Re: The source of the knock

[bearbvd@domain.elided (Greg Hermann)]

At 6:54 PM 1/13/03, TJ Noto wrote:

Or, quite possibly some source of detonation in the #3 cylinder, such as a
vacuum leak. (Possible bad booty between the carby and the manifold.)
Detonation could easily hammer the piston, its rings, AND the rod bearing.
Detonation can easily hammer a rod bearing in the manner you describe.

Have you checked the side clearance on the rings for #3 piston ?? Are the
#3 ring lands all even still there??

The _FIRST_ knock may not have eminated from the rod bearing !! :-)

Greg

>Tonight I pulled the big end-cap off the number 3 con-rod and was not
>surprised to find that the bearing was wasted.  If you recall, the
>engine in Shakespeare had a telltale knock on acceleration.  To me, it
>had the unmistakable sound of a rod bearing.  A compression check showed
>lower compression in the #3 cylinder, I'm not sure how a rod bearing
>failure would lead to that, maybe it's coincidental, but I figured that
>the #3 rod bearing would be bad.  The cause of the failure appears to be
>either oil starvation or improper assembly.  It overheated at one point
>and warped the bearing shell to the point that it does not even fit in
>the rod-cap properly.
>
>This crank appears to have been ground 030 under based on the numbers
>stamped on the bearings (conrod).  Does anyone know what the limits are
>for a 1600cc crank?  The otherwise pristine crank is in need of a
>regrind on that journal so the whole thing will need to be reground.  I
>don't think polishing it will clean it up enough.  I'd really like to
>not have to get another crank.
>
>I'm still in the process of taking the crank out and the rest of the
>components apart, so I'll look for the cause of the failure on this
>bearing.
>
>I'll post a picture of the bearing on the website sometime tonight.
>
>Regards,
>TJ
>
>TJ Noto         AFM #134        Cowpoke Racing-"Friends in Slow Places"
>http://www.cowpokeracing.com
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