Are 1mm over rod bearings acceptable for 300 whp?
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Are 1mm over rod bearings acceptable for 300 whp?
I’m looking for 1mm over rod bearings or else I’ve got scrap my crank. Has anyone had experience with 1mm over bearings? I didn’t think it would be a huge issue machining it down that much, but does anyone with more knowledge have any opinions? My machinist seems ok with 1mm over bearings with my power goals of < 300 wheel horsepower. The bearings in question are the CR4105AM10 King AM series bearings. They’re available from summit racing I believe. It would be mixed duty driving some track duty but 90% street. I wanted the XP series bearings but they’re not available 1mm over so that’s how I’ve arrived at these bearings. Any thoughts or opinions would be very appreciated.
#4
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Yeah, makes me wonder if you or your machinist transcribed the units incorrect. Typical crank grinds start at .25mm, or .010", then step to .50mm or .020". After that I'd scrap the crank, I had no idea larger oversized bearings even existed.
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#7
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Why do you want XP bearings? Despite my due diligence, I had nothing but problems on a few sets of ACL Race bearings, and one set of the King XPs. Just excessive metals in the oil analysis, that was confirmed with multiple tear downs. I finally put OEM rod and Mahle OE equivalent mains in, and oil analysis have never looked better.
But regardless, I don't know anyone that would recommend grinding 1mm oversized.
But regardless, I don't know anyone that would recommend grinding 1mm oversized.
#8
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Why do you want XP bearings? Despite my due diligence, I had nothing but problems on a few sets of ACL Race bearings, and one set of the King XPs. Just excessive metals in the oil analysis, that was confirmed with multiple tear downs. I finally put OEM rod and Mahle OE equivalent mains in, and oil analysis have never looked better.
But regardless, I don't know anyone that would recommend grinding 1mm oversized.
But regardless, I don't know anyone that would recommend grinding 1mm oversized.
I know 1mm grind is relatively a lot, but why would they make bearings in this size if it weren’t ok? Also if .5mm grind is perfectly acceptable, what’s another .5mm realistically going to do? It’s not like I’m shooting for the most ambitious power goals. Are there any proven problems grinding it down this far or is it that it just isn’t common. People make 500+ wheel HP on the stock crank. I don’t think 1mm off is gonna cause problems at like 280 whp. In terms of area of the circle its only a difference of 4.4%
Unless there’s true empirical evidence as to why 1mm won’t work, I’m thinking the AM series rod bearings and OEM everything else. If it blows up I’ll buy you a beer and admit you were right lol
Last edited by Watterson02; 04-06-2022 at 01:19 PM.
#10
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anyways I’ve messaged curly and another member looking into buying a crank off of one of them. Ill probably give the machine shop a call today and let him know not to start working on that crank. That probably concludes this thread. OEM .25mm or .50mm bearings here I come lol
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