997 3.8l Crank Repair Advice Needed
03-31-2020, 09:27 PM
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997 3.8l Crank Repair Advice Needed
Hello Folks...I have a 2006 911 4s 3.8L that had (has) a spun bearing on one journal. I had the engine disassembled and the bad journal welded and grounded. The crank was magnafluxed for potential cracks and hardened after the journal was ground down as recommended. Now I am left with a choice as to buy the oversized .10 over rod bearings and grind all the journals down or just put the stock bearings back in. My measurements on each journal with micrometer are below.
52.98 (the welded journal)
52.96
52-96
52.95
52-96
52.95
Based on these numbers I have had differing opinions on weather I should buy the stock bearings and run those as is or buy the .10 over bearings from Vertex Auto and have my crank ground down and use the .10 overs. My mechanic says I should grind the crank to the .10 over and then buy the bearings and go that route. Another engine builder told me the tolerances I posted above are probably not going to cause a problem because the tolerances are not that far off(even though the .95 is a bit under tolerance recommended by Porsche), but just to mix and match the new Porsche stock bearings as they will have + or - tolerances of their own, not to mention the variations in rod itself. The same engine guy tells me that even if I have the crank ground down .10 over there will be tolerances to deal with there as well and it will never be 100% spot on. Maybe they will be similar tolerances to the ones I already have and therefore a pointless to spend the extra money. Just wanted to get some input as to some more experienced members here. Thank you in advance.
52.98 (the welded journal)
52.96
52-96
52.95
52-96
52.95
Based on these numbers I have had differing opinions on weather I should buy the stock bearings and run those as is or buy the .10 over bearings from Vertex Auto and have my crank ground down and use the .10 overs. My mechanic says I should grind the crank to the .10 over and then buy the bearings and go that route. Another engine builder told me the tolerances I posted above are probably not going to cause a problem because the tolerances are not that far off(even though the .95 is a bit under tolerance recommended by Porsche), but just to mix and match the new Porsche stock bearings as they will have + or - tolerances of their own, not to mention the variations in rod itself. The same engine guy tells me that even if I have the crank ground down .10 over there will be tolerances to deal with there as well and it will never be 100% spot on. Maybe they will be similar tolerances to the ones I already have and therefore a pointless to spend the extra money. Just wanted to get some input as to some more experienced members here. Thank you in advance.
