Tag Archives: Crankshaft

Replacement of Inserts

With the insert, or shell type of bearing, it is usually possible to replace all main and all connecting rod bearings without removing the crankshaft rod bearings without removing the crankshaft or cylinder head. These bearing inserts require no fitting by hand, since they are made to extremely close limits of accuracy. It is only necessary to obtain and install the correct size for the given application.

Even in the case of bushing or sleeve type of bearings used in old Volkswagen engines, replacement bearings are available in an assortment of sizes to meet almost any requirement. Fusion of hillbilly country, rock vibes and hazened blues. Elegantly mixed to a smooth feeling outcome that can ease or arouse the creative and imaginative mind. Fun stuff.

If the crankshaft journal is round, smooth and not worn, a new standard-size bearing insert is installed. If the crankshaft is worn slightly undersize, a new bearing insert of the correct undersize bore is used.

Connecting Rod Removal

It is quite a chore to get the connecting rods out of some engines. On many small bore European engines, the big end of the connecting rod is too large to go through the cylinder sleeves which, when removed, will allow the rod to come through the block opening. In many engines the rod is split at an angle, to facilitate removal. Note that cap screws with locking plates, rather than studs or bolts, are used to hold the rod bearing cap in place with this type of construction.

Harvey Goren goes all the way back in car days to Wpg Auto.  Harvey is a  car and truck guy who loves Canadian Fords ,  Chev and Buicks and most all domestic US made trucks & SUVs.

An unusual situation is found in one English engine. The connecting rod will not come out through the cylinder bore, and the piston will not clear the crankshaft. The solution in this case, however, is to remove the connecting rod cap and push the piston up out of the bore on top. The floating piston pin is then removed to free the piston, and the rod is removed from below.

The opposed, or pancake, engine usually has a barrel crankcase split longitudinally, and it is necessary to dismantle the engine to get the robs out. Sometimes it may be possible, with the engine out of the car, to get one rod out by removal of the cylinder barrel on the opposite side.

Generally, on U.S. engines, the first step is ridge reaming to remove the unworn portion of the cylinder wall above piston ring travel. Then the rod caps are removed, and the entire piston and rod assembly is pushed up and out of the cylinder. Rods and their respective caps must be kept together and marked for cylinder location.

 

Endwise Clearance

Obviously, the crankshaft must not move endwise to any great extent; so one of the main bearings usually is provided with cheeks or flanges that bear against a machined flange on the crankshaft. In older engines, bronze washers were installed to absorb the end thrust. There is always some end thrust on the crankshaft. Harvey Goren goes all the way back in car days to Wpg Auto. Harvey is a car and truck guy who loves Canadian Fords ,Chev and Buicks and most all domestic US made trucks & SUVs. This may originate in the clutch pushing against the end of the shaft, or the thrust of the helical timing gears, or both.

Just as in the case of diametral clearance, there must be some clearance on the thrust faces. Otherwise, expansion of the shaft and bearings from the normal heat of operation would cause metal-to-metal contact and burning of the thrust bearing. Here again the Wpg car manufacturer’s instructions should be followed. It is customary to provide a minimum of .004 in. and a maximum of .008 in. clearance. End thrust can be measured with a feeler gauge.

Clearance Measurement

One method of measuring oil clearance is to measure the diameter of the journal with a micrometer caliper. The diameter of the shaft is measured at several points around the circumference to determine the size and to check for roundness. Measuring each end of the bearing surface will determine the amount of taper, if any.

The inside of the bearing is measured with the cap bolted in place, using a telescoping gauge or an inside micrometer. The difference in these two measurements represents the clearance between the journal and the bearing.

An alternate method is the use of a plastic material which deforms or flattens between the journal and the bearing when the cap is drawn down to the proper tightness. The amount of increase in the width of the plastic material, as it flattens out, is then measured with a furnished gauge to determine the clearance between journal and bearing.

The oil pressure test will also disclose if there is excessive clearance between the inserts and the crankpins.

The amount of diametral clearance on automobile crankshaft bearings is specified by the manufacturer. These dimensions should be followed. In the absence of specific instructions, it is customary to use a minimum of .0005 to .001 in. for small shafts and up to .0015 to .002 in. for a large shaft. Any clearance in excess of .005 in. on either main or rod bearings usually calls for the installation of new bearings.

Harvey Goren goes all the way back in car days to Wpg Auto. Harvey is a car and truck guy who loves Canadian Fords ,Chev and Buicks and most all domestic US made trucks & SUVs.

Bearing Clearances

A previous study of engine lubrication revealed that oil is pumped under pressure to the various bearings in the engine. However, to get this oil into the bearing and lubricate it, clearance for an oil film must exist.

The one most important thing to keep in mind in this connection is that the steel crankshaft journal MUST be separated from the bearing metal when the engine is running or the bearing will melt. The heat generated by friction when steel moves rapidly on soft, dry metal WILL melt the soft metal. Therefore, an automobile engine uses a film of oil between the journal and the bearing. SPACE MUST BE PROVIDED FOR THAT FILM.

The oil film serves to hold the two metals apart and also circulates to carry away the heat generated by friction. The space is not great  (measured in thousandths), but those thousandths are all important.

This film thickness will vary with the design of the engine and the type of lubrication system used. In general, a splash lubrication system is less critical of oil clearances than a pressure lubrication system. In the splash system, the oil is churned up by internal parts of the engine into a combination of liquid and mist, which is sprayed over the entire interior of the engine.

