I have a 71 that I have dropped a 280 motor into. It runs so quite. It has the orginal double muffler set-up. I was going to take it down and have the exhaust changed to 2.5" and a single generic muffler. I got to looking at the orginal manifold that would still be there, looks small to me. Does a header give much more power? Where is the cheapest place to order z parts? I tried to buy a gas cap yesterday for the 71, it was 37+tax seems a little steep to me. thank you for the infor.

Back when I could drive my Z, I did the same thing. I replaced my stock header with a Motorsport 6-to-1 and 2.5" exhaust.

My power increase was very dramatic. I could tell that the car was breathing a lot easier -- especially during acceleration.

As far as noise... I could tell a difference. My car was louder, but it hummmed to a nice tune. Sounded strong and healthy instead of weak and choked.

I can't give you scientific numbers, but headers are usually a lot better than stock (for the early Z's anyway) because they are tuned for the car. All the pipes are similar in length to create a balancing effect.

Your other options include a 3-to-1 (6-to-2) header and a 2.25" exhaust. I have heard that the 2.25" exhaust gives you the same benefits, but it's not as noisy. IMHO: You can just buy a better muffler and use the 2.5" system.

If you buy a header from the internet, make sure it has flange thicknesses that match your intake manifold. My Motorsport header had a thinner flange and it caused problems for me. The flange is used to bolt the header to the head. There are about 4 bolts that hold the intake and the exhaust header to the head (they share the same bolt). If one is thicker, the bolt doesn't fit right.

Anyway, that's my $10 worth. I'd say go with a 2.5" exhaust and buy a good muffler. Definately go with the 6-to-1.

[m]