broken crank!
#1
Newbie
Thread Starter
broken crank!
so cruising down the street oing from 4th to 5th. i press the clutct pedal and really weird knocking/ vibrating noise comes out. pull over and check it. it seemed like tranny. go ack on the highway to go home and sounded like a clutch, get home now it sound like a motor, we pull the tranny out and inspect it and it seems fine clutch seems fine. pull the pan and come to find this. what would cause it, wasnt reving it or anything just cruising. its a 2.4 100mm crank. its from the clutch side.
#4
EvoM Guru
iTrader: (7)
It looks like a torsional fatigue stress fracture originating at the root of the radius between pin and web. It was caused by torsional vibration, and probably started at a stress concentration caused by a piece of slag, or a forging defect, right at the surface of the pin where it meets the web. Unfortunately this happens in the life of Evo!
Time for a rebuild. What are you going for next?
Time for a rebuild. What are you going for next?
#5
Newbie
Thread Starter
Surprisingly the journal was unharmed. The engine is about 6 month old. The rods were unharmed. So I got a new Manley forged crank and a new set of acl bearings. Gonna send the crank with clutch and it's component's to get balanced togethe . I am keeping the same setup since it didn't harm anything. And go back and shoot for more power.
#7
Evolved Member
iTrader: (18)
ive always heard the 4g64 OEM cranks were about 1/2 as strong as the 4G63 cranks.
You got to think... those 4G64 cranks were all in sedans... and in general, slow cars.
The 4G63 cranks were in evo's, which meant the engineers payed a little more attention to the crank strength.
You got to think... those 4G64 cranks were all in sedans... and in general, slow cars.
The 4G63 cranks were in evo's, which meant the engineers payed a little more attention to the crank strength.
Trending Topics
#10
EvoM Guru
iTrader: (7)
#12
Newbie
Thread Starter
#13
Newbie
Thread Starter
Dynamically balancing the crank with flywheel and clutch only addresses part of the problem - primary balance. I'm guessing you were running the 4g64 crank without the balance shafts right? If so, consider using a fluidampr crankshaft pulley (http://www.fluidampr.com/product/610701/) in the rebuild to reduce harmonic torsional vibrations that will rapidly fatigue the journal/web next to the flywheel.