Here's a story I have related beefore : "Back in the early '60's, I knew a guy that ran a 270 HP dual-quad '57 Chevrolet Bel Aire 2 door hardtop in SS/C (I think that was the class). He was very successful, winning his class at the NHRA Nationals in 1961. The next year, he decided to keep ahead of the competition and installed the power train from the Bel Aire into a 150 two door sedan that was originally a 6 cylinder car. The car ran strong, but for some reason, was never quite up to the performance standards he had seen in the Bel Aire. To make a long story short, the 6 cylinder Chevrolets of that era had a 5/16" fuel line, while the eights had a 3/8" line. Replacing the line from the tank forward with the proper 3/8" line improved the performance on the sedan to a bit better than the hardtop."
Not all the V8’s had a 3/8” line only the 270’s and FI’s did. I use a Tri-5 V8 flex line from the line to the fuel pump on my 56 Ford and it’s a 5/16”; I bought it from Danchuk. It’s also a way to see if the 57 you might be looking at to buy is a fake.
Thanks for all the replies. The blueprint engine’s carb has a 5/16 fitting so I think I will do the mod that Highlander did to the tank to get 5/16 all the way.
So you can't name a downside to "GM’s one item fit’s all mentallity" that you seem to be criticizing. They did it because they tend to use like items for simplified production and therefore lower costs when it doesn't matter. 3/8" fuel line when the engine only needs 5/16" will have no downside to the operation of the engine. I much prefer that mentality to than of Ford or Chrysler where there are 27 options for the part you need depending on the vehicle configuration. No thanks. Will the OP's engine require 3/8"? Unlikely. But it's a good idea to do now with no down side, so any future upgrades don't produce any fuel starvation issues.
What criticism?, just saying it’s a 1 part fit’s all but engineered only once approach which answers your question as to why a wimpy engine gets an over sized fuel line.
You have a near identical situation as myself except that my car is a '46 Tudor. If your DRAKE tank pick-up line thread is 1/2" UNF like mine it's easy to upgrade to 3/8" lines. I bought 1/2" inverted flare to 9/16" JIC adapter and 569 Loctited it into the tank. https://www.summitracing.com/parts/rus-640330 Then I bought 9/16" JIC to 3/8" barbed adapters to allow rubber hose connections. https://www.zoro.com/parker-hydraulic-hose-fitting-916-18-jic-30682-6-6/i/G9213189/ You can also use -6 AN fittings with these adapters if you want that look. They also fit the fuel pump outlet port which provides a foundation for a 3/8" line to the carb. I ran 3/8" steel bundy tube in between the tank and fuel pump. Shop around as these fittings are readily available from most industrial suppliers.
At Ford's Dynamometer Test Operations Building, in the era of carburetors and carbureted fuel pressures, it was generally accepted that a 3/8 fuel supply line would handle an engine up to 600 HP. Of course dynos don't accelerate but you can get a ballpark feel for wheher you need to go as big as 3/8" if you are approaching the 600 HP mark.
Summit has recommendations based on horsepower level. https://help.summitracing.com/app/answers/detail/a_id/4879/~/what-size-fuel-line-do-i-need? One thing to keep in mind is that the area of the fuel line increases more than the diameter increases. For instance, a 5/16" fuel line is 1.25 times the diameter of a 1/4" fuel line, but the area is 1.6 times larger. A 3/8" fuel line is 1.2 times the diameter of a 5/16" fuel line, but the area is 1.43 times larger. Going up in diameter gives you a larger increase in area, which over the length of the line translates to a larger volume of fuel the line can hold and therefore is quickly available to your engine. As long as your pump can handle it, in general a larger line is better.
I've got about a foot of 1/4" rubber on mine, from the tank to the inline filter then to the electric pump, then 5/16" ni-cop from the pump to the flex line which is -6 or 3/8" to the carb. With the stock 302, I've never had delivery problems, but then again I'm not racing it, either.
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