AN816 nipple - which one

Hi,
I want to link two fuel lines with a JPI 201B Fuel-Flow Transducer. The Transducer has the connection "1/4 Female NPT (H) AN816-8-8" (0.54 inch) and the Fuel line has a flared tube with 0.56 inch outer dimension.

Which AN816 do I need to connect Line and transducer ?

Thank you, Achim

That blue fitting your measuring is a male -6 AN. That is typically used with 3/8" fuel lines. Sounds like you need a 816 with -6 on one side and 1/4" NPT on the other.

Which model transducer did you buy? The 201, 231, or the H? Is that black fitting the transducer?

From the website:
Range (201) 0.6 to 60 GPH, (231) 3 to 90 GPH, (H) 3 to 120 GPH
Fuel ports (201, 231) 1/4 Female NPT (H) AN816-8-8

It looks like the H comes with an -8AN fitting, which won't fit your fuel lines. That blue fitting is an AN6 and fits 3/8 fuel lines. To adapt the 1/4NPT ports to 6AN you'll need 2 of these(one for inlet and one for outlet):

https://www.summitracing.com/parts/sum-220647b

If you want to bolt the transucer directly to the blue fitting you can do so with one of these:

https://www.summitracing.com/parts/sum-220641b

It would be better for vibration if you didn't mount directly to that port and instead put it inline with the fuel tubing somewhere it can have support. In that case, you'll need to cut a section out of the fuel line and install these ends on each line with a 37 degree flare tool(so 2 total):

https://www.amazon.com/Female-Aluminum-Hardline-Fitting-Adapters/dp/B07QFGKBCT

AN816-8-8 is -8AN to 1/2 NPT male. Obviously not going in a 1/4 NPT port on the transducer. IF you have a -6 hose, use a AN816-6D.
Tom