Join Date: Nov 1999
Location: Central California, USA
Headers create a greater pull on the exhaust port that increases the engines abiltiy to breathe. Many years ago when magazines used to do "tests" of intake, carbs, and headers, they usually needed to richen up the carb one step to take advantage of the new headers.
As I recall, most intake and carb swaps only improved about 20hp. Usually this was after some careful carb tuning on their part.
Headers did about the same.
The more mods you do elsewhere, the more headers will help.
1 5/8" would be a good size for a 327. If you were going to rev 7000 and had a big cam and carb, 1 3/4" would be good.
You want headers that fit well, and have thick flanges to seal well to the head. Use the correct length bolts, if they are too short they will come loose, if too long will bottom out.
If you have power steering, you have to get headers to clear the box. Not all headers will clear the box.
You also need to re mount the alternator to the header bracket, make shure you have the parts you need. You may have to take the motor mount loose on the drivers side to install the RH header.
The older I get, the faster I was!