Oil Filter-ology

[Don T]

This is just for information; my 2 CDN 8Ba's with factory filter do not have a restriction on the inlet to the filter; the restriction is downstream of the filter. The restriction is a very small hole drilled in the center shaft which is the return "pipe" to the pan. I guess this would mean the filter would clean the oil before it had a chance to plug the restriction which would not be the case with the restrictor on the inlet. I doubt if the filter would drain down 1/2 a pint when sitting for a long time in which case I would guess the filter itself would act as a restrictor on start-up. Both of these engines had the restrictor hole plugged (with crud) when taken apart, effectively the filter would never get dirty so unlikely it was ever changed. Restriction plugged= no filtering.

[51 MERC-CT]

Originally Posted by Don T

This is just for information; my 2 CDN 8Ba's with factory filter do not have a restriction on the inlet to the filter; the restriction is downstream of the filter. The restriction is a very small hole drilled in the center shaft which is the return "pipe" to the pan. I guess this would mean the filter would clean the oil before it had a chance to plug the restriction which would not be the case with the restrictor on the inlet. I doubt if the filter would drain down 1/2 a pint when sitting for a long time in which case I would guess the filter itself would act as a restrictor on start-up. Both of these engines had the restrictor hole plugged (with crud) when taken apart, effectively the filter would never get dirty so unlikely it was ever changed. Restriction plugged= no filtering.

US filters have two (2) holes in the center return pipe at the same level as the restricted inlet.
There is no restrictor hole in the inlet to the filter. The restrictor hole is in the fitting that goes into the inlet hole on the filter.