Warning keith black pistons for 340

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69340

69340

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Hi FABO members just wanted to let all know that you should make sure to check new pistons out of the box. Had my block bored and honed for new set of kb hper pistons. Machinist found 3 collapsed pistons. Had to order a new set from kb . Anybody else had this problem kb243.040.
 
I have KB,s in my motor and have no issues.It,s good your machinist found out,I,m sure they will exchange or total refund.Good Luck!
 
Ok I have to ask since I don't know. What is a collapsed piston exactly I have never heard of that. TIA Justin
 
IIRC. a collapsed piston is a piston whose skirt diameter has been reduced. Usually, due to heat other issues while in a running engine. Not sure why new pistons would be collapsed. Glad they were caught in time.
 
The Machinist told me that 3 of the skirts were between .006-.008 thousands
out compared to the other 5 ? he could not give a reason why as they were right out of the box. I couldn't even get 3 new ones as the weights of the ones in stock at kb were lighter by 28 grams. they had to send me a new set. they were good about it and i will get my money back when the others are returned.
 
So If I am understanding this correctly are you guys saying that the collapsed pistons were approx. .032-.034 over instead of being .040 like they were supposed to be. Is that right or am I getting myself mixed up. Thanks Justin
 
Yes I think you have it right, they were under sized. The skirt area is where they are measured when determining piston to cylinder wall clearance.
 
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