[lust4speed]

I would expect to see the rear edge of #5 bearing tore up if the problem was the radius contacting the bearing. Instead it looks like either the block bearing journal was machined smaller at the rear or the bearing was thicker at the rear. Possibly the guy running the hone was pulling up short or there was another problem? The journal size can still be measured to rule this out. Also, a short radius touching the bearing would attempt to spread the bearing and damage would be much more centralized at the rear. I use Clevite bearings because the FM Babbitt thickness's were all over the map while the Clevite's were much more uniform, but...

How did #4 thrust spin 1/2" or so and the tangs are still perfect?

Don't think we will ever figure out the plugs closing up or the chipped cam gear.

Just think we're going down the wrong rabbit hole chasing the position of the rear bearing.

[MarkS57]

Originally Posted by lust4speed

I would expect to see the rear edge of #5 bearing tore up if the problem was the radius contacting the bearing. Instead it looks like either the block bearing journal was machined smaller at the rear or the bearing was thicker at the rear. Possibly the guy running the hone was pulling up short or there was another problem? The journal size can still be measured to rule this out.

This is a good point. Something noticed in post 193 (attached) check out the red circle.

[mgarblik]

Been thinking about the Butler response to this condition being core shift and that being dismissed out of hand by everyone in the thread. While I agree a machining error in tang location or the crankshaft is the most likely cause, IMO core shift is a possibility. Here is how. The main saddles are part of the multiple cores assembled in the core box for the block. During the pour of there was a minor shift in the core box, one or more of the main saddles could be slightly out of position. When it was originally line bored and assembled with a cast OE crankshaft with almost no fillet radius it may have just barely cleared and run without issue. When the Scat crank was installed with the large radius, everything changed as far as fitment and minimum clearance and then the failure. So , I am saying core shift is possible. It's something I have never seen in the #5 of a Pontiac, but I learn new things every day. I will sure be looking more carefully in that area now.

[wbnapier]

mgarblik - Maybe.

For me, I am trusting the machinist on this. He told me that he is sure, with certainty, that it is a #5 Clevite bearing issue. He has compared it older style Clevite bearings and modern FM bearings. He has bearings there now, 3", 3.25", standard and 10 under. Also, he has the Clevite rep involved, whom respects his diagnostic abilities enough to come to the shop and now has scheduled a revisit to pursue this as a QC issue.

Also, I want everyone to know that is reading this, that my only request of Butler was to contact Clevite, as a reseller, on my behalf regarding the QC issue. I told them that the local Clevite rep is involved and gave them the contact info of my machinist.

It would be great, if out of this debalcle, Clevite would introduce a more chamferred and/or narrow bearing for aftermarket forged crankshafts.

[mgarblik]

I agree with you. It's great that a Clevite rep is interested enough to get involved. It is also in their best interest to determine if it is in fact a bearing problem so they can recall effected bearing sets, or at least get the word out to vendors, shops and customers to check for a defect if one is found. Not doubting your machinist at all. If Joe Sherman was involved with this shop I would trust them absolutely.