Larry, you right about the tail pipes and exhaust gas temperatures. Once the gas has hit the muffler, everything from there is out doesn't matter much. Our race cars never seen the any difference from 2 1/4 to 3 inch pipe. The bigger the engine of course, the bigger the pipe needs to be, but I am talking 455 plus cubic inches.
As you and some of the other true racers have seen, a stock 230 or 250 will not see any difference no matter what pipe you put behind it. Headers need to be true headers, equal length and sized for the rpm range of the engine. Oversized tube size can kill a engines power curve just as fast as a undersized or stock manifold. With out a intake, cam, carb, and ignition change, it just won't matter!
As for H or X pipes, we have seen first hand how well they work, they are quieter, and make more power over a separated exhaust system, Period! As for redirecting the exhaust back to single pipe restrictions levels, thats crap, both types of cross over allow the gas to exit out the pipe with the least resistance at any givin time. In reallity, you are giving both sides extra pipe so its like four tail pipes instead of two. They work just as well on low rpm torque engines as well as big rpm race engines.
Six cylinder engine may not ever see the gains a V8 does due to the odd firing order and number of cylinders, but it sure can't hurt. Its been proven on the dynos and at the track.
Straight Axle 63 hit right on the head, if you are comparing 40 year old test or even 5 year old data, you are behind times. Just look at what has happened to oils in the last couple of years. How many 9 second street cars were around in the 70's? How about 12 second diesel pickups? All I am saying is, times have changed and so has a lot of thinking..... go to the track and test it your self.
Joe
