fuel line size ?

[1981silverz28]

I have an 81 Camaro with sbc ,750 holley,175 hp of NOS .I have a mech fuel pump (120 GPM @5.5-6.5 psi).I put a 4-7 psi safety cut off switch at the fuel solonoid and there is not enough pressure to activate the system.Will the stock fuel line from the tank supply enough fuel for this or do I need a new tank and line?

[Adam's 55 Chevy]

Assuming you have about 300hp on the motor (maybe more?) adding the 175 of Nos will push you close to if not over the 500hp mark. As you know your fuel line is as good as it's smallest restriction. I would imagine your fuel line is only 5/16" or if your lucky 3/8". I would run a minimum of -8 from your tank to the pump - regulator and -6 from the reg to the carb inlets.

You dont need to buy a new tank but you should get a bulkhead fitting in -8 in there. Some places don't like working on gas tanks for obvious reasons but empying it of gas, taking it out, filling it with water and using a battery drill should be ok to open the outlet to accept the fitting but BE CAREFULL! Once it's opened up, a step drill bit can do this to provide a snug fit, clean any shavings out. If you temp remove the sender unit you can probably reach the back side of the fitting to tighten it. Use fibre washers each side to avoid leaks.

I would tap the nitrous fuel before the reg so it gets full fuel pressure.