Question on flared fuel lines

Soon I will be running the fuel line on my car, 48 chevy stock fuel tank to mechanical holley pump and then from pump to the carb. I was going to flare my own lines with 5/16''. Is it the same kind of double flare as you do with brake lines? I also want to find some kind of inline filter for under the car that accepts the flared line. Does this sound like a plan? I dont want to use any rubber under the car if possible but I will use 3/8'' braided stainless rubber jst from the mechanical pump to the fuel rail on the carb. Thanks

 

The double flare technique is the same as for brake lines. If you can find a threaded fitting filter, that's great....I understand about not wanting to run rubber line, I've had a couple of the metal inline filters leak when the 2" long rubber hose connecting them to the metal line got old and cracked.

beware the EFI filter for GM cars, with threaded fittings, are for a bubble flare that's sealed with an O ring. Not a normal inverted flare.

 

Thanks for the info!

 

im no expert, you may want to confirm but i would think a single flare would be fine. the fuel line has fairly low pressure in it where the brakes are 1200 psi but im sure someone will chime in here

 

double flare...it's not the pressure, it's the cracked end of the tubing that is why you need a double flare. And it seals better also, having two layers

 

Ditto.

 

Double on the double. It's not just for the burger joint.

 

I single flare them but use an AN fitting, tube sleeve and nut. Have yet to have a problem in 30 years. Just another choice in how to do it.

 

If you going to run the flare into a filter then double flare. You can get one with female pipe threads and put on br*** inverted flare ends, but most are non see through, like squirrel said stay away from stock GM filters....wrong type of fitting. If your going to use rubber line to the filter, just use the double flare tool and make a slight bubble or bump in the line, just enough for the clamp to stay on (ever try to get a fuel hose over an inverted flare).

 

You can buy a "fuel line repair kit" from the parts stores that has the fittings for an in-line metal cannister filter as used on GM trucks with throttle body injection. These run about the same fuel PSI as a carb motor, so it should work okay. The fittings have a rubber O-ring on them. A couple fittings and you can flare the ends and it will probably be okay. I say probably because depending on how you store the car you may have trouble down the road changing the filter; my late model beater the factory union at the firewall came right apart, but the fittings at the fuel line were frozen right up.

So when I put one in now I put a piece of rubber fuel line hose at each end; worst case I can cut it away and replace it and not destroy the lines into the filter.

 

It's actually a flat disc formed in the tube, kinda like a bubble flare where the 'bubble' is flattened all the way. The Mastercool hydraulic flaring tool, for one, will do those flares. Those GM filters are a nice piece and not too bulky. They take a 3/8in line (which in the non-HAMB-compliant 43psi EFI world is good for 600HP or so). They need a tube nut with a flat end; I bought a bag of the tube nuts on eBay I think. GM used those filters in everything from TBI pickups (which run not-much-over-carb fuel system pressures) to ZR1 'Vettes.

Long time ago I used to use the little metal inline filters that were intended for the Rochester mechanical FI, IIRC they were a 5/16 inlet with an SAE flare (or was it a pipe thread?) on each side.

 

As for filters, I like to use a fuel inj. filter on all builds. For non-HP engines, I put an 86 BMW 325 filter down on the ch***is. 5/16" barb fittings, so you can use hose on it, and it filters out the really fine **** that can still clog up a carb. AND it's capacity is much higher than a tiny carb-type filter.