I have a fairly stock 87 gt. Its going to have a cam, new valvetrain in the motor. Im looking into getting a set of used hooker shorty's equal length and a max off road X pipe. What will my performance gains be? Will there be any? Will i loose alot of bottom end? Thanks in advance
If the motor's gonna remain fairly stock, don't waste your money on shorties. The stock headers, while they look restrictive, don't actually impede peak flow/performance until you get up to about 280 crank HP or so. If you know you're going to continue to make mods that will take you past that, the shorties will set you up for that. Long tubes however, should actually help the bottom end provided you don't go crazy on the primary size - 1.5" or 1 5/8". The offroad system and low restriction mufflers might be good for 5 or 10 HP at peak. Mostly, it'll sound better.
See my signature. I have tried equal length 1 1/2" MAC shorties and FRPP 1 5/8" unequal lenght shorties and lost power over the stock headers with both.