Working on a 57 Plymouth 301 poly motor. I'm familiar with the newer 318's, 340's, & 360's that use an expansion plug in the oil galley under the rear main cap to keep unfiltered oil from mixing with filtered oil, but this 301 did not have an expansion plug and appears not to be machined to accept an expansion plug. The block has a restricted passage between the unfiltered and filtered oil passages with an approximate .100" hole in it. Did they allow a small amount of oil to go through the .100" hole unfiltered?
Thanks, any help would be appreciated.
hjc

 

Don't know myself, found this.

http://www.forwardlook.net/forums/fo....asp?tid=46392

 

Thanks for this information. This block most likely had the same type of valve setup. Unfortunately, I sent it through the cleaner and didn't notice it. If you know of any source of antique parts like this, please let me know.
hjc

 

I quickly read that if it's converted to a modern oil filter it will have an internal drain back and that part is not needed.