, requiring additional weight on the flywheel and sometimes the damper spacer. Those engines will need the flywheel and damper spacer installed on the crankshaft for balancing.
On 428 (and some medium-duty truck 391) engines, the balancing is external, requiring additional weight on the flywheel and sometimes the damper spacer. Those engines will need the flywheel (and possibly the damper spacer) installed on the crankshaft for balancing. Note the size of the weight on this flywheel. A 428 crankshaft can be balanced internally to permit use of a normal 390 flywheel, but doing so requires heavy-metal (tungsten) slugs, which can double the cost of balancing.
Balancing is not mandatory for a stock-type build. But it is very important when new parts are significantly different (often much lighter weight) from the original parts. When balancing, a precisely measured weight assembly is clamped to each rod throw. These weights simulate the rotating and reciprocating weight of the piston and rod assemblies.
The balancing machine will spin the crankshaft and weight assembly and provide a digital readout. The readout will indicate the weight of material that needs to be removed (or added), along with the location of the removal.
The thrust bearing on an FE is in the number-3 position in the middle of the block. I have seen folks accustomed to building other engines put these in the wrong location. Place the upper main bearing shells (the ones with the oil holes) in position in the block. They snap into place dry with no lubricant or adhesive of any sort on the backside of the bearing.
Bearing clearances are a critical measurement. The clearances published in most bearing catalogs are possible arithmetic ranges using parts that meet specification, and are not recommended targets. A good rule is to target .001-inch clearance per inch of journal diameter. A little bit tighter is safe on a street build, but you should always try to remain below .003 inch. The most accurate way to check main bearing clearances is with the use of a dial bore gauge. To use the dial bore gauge, first install the bearings and torque the main caps to specification without the crankshaft installed. If you are building a 427 with cross bolts, torque those as well; they do change bearing clearances.
Balancing involves a couple of steps. We have “rotating weight” and “reciprocating weight.” Rotating weight includes the large end of the connecting rods and the rod bearings. Reciprocating weight includes pistons, pins, rings, lock clips, and the small end portion of the connecting rods. All the weights used in balance calculations are given in grams: 454 grams equal 1 pound.
The first step is to weigh and match all the reciprocating components to one another. Pistons should weigh the same as each other, as should bearings, piston rings, and piston pins. The small ends of the rods should also match and can be ground if needed to get them corrected.
This Tech Tip is from the full book, FORD FE ENGINES: HOW TO REBUILD. For a comprehensive guide on this entire subject you can visit this link:
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The pistons in modern sets are usually very closely matched, while the other parts are near perfect. Pistons can have a small amount of material removed if necessary to equalize them, but this has become rarely necessary anymore.
With all the parts equalized, the weight values are input into a formula. The formula will provide a value that is referred to as the “bobweight.” The counterweights designed into the crankshaft need to offset the bobweight to achieve a smooth-running engine. A selection of weights is mounted to the crankshaft rod journals to replicate the bobweight, and the crankshaft assembly is spun on a sophisticated measurement machine called a balancer.
We use the balancing machine to measure the location and amount of material that needs to be removed or added to the counterweights to achieve this goal. To reduce weight we will drill holes into the counterweights. To increase weight we will need to press in slugs of tungsten, a heavy metal that weighs twice as much as steel.
Bearings and Assembly
With a completed and cleaned block and a reconditioned crankshaft ready, we can begin the assembly process. Normally, I install the camshaft first as a convenience since it’s easier to slide it into position before the crankshaft and connecting rods are in the way. We will be covering the camshaft selection in a subsequent chapter, so this is one of those sections where you will want to read ahead before starting. Make certain to use oil on the cam bearing journals and the appropriate break-in lubricant on the cam lobes.
The bearings are snapped into the main caps the same way: clean, dry, and with no sealer or anything between the cap and the bearing. The bearings in this picture are Federal-Mogul race bearings. They have that dark, burnt appearance new, out of the box. They deleted the cosmetic tin plate operation to achieve a stronger bearing alloy.
FE Ford main bearings are mostly interchangeable from year to year with a single notable exception. The outside diameter of the thrust bearing changed sometime around 1964. The later bearing will not fit the earlier block without modification. Many aftermarket bearings are now designed to fit both blocks.
My strong personal preference is to use either a 3/4-groove or 1/2-groove bearing on the mains. I actively try to avoid full-groove bearings. And I really dislike the idea of having an unnecessary “oil hole” in the lower main position, as is done on inexpensive bearing sets. I use the Federal-Mogul race bearings in all of my builds.
Bearing clearances are crucial to a successful build and should always be checked. Any of several methods may be used to verify bearing clearances. The best way to check these is with a dial bore gauge. A person working in a home shop might not have that tool available and will need to get by using Plastigauge. Any means of measurement is better than not checking. The clearance you are looking for is measured vertically since bearings change in clearance as they approach the parting lines. My preferred clearance range is between .0025 inch and .0030 inch.
