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Discussion Starter #1
Hi guys,
Long story short, I had a small oil pan leak..... couldn't help myself and pulled a couple caps on the mains apart just to be sure. I was shocked to find a bunch of things i had never seen. Well first main cap i pulled off the bearing looks horrible, crank is good and all the rest of the bearings while not perfect are in much better shape. I have attached pictures of what i have torn apart so far.
I also attached pics of the main caps and saddles, it appears that there is cap walk? Stock bolts at 105lbs.
This thing is 13.1 compression and we ran it on 93 octane on the dyno. :oops: I know, i know, I had specified 10.7 to 1 and apparently the guy who built the motor was not listening when i said pump gas friendly. It detonated on the dyno which lead me to tear down the top end and discover flat tops with my iron cobra jet heads. I plan to leave it alone and just run a good race gas but need to get the main bearing issue taken care of and put back together. I'm wondering if there was a small burr on the oil hole in the crank or a burr on the alignment tab on the bearing itself??? It smeared itself into itself. No other bearing looks this way. To the naked eye, i couldn't see anything in the oil. We were running Driven 15-40 full synthetic for the pulls and Brad Penn break in oil for the first hour for cam break in. Total run time on engine would be estimated to be about 5 hours or so.
I have attached a pic with the plasti gauge at .002. I haven't pulled the pump off yet so I have done cap 1 but all 4 so far are sitting at .002. Should I replace them all, just the bad one??
Thank you
 

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Given the circumstances you'd better check the rod bearing as well.
Detonation of the type you would have experience can place severe stresses on the bottom end causing main cap flex as well as hammering the top rod bearing to death.

Imo replace them all.

A fleck of crap could cause the scratch mark shown. If not embedded in the bearing it was likely flushed out and caught in the filter. Some times no matter how diligent you are during assembly a stray piece of something comes loose. It's maddening sometimes.

With mild cap walk in some of our higher powered stroker combos I leave the fretting alone. The OEM bolts have a shoulder that fits the cap better than the ARP bolts. I know it sounds counter intuitive.


SJ
used 2b RHP
 

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Discussion Starter #3
Thanks scott,
I'm going to check end play before it is torn down just to verify. what are your thoughts on the radius of the crank polishing off the edges of the bearing in the pic?
 

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Stroker cranks need a narrower bearing. Clevite H series is what we use for the most part. Looks like your bearings are not suitable for the larger radius.

SJ
used 2b RHP
 
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