Dual Feed Fuel Line Setup

I'll take your word for that and avoid them.
Last one I bought was a Mr Gasket. It was typical steel fuel line with chrome plating but nothing to write home about.
The flares weren't finished well and of course it was made you know where.

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Comapre that to this used late 80s Holley non-chromed.
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My suggestion for the OP was not to have a any soft line between the two bowls. Not braided, not anything. Less chance of leaks.

That flare IS finished. You know why it's concave like that, instead of flat like it's supposed to be? Because the material it's made from is TOO THIN to take a double flare and mashes all to hell instead of finishing correctly. Yeah, I strongly suggest staying away from the Holley parts now. ......and mine was a bonafide Holley branded part. It's still on there, but I'm probably going to do something different before it fires up.