CT525 piston part #? Robin please help.
06-27-2010, 01:49 PM
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CT525 piston part #? Robin please help. We had 2 hours on the engine and blew a piston (#2) on a new CT525 and am not sure if it was faulty or our fault. AFR at 12.5-1, 5800 rpm, timing @ 31, density altitude @ 2800 ft, fuel 50/50 mix of Av gas @ 104 octane and Premium fuel @ 91 octane.
It looks like the top edge of the piston broke off down to the first and second ring lands with some minor scoring which cleaned up ok. The cylinder walls have no cross hatch pattern left on them and are now wore .001 in +/- which we're told is how they are designed?? Engine was broke in as per CT525 installation manual except we used conventional Esso 5w30 with a bottle of GM EOS instead of only Mobil 1 5w30. All the other pistons look perfect except for #8 has some minor scoring which can't even be felt with your finger nail or a dental pick. The spark plugs also look good except for #2 which is burned off. The top ring end gap on #2 piston measured .014 in and .022 in. on the 2nd ring.
The CT525 manual says the piston part # is 19207287 and the GMPP catalogue says 19168089?? Also, I think its probably a misprint but the GMPP catalogue says the bore on the CT525 is 4.065 and all the LS376 engines are 4.06??
We're also looosing oil pressure down to about 20 psi @5800 rpm (Mobil 1 50/50 mix of 5w30 and 5w50) oil temp @ 260 F)on hard right hand corners even with a 2 qt accusump. We would prefer not to have to brake the seal on the oil pan and replace it with a better pan as we're trying to promote a "Sealed engine" class.
Also, as we're part of the organising group for this new class, we would like to know how the seals work/designed on the CT525 engines so we know what to look for if they're tampered with?
Thanks in advance.
It looks like the top edge of the piston broke off down to the first and second ring lands with some minor scoring which cleaned up ok. The cylinder walls have no cross hatch pattern left on them and are now wore .001 in +/- which we're told is how they are designed?? Engine was broke in as per CT525 installation manual except we used conventional Esso 5w30 with a bottle of GM EOS instead of only Mobil 1 5w30. All the other pistons look perfect except for #8 has some minor scoring which can't even be felt with your finger nail or a dental pick. The spark plugs also look good except for #2 which is burned off. The top ring end gap on #2 piston measured .014 in and .022 in. on the 2nd ring.
The CT525 manual says the piston part # is 19207287 and the GMPP catalogue says 19168089?? Also, I think its probably a misprint but the GMPP catalogue says the bore on the CT525 is 4.065 and all the LS376 engines are 4.06??
We're also looosing oil pressure down to about 20 psi @5800 rpm (Mobil 1 50/50 mix of 5w30 and 5w50) oil temp @ 260 F)on hard right hand corners even with a 2 qt accusump. We would prefer not to have to brake the seal on the oil pan and replace it with a better pan as we're trying to promote a "Sealed engine" class.
Also, as we're part of the organising group for this new class, we would like to know how the seals work/designed on the CT525 engines so we know what to look for if they're tampered with?
Thanks in advance.
