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glennpm · 11-04-2020, 02:51 PM

This made me curious on the real differences between using 1/4" or 3/8"NPT fittings.

ID for 1/4" = .36
ID for 3/8" = .42 (same as flathead oil system

root diameter of 1/4" is about .48 at end of taper, so not real safe to drill out to .42. .40 would be okay.

The other thing to consider is that if using 1/4"NPT fittings, the velocity and pressure drop for the 2 effective fitting's length would have a very small effect upon the flathead oil system and large diameter oil lines to the external filter.

Glenn

11-04-2020, 02:51 PM	#17
glennpm Senior Member Join Date: Sep 2014 Location: Wiscasset, Maine Posts: 1,981	Re: Remote oil filter fitting re size This made me curious on the real differences between using 1/4" or 3/8"NPT fittings. ID for 1/4" = .36 ID for 3/8" = .42 (same as flathead oil system root diameter of 1/4" is about .48 at end of taper, so not real safe to drill out to .42. .40 would be okay. The other thing to consider is that if using 1/4"NPT fittings, the velocity and pressure drop for the 2 effective fitting's length would have a very small effect upon the flathead oil system and large diameter oil lines to the external filter. Glenn Last edited by glennpm; 11-04-2020 at 04:56 PM.