Crank thrust surfaces...swirl marks on Scat crank

Goin' to the machine shop today. Got all my stuff in the truck.

The thrust surfaces of the Scat 9000 crank have me concerned. Outward spiraling swirl marks from the manufacturer. It's smooth to the touch (polished some already), but still there just the same. If you read Clevite's catalog, they say the marks must be polished out, because they tend to wipe the oil out of the gap between the thrust surface and the bearing. I plan to tell the machinist to polish it out. I read somewhere about Scat thrust surfaces being of some controversy.

Am I over-reacting or am I on track?
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Since both machine work and crankshafts are more expensive than a phone call or email, I suggest Cranktech@ScatEnterprises.com or 310 370 5501. Not try to be a smart a$$, and I certainly think that getting an independent opinion as you are doing here is worthwhile, but Scat might tell you up front that it is a defect and save you a lot of trouble. If they tell you it is nothing to worry about, you are in the same place you are now: thinking it is a bad thing and trying to find out the truth. Only good things can come from the call, so I would call them first.

Personally, I have never heard of any bearing surface in an engine being anything other than absolutely smooth and mark free. While obviously there are some differences between a thrust bearing surface and those for mains or rods, it is still a plain journal bearing and should conform to the same rules.

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Rich
www.v8mongrel.com

<font size=-1>[ This Message was edited by: V8Mongrel on 12/1/06 2:10am ]</font>

Thats a tough call. I do know that my father's 331" Eagle cast crank suffered a thrust failure recently, for what reason, we do not know. Everything looks great except the thrust (and the #1 rod &amp; piston which broke as well as teh block &amp; cam). Torque converter is fine, trans had plenty of end play, etc. Been running the exact same combo for years and years and this is the very first 302 thrust failure I've ever dealt with, so I'm bumfuzzled. I did have one go south on a 393 a few years ago, but I believe that was my own fault (PG to SBF adapter that wasn't quite right).

I would have them polish it up as best they can. Most, if not all of the Clevite thrust bearings I've messed with in the last, oh, 2-3 years, were tight and needed some sanding on the thrust edges....so removing a little to polish the crank is probably just fine. Besides, I'd rather it be a little loose than too tight when it comes to thrust. But, 1/2" of end play is too much (which was the case in dad's 331). It was assembled at .006.
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