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question 95 impreza crank bolt
Posted 25 November 2012 - 02:44 PM
Posted 25 November 2012 - 03:29 PM
Depends on how bad keyway is how screwed you may be.
Posted 25 November 2012 - 03:29 PM
replace the missing pieces and any damaged or mutilates pieces, like the crank pulley and the crank sprocket.
the keyway in the crank may be mangled, but it should go back together and run right if you line it up correctly and torque it to 137 ft. lb.
also a good time to replace the timing belt and anything else needed inside the timing cover.
when was the timing belt last done?
this thing came apart because the bolt was too lose, not torque to spec. if you do not replace any mangled parts, except the crank, and if you do not torque it to spec, it MAY cause a repeat failure.
Posted 25 November 2012 - 05:36 PM
Posted 13 December 2012 - 10:01 AM
Posted 13 December 2012 - 11:58 AM
Posted 13 December 2012 - 04:30 PM
Posted 15 December 2012 - 07:53 PM
Posted 16 December 2012 - 08:38 AM
Posted 16 December 2012 - 11:14 AM
Posted 16 December 2012 - 12:26 PM
Holding the crank pulley with a tool is of course the best way to tighten the crank bolt. However, I easily held the motor with a 8" shank, 3/8" sq, screw driver inserted into the flywheel inspection hole. There are slots in the flywheel, at least for the 95-99 cars, which you can position the screwdriver. The mechanical advantage is maybe 7/1, the flywheel is about 1' radius, so it only takes 20 lb force to hold the engine rotation against the 140 ft-lb torque.
You got it backwards. 140 ft-lbs of torque is exactly 140 pounds of force applied to the end of a 1 foot lever. Your mechanical advantage is that you use a 2 foot breaker bar to turn the bolt, so you only push with 70lbs of force, 2 feet from the center of the crankshaft.
The hole in the flex plate is only about 6 inches from the center of the crankshaft (if that). 140 ft-lbs at half of a foot means the force applied to the screwdriver doubles. The screwdriver has to hold 280 lbs.
A good screwdriver is able to hold this. A cheap Chinese screwdriver may break.
Posted 16 December 2012 - 06:54 PM
You misunderstood my point. The mechanical advantage occurs by comparing the distance from the edge of the flywheel to the housing, versus the length of the screwdriver outside the housing. The overall length of the screwdriver is 12". If the distance from the flywheel to the edge of the housing is 1", and I push against the turning force 1" from the end of the screw driver, then the mechanical advantage would be 10/1.
In any case, the important point that I wanted everyone to know, is that one person can easily hold the flywheel while pushing the torque wrench at 140 ft-lb on the crank bolt with the other hand. In short, it doesn't take much strength at all.
Also, as a matter of fact, I did change crank bolt because I was afraid that the original bolt wasn't high strength. But the old and new bolt were identically marked. And finally, I have seen posts of crank bolts loosening so it must have occurred at least a few times.
Posted 16 December 2012 - 07:49 PM
Loctite (Or a good quality RTV like RightStuff)
That way even if you can't hold the crank super tight for perfect torque, the bolt will be unlikely to vibrate loose.
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