A26B
08-05-2008, 03:35 PM
ADVISORY, Pertaining only to 90~92 375 Hp LT5 engines:
Background: A couple of years ago, I tore down several 375 Hp engines which were part of the lot of 29 used 375 Hp engines I acquired that originally came out of GM storage about 2004. During inspection of rod bearings, some bearing wear matched the "cavitation" pattern. Due to the proven reliability of the LT5, I noted the findings but could never understand the wear pattern until now.
During "reverse engineering of gaskets & seals utilizing GM engine drawings & actual engine parts, I found that the OEM o-ring #10106189 used for the oil pump suction tube in the 375Hp engine did not meet the industry design spec calling for 25~30% compression when the oil pan was installed with the OEM pan gasket, only compressing the o-ring about 3%.
Recalling the design problems of the LT5 pertaining to crankcase windage & pressure, coupled with the oil suction tube o-ring findings, the bearing cavitation wear pattern began to make some sense. I believe crankcase vapor (air) was getting into the suction of the oil pump.
Now, I'm not being "chicken-little" and advocating the sky is falling. I do however advocate that a different o-ring than OEM #10106189 be used when the oil pan is removed. I also recommend that if a pan gasket other than OEM is used, that one should thoroughly investigate whether it meets the same standard of compressed thickness of the OEM gasket when installed. I know for a fact that there are aftermarket pan gaskets presently offered for sale that do NOT meet that criteria. If the gasket is too thick when installed, it will make the cavitation problem worse when used in conjunction with the OEM oil pump suction tube o-ring #10106189.
The pan gasket I sell, compresses to the same thickness of the OEM gasket and is made from very high quality material. The oil pump suction tube seal (o-ring) that I sell under PN 10106189, has a larger cross section diameter than the OEM part. I know that it will compress to o-ring design spec with the OEM or my pan gasket.
If you are removing the oil pan, please use the correct gasket and corresponding oil pump suction tube seal (o-ring) to insure proper sealing. Obviously the OEM parts work very well, but there have been main/rod bearing failures. I am not recommending that anyone remove the pan to install a different gasket or o-ring. However, if you do have the pan off, consider my findings in you decision for the replacement gasket & seal.
Jerry
Background: A couple of years ago, I tore down several 375 Hp engines which were part of the lot of 29 used 375 Hp engines I acquired that originally came out of GM storage about 2004. During inspection of rod bearings, some bearing wear matched the "cavitation" pattern. Due to the proven reliability of the LT5, I noted the findings but could never understand the wear pattern until now.
During "reverse engineering of gaskets & seals utilizing GM engine drawings & actual engine parts, I found that the OEM o-ring #10106189 used for the oil pump suction tube in the 375Hp engine did not meet the industry design spec calling for 25~30% compression when the oil pan was installed with the OEM pan gasket, only compressing the o-ring about 3%.
Recalling the design problems of the LT5 pertaining to crankcase windage & pressure, coupled with the oil suction tube o-ring findings, the bearing cavitation wear pattern began to make some sense. I believe crankcase vapor (air) was getting into the suction of the oil pump.
Now, I'm not being "chicken-little" and advocating the sky is falling. I do however advocate that a different o-ring than OEM #10106189 be used when the oil pan is removed. I also recommend that if a pan gasket other than OEM is used, that one should thoroughly investigate whether it meets the same standard of compressed thickness of the OEM gasket when installed. I know for a fact that there are aftermarket pan gaskets presently offered for sale that do NOT meet that criteria. If the gasket is too thick when installed, it will make the cavitation problem worse when used in conjunction with the OEM oil pump suction tube o-ring #10106189.
The pan gasket I sell, compresses to the same thickness of the OEM gasket and is made from very high quality material. The oil pump suction tube seal (o-ring) that I sell under PN 10106189, has a larger cross section diameter than the OEM part. I know that it will compress to o-ring design spec with the OEM or my pan gasket.
If you are removing the oil pan, please use the correct gasket and corresponding oil pump suction tube seal (o-ring) to insure proper sealing. Obviously the OEM parts work very well, but there have been main/rod bearing failures. I am not recommending that anyone remove the pan to install a different gasket or o-ring. However, if you do have the pan off, consider my findings in you decision for the replacement gasket & seal.
Jerry