Check Bearing Clearance—Micrometer
1 Use a micrometer to precisely measure each of the crankshaft’s journal diameters.
2 Put the micrometer into a vise or holding fixture, with it locked to that measurement that you just made.
3 The bore gauge is then set to read “zero” when it is slipped into the micrometer.
4 You then take the “zero’d” bore gauge and slide it into the bearing. It will give you a precise measurement of the bearing’s vertical clearance. Bearing clearances will vary around the diameter of the bearing, and are always measured at the vertical point.
Check Bearing Clearance with Plastigauge
1 If you do not have a dial bore gauge available, the next best thing is to use Plastigauge to verify clearances. This is a thin plastic strip that is compressed during a test assembly. You then read the thickness of the compressed plastic to get an indication of the assembly clearance. Not as good as a dial bore gauge, but far better than not checking.
2 To obtain a successful reading with Plastigauge you will set the lightly oiled crankshaft into the main saddles with bearing shells in place. Lay a single thread of the plastic on the journal to be measured, then install the main cap and torque it to specifications. It is important that you do not rotate the crankshaft at this point.
3 Carefully remove the main cap and you should have a clearly measurable strip of compressed flat plastic to make a reading. A thickness comparison chart is printed on the Plastigauge wrapper. Compare the width of the plastic strip to the chart to get a good approximation of bearing clearance. You will want to remove the plastic before continuing assembly. With some journal diameters you may have the option of alternate bearing sizes to adjust clearances. When available, it is perfectly okay to mix a +.001 or -.001 shell and a standard bearing shell on the same journal. In other cases you may need to have the crankshaft touch ground to gain necessary clearance if it is too small. If bearing clearances are acceptable, you may continue with assembly.
Final Crankshaft Assembly
1 You should always use a pre-lube or oil on the bearings where they meet the crankshaft during final assembly.
2 The back of the bearing that installs against the housing bore is left dry. No oil, adhesive, or sealer of any sort is desired in that location. But the crank surface always gets lubricated.Â
3 Install and torque bearing caps numbers 1, 2, and 4 first. The number-3 bearing on an FE engine is the thrust and requires extra attention. Lightly assemble that cap into place but do not fully tighten it. Use a large plastic dead blow hammer and give the crank a firm “knock” forward and backward to straighten and locate the bearing’s thrust surfaces. Use a large screwdriver or pry bar to push the crank forward and hold it there while tightening the number-3 main to specification.Â
4 Now you can mount a magnetic dial indicator to the front of the block and set it up to measure thrust clearance. You should be able to smoothly push the crank back and forth in the block and see somewhere in between .006 and .012 fore and aft thrust clearances.Â
5 Cap number-5 includes the rear main seal. Rear seal problems are very common with FE engines. We do follow a particular procedure when installing the rear seal and cap to minimize problems, but even the best efforts are subject to some degree of possible leakage. The rear seal itself has a pair of semicircular rubber seals that are installed into the block and the main cap with the sharp edge always facing inward toward the block. The seal is always lubricated during assembly; it cannot be allowed to run dry against the crankshaft.Â
6 Since the rear main seal area is the area that is least accessible after the engine is back in the vehicle, as well as most prone to leak, make sure this area is spotless before proceeding with assembly.Â
7 The Ford FE series of engine uses a conventional two-piece rear main seal. What is unusual is that the FE also uses a pair of vertical “side seals” that are slid into recesses in the main cap. I smear a very small amount of Motorcraft TA-31 silicone around the outer diameter of the main seal prior to installation.Â
8 Slide the upper rear main seal half into the block, with the sharp edge of the seal facing in toward the crankcase. Put a small amount of oil on the surface of the seal that will be riding against the crankshaft.Â
9 Instead of oil, use a small amount of Motorcraft TA-31 silicone as an assembly lubricant for both the rubber side seals and for the nails. The side seals are loaded into the grooves first, followed by a pair of nails that are driven into position in between the cap and the side seals to add pressure to the sealing surface.Â
10 Use a very thin film of the same silicone alongside the block sides and corners where the cap and side sealing surfaces meet. Slide the main cap into place as shown.
11 Once the main cap is lined up, install the main cap bolts, and slide all the way into place, making sure the side seals remain flush with the top main cap surface.Â
12 Once the main cap is fully seated, insert the side seal pins and tap them into place carefully. Their primary function is to tighten the seal against the mating surfaces of the cap and block. Do not force the pins; if there is interference, pull the cap back off to see why
13 The side seals and nails should be flush with or slightly below the oil pan gasket surface once everything is assembled. If done correctly you will see a tiny amount of silicone squeeze out between the main cap and the block along the sides and the cap register. This is the indication that you have completely sealed the voids at the rear of the block. Once the silicone has dried you can trim off any excess. The result should be a clean, flat surface for the oil pan gasket to seal against. A dab of silicone can fill a low spot and a razor blade can trim any protruding rubber.
When completely assembled, you should be able to rotate the crankshaft smoothly by hand with only a bit of drag from the rear seal. If it takes a lot of force (or a wrench) to turn the crank, you have a bearing clearance or alignment issue that needs to be resolved before moving forward.
Written by Barry Rabotnick and republished with permission of CarTech Inc
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