mr. S said:Found this while installing new springs on my 55 the other day. Looks like it got partially crushed by a lift at some point. Think it could have caused fuel delivery issues, or not so much?
it's 5/16" metal fuel line, I would think still enough for a 400hp 350.It looks like the line was squished by careless lift pad placement at some time in the past
The cross sectional area of a typical 5/16" fuel line, will allow the typical chevy manual fuel pump too fill a carburetors fuel bowls just fine under general driving conditions,
but if you put the gas petal to the floor, and hold it there for several seconds , it will have a hard time maintaining the full fuel level, thus under full throttle, the cars likely to run ok through first and maybe second gear then fall on its face, or develop what feels like a bad ignition miss, as the fuel bowls level drops and the fuel flow can,t keep up with demand,
many guys will think its an ignition related issue , or maybe "VALVE FLOAT" as it kicks in only as the engine rpm levels exceed about 5000 rpm plus , or blame the intermittent miss on valve float, but the truth is your suddenly running very lean and it cures itself once the demand drops off as you let the rpms fall back into the range where the fuel pump and line restriction allow enough fuel to flow to refill the carbs fuel bowls.
if your building a serious performance fuel system on a street car Id suggest you look at this diagram and carefully read the links posted below.
fuel line size does mater, and just installing a performance fuel pump rated at 80 GPH-to- 130 GPH, will generally help but certainly won,t cure every fuel starvation issue, that the typical stock 45-60 GPH manual fuel pump may be contributing too.
https://www.summitracing.com/parts/anm-cp7838
and rev the engine a few times and watch the fuel pressure it should in theory remain in the 38 psi-42 psi range for most TPI and TUNED PORT efi
If you cut the fuel flow by even 15% on that 5/16" fuel line flow rate at 7 psi by internal cross sectional area, it would reduce the flow to a state where maintaining more than about 275 hp would be rather difficult, and thats assuming the fittings and fuel filter are negligible flow restrictions and the fuel system was working at nearly ideal capacity.
on anything over 350 hp but under 450hp, youll generally want a minimum of 3/8" feed and a 5/16" return line from a fuel pressure regulator
any thing north of 450 hp but under 600 hp would be best handled with a minimum of a 1/2" or AN#8 feed and a 3/8" or AN#6 return line as you always have flow restrictions in filters and line fittings, this chart shows you only need about 45 GPH to provide fuel for a 500 hp engine , but thats the required fuel flow at the carbs inlet port and it assumes thats provided at about 7 psi, at wide open throttle, inertial loads ,filter restrictions and internal fuel fitting restrictions generally reduce flow from the fuel pump by 35%-60% of what left the fuel pump by the time it arrives at the carbs inlet port.
a fuel pump that is rated at 50-60 gph would almost never be used on a 500 hp engine under real world conditions as its almost sure to prove woefully inadequate
once again you see a vast feild of links and your temped to ignore them, that may be a huge mistake, theres a good deal of useful info in those links and sub links
as usual ,knowing how to isolate and test will prove to be a very important skill!
("as will reading links so you know what to look for")
http://garage.grumpysperformance.com/index.php?threads/how-big-a-fuel-pump-do-you-need.1939/
http://garage.grumpysperformance.com/index.php?threads/setting-up-your-fuel-system.211/
http://garage.grumpysperformance.com/index.php?threads/fuel-pressure-regulators.635/
http://garage.grumpysperformance.com/index.php?threads/fuel-line-sizing-return-vs-feed.3067/
http://garage.grumpysperformance.com/index.php?threads/return-line-too-small.10665/
http://garage.grumpysperformance.com/index.php?threads/will-the-stock-fuel-system-work.11112/
http://garage.grumpysperformance.com/index.php?threads/fuel-pressure-inconsistant.10401/
http://garage.grumpysperformance.com/index.php?threads/tubing-fuel-lines-and-flaring.1030/
http://garage.grumpysperformance.com/index.php?threads/car-falls-flat-in-third-gear.9326/
http://garage.grumpysperformance.com/index.php?threads/replace-fuel-pump-or-not.8331/
http://garage.grumpysperformance.co...-wonder-whats-inside-a-manual-fuel-pump.5365/
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