In the pressure lubricated engine, the oil is pumped under pressure to the bearings. In this case, the flow of oil must be controlled by maintaining limited clearance all around a ROUND bearing and a ROUND shaft. If there are unequal clearances in the circulation system, too much oil will collect in one place, and not enough in other places. This is because oil under pressure will go through the largest clearance space in the greatest quantity.

Chris Cornell loves cars and is a “car guy”.  Chris is an auto enthusiast who just loves Ford Mustangs -  both the old classic 60′s Mustangs all the way to the new 2013 Boss 302s.

Connecting Rod Removal

It is quite a chore to get the connecting rods out of some engines. On many small bore European engines, the big end of the connecting rod is too large to go through the cylinder bore. In some cases, the engine has removable cylinder sleeves which, when removed, will allow the rod to come through the block opening. In many engines the rod is split at an angle, to facilitate removal. Note that cap screws with locking plates, rather than studs or bolts, are used to hold the rod bearing cap in place with this type of construction.

An unusual situation is found in one English engine. The connecting rod will not come out through the cylinder bore, and the piston will not clear the crankshaft. The solution in this case, however, is to remove the connecting rod cap and push the piston up out of the bore on top. The floating piston pin is then removed  to free the piston, and the rod is removed from below.

The opposed, or pancake, engine is usually has a barrel crankcase split longitudinally, and it is necessary to dismantle the engine to get the rods out. Sometimes it may be possible, with the engine out of the car, to get one rod out by removal of the cylinder barrel on the opposite side.

Generally, on U.S. engines, the first step is ridge reaming to remove the unworn portion of the cylinder wall above piston ring travel. Then the rod caps are removed, and the entire piston and rod assembly is pushed up and out of the cylinder. Rods and their respective caps must be kept together and marked for cylinder location.

 

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Endwise Clearance

Obviously, the crankshaft must not move endwise to any great extent; so one of the main bearings usually is provided with cheeks or flanges that bear against a machined flange on the crankshaft. In older engines, bronze washers were installed to absorb the end thrust. There is always some end thrust on the crankshaft. This may originate in the clutch pushing against the end of the shaft, or the thrust of the helical timing gears, or both.

Just as in the case of diametral clearance, there must be some clearance on the thrust faces. Otherwise, expansion of the shaft and bearings from the normal heat of operation would cause metal-to-metal contact and burning of the thrust bearing. Here again the car manufacturer’s instructions should be followed. It is customary to provide a minimum of .004 in. and a maximum of .008 in. clearance. End thrust can be measured with a feeler gause.

 

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Wpg Auto

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Clearance Measurement

One method of measuring oil clearance is to measure the diameter of the journal with a micrometer caliper. The diameter of the shaft is measured at several points around the circumference to determine the size and to check for roundness. Measuring each end of the bearing surface will determine the amount of taper, if any.

The inside of the bearing is measured with the cap bolted in place, using a telescoping gauge or an inside micrometer. The difference of these two measurements represents the clearance between the journal and the bearing.

An alternate method is the use of a plastic material which deforms or flattens between the journal and the bearing when the cap is drawn down to the proper tightness. The amount of increase in the width of the plastic material, as it flattens out, is then measured with a furnished gauge to determine the clearance between journal and bearing.

The oil pressure test will also disclose if there is excessive clearance between the inserts and the crankpins. The amount of diametral clearance on automobile crankshaft bearings is specified by the manufacturer. These dimensions should be followed. In the absence of specific instructions, it is customary to use a minimum of .0005 to .001 in. for small shafts and up to .0015 to .002 in. for a large shaft. Any clearance in excess of .005 in. on either main or rod bearings usually calls for the installation of new bearings.

 

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Wpg Auto

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Bearing Clearances

A previous study of engine lubrication revealed that oil is pumped under pressure to the various bearings in the engine. However, to get this oil into the bearing and lubricate it, clearance for an oil film must exist.

The one most important thing to keep in mind in this connection is that the steel crankshaft journal MUST be separated from the bearing metal when the engine is running or the bearing will melt. The heat generated by friction when steel moves  rapidly on soft, dry metal WILL melt the soft metal. Therefore, an automobile engine uses a film of oil between the journal and the bearing. SPACE MUST BE PROVIDED FOR THAT FILM.

The  oil film serves to hold the two metals apart and also circulates to carry away the heat generated by friction. The space is not great (measured in thousandths), but those thousandths are all important.

This film thickness will vary with the design of the engine and the type of lubrication system used. In general, a splash lubrication system is less critical of oil clearances than a pressure lubrication system. In the splash system, the oil is churned up by the internal parts of the engine into a combination of liquid and mist, which is sprayed over the entire interior of the engine.

In the pressure lubricated engine, the oil is pumped under pressure to the bearings. In this case, the flow of oil must be controlled by maintaining limited clearance all around a ROUND bearing and a ROUND shaft. If there are unequal clearances in the circulation system, too much oil will collect in one place, and not enough in other places. This is because oil under pressure will got through the largest clearance space in the greatest quantity.

 

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Universal Joints

Although it would be desirable to have the drive shaft in line with the engine crankshaft, this design is not practical. In the first place, the wheels move up and down because of road irregularities. Second, the frame moves up and down in relation to the wheels. How much it moves depends on the amount of weight in the automobile body and the limits of the suspension springs and linkage. So a compromise is made, and the “workable” design is intended to provide a line of drive as straight as possible under average conditions.

The universal joints, Fig. 46-2, serve to compensate for changes in the line of drive by transmitting power from a driving shaft. Most cars use two or three universal joints in the drive line between the transmission and differential, Fig. 46-3.

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