Fuel Line - Filter

[Dave O]

On my C&C 29 I have a 1/4" fuel hose leading from the tank to a Racor filter, and 1/4" hose leading from that filter to the carb. I'm installing Don's polishing filter and I notice the fuel hose size supplied is 5/16".

1. Any problems mixing the sizes ... 1/4" to the Racor filter and then 5/16" after? Or would it be better to change everything out to 5/16"? The Racor fitting are 1/4" - 18NPFT but 5/16" fuel hose fits very tight.

2. Also, the Racor instructions read ... "Do Not Use Teflon tape on NPT threads". Any idea why? Or what pipe sealant to use?

[jayw]

I don't think mixing the 1/4 and 5/16-inch hose sizes would be a problem for fuel flow.
As for the teflon thread tape, I don't know the correct answer but when I used teflon tape on another fuel filter, I cracked the housing where the hose barb screwed in by overtightening. The teflon makes overtightening easy to accomplish.

[Don Moyer]

There is no particular reason why you couldn't use a bit of 1/4" hose in the same system with 5/16"; however, we consider 1/4" a bit small for runs over 2 or 3 feet.

I'm not sure why Racor technical folks discourage the use of Teflon tape for fittings, but the reason we discourage it is because we find small tidbits of Teflon tape in carburetors and fuel pumps now and then. We prefer almost any paste sealer to Teflon tape on fittings. Permatex Aviation Brand sealer works well and also any of the Teflon paste products available at most auto parts stores.

Don