Tapping the crank question
08-18-2008, 02:30 AM
#1
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Tapping the crank question I know that your supposed to tap the crank backward and then forward to align the thrust bearing. How critical is it to actually tap the crank backward and forward? I mean it doesn't seem like it will affect the location of the cap whatsoever. There's really only one place the thrust bearing cap can even sit.
The reason I ask is because when I originally reassembled my motor I did the crank tap but then I found out I had the wrong length connecting rods. So I had to re-reassemble the motor again with the correct rods but the second time around I neglected to tap the crank. The motor is already back in the car and all bolted up. Is this a case of pulling the motor and disassembly again just so I can take off all the caps and tap the crank with a plastic hammer? I really need to know some input on this!
Thanks!
The reason I ask is because when I originally reassembled my motor I did the crank tap but then I found out I had the wrong length connecting rods. So I had to re-reassemble the motor again with the correct rods but the second time around I neglected to tap the crank. The motor is already back in the car and all bolted up. Is this a case of pulling the motor and disassembly again just so I can take off all the caps and tap the crank with a plastic hammer? I really need to know some input on this!
Thanks!
08-18-2008, 08:35 AM
#2
You tap the crank back and forth to get the clearance on the trust bearing, so you can take a filler gauge to check the clearance. Tap the crank forward and then check the clearance between the crank and main cap, This so you can see how much the crank is walking in the block.
08-18-2008, 08:40 AM
#3
This is not a LS1 but is the same method
Checking Crankshaft End Float (Thrust Clearance)
Wear at the main bearing flanges or thrusts should be checked. Only one main bearing position takes the thrust loading and this bearing may be located at the front, centre or rear, depending on the engine design.
To check end float (thrust clearance), pry the crankshaft forward as far as possible, then insert a feeler gauge between the front flange of the bearings and the mating crankshaft thrust surface, as shown in Fig. G, or set up a dial indicator to measure the end float see Fig. H
Fig. G Checking the end float with a feeler gauge.
Fig. H Checking end float with a dial gauge.
It is advisable to check end float at both front and rear to ensure an accurate measurement.
End float varies with different engines, however the following is a table of recommended end clearances, if the manufacturer's specifications are not known.
Checking Crankshaft End Float (Thrust Clearance)
Wear at the main bearing flanges or thrusts should be checked. Only one main bearing position takes the thrust loading and this bearing may be located at the front, centre or rear, depending on the engine design.
To check end float (thrust clearance), pry the crankshaft forward as far as possible, then insert a feeler gauge between the front flange of the bearings and the mating crankshaft thrust surface, as shown in Fig. G, or set up a dial indicator to measure the end float see Fig. H
Fig. G Checking the end float with a feeler gauge.
Fig. H Checking end float with a dial gauge.
It is advisable to check end float at both front and rear to ensure an accurate measurement.
End float varies with different engines, however the following is a table of recommended end clearances, if the manufacturer's specifications are not known.
08-18-2008, 10:48 AM
#4
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So basically tapping the crank is just to verify crank clearance or how much it's going to "walk" in the block forward or backwards...is that right? If my machine shop did all the clearancing etc then should I be really worried about tapping the crank myself?
08-18-2008, 03:20 PM
#6
Well, it's also to make sure that the thrust surface of the thrust bearing is pushed forward as much as possible, to make good contact with the block and cap. If it's not, when you press in the clutch, you may start getting uneven wear on the thrust bearing, because only part of it will take most of the load.
