I'm trying to find out what the psi output is of a 1968 Firebird 400's mechanical fuel pump. I don't have the original on my car but I'm guessing (hoping) it has the same psi as the stock.
Right, 4 to 6 is all the carbs need, but a mechanical can go over that. I was thinking of getting a regulator, but first wanted to see if my pump could even go over 6.5 (my carbs max).
You will only need a regulator if the fuel pump over powers the needle in the seat and causes the carb to be too full. This will cause large amounts of fuel to overflow & dump down the carb and the engine will flood badly. Is this what is happening? Honestly instead of buying a reg & fittings to install it you could spend the money to buy the right fuel pump and you will be fine (we all are).
If you want to solve any and or all fuel delivery issues you may be having, do yourself a favor. Order a fuel pump for a 73 SD (super duty) 455 T/A. This WILL bolt right up to any Pontiac block however, it has A MUCH LARGER fuel reservoir than a standard/typical Pontiac fuel pump. In addition, order the hard line that goes from the pump to the carb as well and it will look perfectly stock and you won't have to use rubber line etc.
A little trick I learned on my ole 400 in my Bird!