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Fuel line size ??


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I think I know the answer to this one, but I?d appreciate your comments to see if I?m missing something. I?m kind of new to the performance side of the hobby, but I have experience rebuilding stock engines.

I have a ?55 Buick model 48 and decided I wanted a little more power (second childhood <img src="http://www.aaca.org/ubbthreads/images/graemlins/grin.gif" alt="" />). I built a 1963 401? Nailhead with a Poston cam (2000-6000 power range), Offy 2x4 intake with 500cfm Carter AFB?s and stock exhaust manifolds. I?m running a B-W Super T-10 4-speed and removed the torque tube and installed an open drive shaft with ladder bars. I?m running the stock rear axle with 3.36 gears. The carbs are linked to act together, not progressively linked. At normal speeds and acceleration, the car performs perfectly. When I stomp on it, the engine spits and sputters ? sounds like fuel starvation <img src="http://www.aaca.org/ubbthreads/images/graemlins/confused.gif" alt="" />. I?m using the stock 5/16? gas line from the tank to the stock fuel pump. I?m guessing I need to put in a 3/8? or even a 1/2? line to the fuel pump and 3/8? from the pump to the carbs. Any advice, comments or suggestions would be greatly appreciated. -Bob

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There is a very good possibility that when you go to wide open throttle the velocity of air going by the jets is not enough to pull fuel. If you can leave the line at partial throttle and then floor it , you may need more fuel delivery by the accelerator pumps. If the fuel line is too small ,or the fuel pump is not up to the task of delivery, you will feel the engine quit as ithe RPM reaches the critical point. It will feel like you turned off the key. Then if you let it recover a bit,the power should come back

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Joe,

Thanks very much for the reply and advice. If the #%* snow and cold ever stops, I'll be able to make some carb adjustments and give it a shot. Do you think 5/16" fuel line is too small for 2 x 500cfm's?

Thanks,

-Bob

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If you have the stock cam and exhaust manifolds, I believe the 5/16 line will be good enough for everything but a long (think Bonneville)top speed run. Dual carbs have the advantage of having two float bowls for storage, which helps.

I used to run a Caddy engine with 4 carbs and a 5/16 line and it didn't run out of fuel until it got over 5,800 RPM

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