Spun Mains in 402
02-02-2007, 11:04 PM
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Spun Mains in 402 Oh well thats racing.
My machinist is saying that it was likely detonation. Is he as full of it as I think he is?
My recollection is that spun mains are nearly always an oiling issue. Cracked ring lands is a detonation sign.
The pistons look good. Also I log continually as well as use a wide band often. I am saying BS to the detonation and most likely bad oiling.
BTW, he has some skin in the game on bad oiling since he rebuilt the motor 3000 miles ago due to a cam bearing that walked. I am guessing the motor had oiling issues he missed the first time around. This is the second rebuild in 7000 miles on a new 402.
Perry
My machinist is saying that it was likely detonation. Is he as full of it as I think he is?
My recollection is that spun mains are nearly always an oiling issue. Cracked ring lands is a detonation sign.
The pistons look good. Also I log continually as well as use a wide band often. I am saying BS to the detonation and most likely bad oiling.
BTW, he has some skin in the game on bad oiling since he rebuilt the motor 3000 miles ago due to a cam bearing that walked. I am guessing the motor had oiling issues he missed the first time around. This is the second rebuild in 7000 miles on a new 402.
Perry
02-03-2007, 01:33 AM
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Never have seen detonation hurt a main bearing. Rod bearings yes, but not to the point of wiping one. You need to find a new builder...
Was the block align honed? Do you have clearance specs?
Pictures will be very helpful.
Was the block align honed? Do you have clearance specs?
Pictures will be very helpful.
02-03-2007, 06:09 AM
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Originally Posted by pkincy
Oh well thats racing.
My machinist is saying that it was likely detonation. Is he as full of it as I think he is?
My recollection is that spun mains are nearly always an oiling issue. Cracked ring lands is a detonation sign.
The pistons look good. Also I log continually as well as use a wide band often. I am saying BS to the detonation and most likely bad oiling.
BTW, he has some skin in the game on bad oiling since he rebuilt the motor 3000 miles ago due to a cam bearing that walked. I am guessing the motor had oiling issues he missed the first time around. This is the second rebuild in 7000 miles on a new 402.
Perry
My machinist is saying that it was likely detonation. Is he as full of it as I think he is?
My recollection is that spun mains are nearly always an oiling issue. Cracked ring lands is a detonation sign.
The pistons look good. Also I log continually as well as use a wide band often. I am saying BS to the detonation and most likely bad oiling.
BTW, he has some skin in the game on bad oiling since he rebuilt the motor 3000 miles ago due to a cam bearing that walked. I am guessing the motor had oiling issues he missed the first time around. This is the second rebuild in 7000 miles on a new 402.
Perry
i also agree that it sounds like an oiling problem.
02-03-2007, 07:40 AM
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Hi Folks
I have never heard of that before - I would definitely look at oil pressure and bearing clearance. If they did not have the right clearance on the main and lack of oil, the bearing will spin.
Thanks
Bill
I have never heard of that before - I would definitely look at oil pressure and bearing clearance. If they did not have the right clearance on the main and lack of oil, the bearing will spin.
Thanks
Bill
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02-05-2007, 09:05 PM
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good question. SDPC is now using Scat H beam 6.125s in their 402s but mine was one of the first ones built and I recall it was Crower at that early date (12/04-1/05)
Perry
Perry
02-05-2007, 09:28 PM
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what the hell, ive never heard of ANYONE spinning a MAIN bearing. it wasnt put together correctly IMO. either something got in the motor, the crank was messed up, bearings were messed up etc.
02-05-2007, 09:46 PM
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I just had the same thing happen to me! The pistons, rods, spark plugs and all logs looked fine. They said it was detonation, I just don't understand how?
02-06-2007, 04:04 PM
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Originally Posted by Tiger2o69
I have either spun as main or rod bearing as well. I have scat rods and stock crank. cleavite bearings.
Perry
02-06-2007, 07:06 PM
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Never seen a main spun... please post up some pics.... seems to me that it would have to be an assembly and/or oiling issue.
I spun several rod bearings last year on a stock LS2 with less than 10 hours on it due to oil starvation... the mains were galled, but far from spun
Of course, it could have been my fault cause I was using the motor for this....
I'm a firm believer in the value of an oil accumulator now. At least for what I do.
I spun several rod bearings last year on a stock LS2 with less than 10 hours on it due to oil starvation... the mains were galled, but far from spun
Of course, it could have been my fault cause I was using the motor for this....
I'm a firm believer in the value of an oil accumulator now. At least for what I do.
02-06-2007, 08:12 PM
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I would look to see if the plastic dumb bell that goes in the main oil gallery in the back of the block is there? If you put a welch plug in the back like is in the front then the oil will bypass the filter....kinda hard on mains....if you know what I mean.
Good luck Perry
Good luck Perry
02-07-2007, 01:01 AM
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Good point Brian.
And I did check that when I had the cam bearing walk last year this time.
BTW, the heads show no damage. I am having the springs checked for pressure simply because it seems a reasonable thing to do with them off the car now. I am also having them look at the valve seats but am expecting everything to be OK. I don't think I have but 10-12,000 mostly street miles on the heads.
Keep up your good work.
Perry
And I did check that when I had the cam bearing walk last year this time.
BTW, the heads show no damage. I am having the springs checked for pressure simply because it seems a reasonable thing to do with them off the car now. I am also having them look at the valve seats but am expecting everything to be OK. I don't think I have but 10-12,000 mostly street miles on the heads.
Keep up your good work.
Perry
02-07-2007, 02:31 PM
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Originally Posted by pkincy
Good point Brian.
And I did check that when I had the cam bearing walk last year this time.
BTW, the heads show no damage. I am having the springs checked for pressure simply because it seems a reasonable thing to do with them off the car now. I am also having them look at the valve seats but am expecting everything to be OK. I don't think I have but 10-12,000 mostly street miles on the heads.
Keep up your good work.
Perry
And I did check that when I had the cam bearing walk last year this time.
BTW, the heads show no damage. I am having the springs checked for pressure simply because it seems a reasonable thing to do with them off the car now. I am also having them look at the valve seats but am expecting everything to be OK. I don't think I have but 10-12,000 mostly street miles on the heads.
Keep up your good work.
Perry
