It would be nice to know the year of your 261. If it is 1958-1962 you 'could' have a full flow system. If it's older, then it's bypass unless it has been specially machined. Very likely like Dave says its a Bypass system.

Lots of information about your engine here:

http://devestechnet.com/Home/TheVenerable261

I just added something I was very fortunate to stumble on. How long is the dowel pin that is pushed in to switch from bypass to full flow on the 1958-62 models? 1-5/8" woohoo!

Last edited by Deve; 08/25/2015 3:05 AM.
Deve

1950 Chevy 3100 Deluxe Cab
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