427 truck block oil pressure fitting

[engineman1642]

I have a customer who has a 427 chevy truck block ,sez fitting above oil filter is neither 1/4 or 3/8 pipe.Anyone know what it might be? thanks

[machinedave]

I have one in the shop now. I just checked it and it is 3/8" pipe.

[SupStk]

+1
Also have one here and its 3/8 pipe.

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[Newold1]

The 427 tall deck truck block I have in my shop is also a 3/8"npt size threaded hole above the oil filter pad as shown above.
someone may have taped it out to a larger size like a 1/2" pipe or #10AN size. Seen this done many times for a remote oil filter or cooler setup.

[engineman1642]

have not seen the block ,but he said that 1/4 " fitting falls into thread and 3/8" is way bigger than the thread in block.

[SupStk]

Guess I've never seen the oil port above the filter in a BBC that wasn't at least 3/8 NPT. There are blocks that are even bigger but not in truck engines, from what I've seen.
Wonder if there is something, such as a reducer, adaptor or some other fitting screwed in the hole?

[gramps]

Had same deal SBC bowtie block lower water drains, ended up being 9/16-18 thread or AN6 plug.

[pamotorman]

I have gotten used SBC blocks with 3/8 NTP plugs in the water jacket drains. most like the original 1/4 NTP threads were stripped,distroyed or rusted out.