Ok i currently have headders, magnaflow mufflers, but still the stock exhaust pipes. Im not sure what size they are, but they look small. Im am considering jumping up to a 2.5in exhaust system w/ x-pipe. Will i see a noticable performance increase?
I 2nd that question, I have TA headers, flowmasters, but 2.25 exhaust. Is 2.5 better? (P.s. don't mean to steal your thread, but good question)
A healthy small block can benefit from 2 1/4" pipes, no question. Having worked with cars for almost thirty years (including a stint at a muffler shop) I believe 2 1/2" is overkill for a 350 unless it's a high horsepower engine. But keep your fuel/air mixture in mind when you change to bigger pipes. If it evacuates more freely it should be able to take in more air and fuel or it won't make much of a difference.
While the subject of exhaust is up, is there any real benefit from an X or H pipe over two seperate straight pipes? The X I can kinda understand but the H seems rediculous with its hard corners. Why wouldn't I just want straight pipes?
Tough question but my sense is in order to percieve a change you would have to obtain about a 10 hp or more increase. Since you already have headers it is questionable. An x pipe will change the tone of the exhaust and get rid of some of the drone in my experience which is a benefit. Have you had you distrib advance recurved? If not, I think that might give you more of a percieved change than the exhaust mod for less money.
ok...so would a custom strait pipe system be better than x or h pipe if it was 2.5 or 2 1/4in? flynbuick- im not sure what im supposed to look at in your link...
Articles on X pipes. In theory the scavaging effect of a H or X pipe may be better than straight pipes. I am just saying you already have headers and dual exhaust. Do not expect too much from a further change. 10 horsepower would be a lot and even then you may not feel much if anything. By way of further explanation the manufacturers rated gain may be exaggerated for your engine's operating range and when added together they are certainly not cumulative. What I mean is let's say the headers are rated at 20 hp max gain , an x pipe at 15hp max gain , and the mandrel bent tubing is 5 hp max gain. This max rating gain may be at 5500 rpms for 500 plus hp engines so yours might be less. Plus when added together the individual gains are not cumulative in any case so you will never get 25 + 15 + 5 = 40hp total gain. Plus with the headers and dual exhaust you have already obtained a lot out of the total achievable gain. There is not a ton of hp gain left to obtain so your expectations may be too high.
The x pipe is suppost to be a slight gain over the h pipe which is a bit better than the striaght pipe setup (these are marginal differences though). Make sure you use mandrel bent tubing and I'd go for 2.5".
If you ever read Horsepower Handbook, theres a dyno test of an engine w/ straights, and H pipe and an x pipe. They both gained hp all through the curve (by 3-5hp minimum) but it was where they really made power that was interesting - the H made far more midrange (i think it was 10+hp more) then the x pipe, but the x was better for bottom and top. The H-pipe would definitly have a harder midrange hit but not as much top end pull. I am going with an H-pipe for my exhuast.
exhaust system What system is best is the one that makes you happy. Jim is right. IMHO the main restriction is the mufflers. the balance between each bank is good for more power and fuel economy. Unless you are racing and looking for every last bit of power, there probably isnt enough difference between mandrel bent and compression bent pipes to matter or to tell any difference on the street. I went to 2 1/4 for my riv. through out the whole system. It ran much better than it did with the factory 1 3/4 system. A half in. increase in diameter in a pipe will let it flow a LOT more.
Rizzle, I pulled that book out again and sure enough, found the article. Must not have notieced that part of the book before. The H pipe owned the midrange from about 3500-5500 rpm. If your gonna keep your car at the high end, oval track race car, go X, but for the street I'd go H. Both had an increase in power form straight pipes, but not enough that I'd bother altering a current set of straight pipes, if I already had them. But if you are getting a new exhaust then I would definately put in an H. The book also mentioned step headers, however, when the ran dyno tests, they only recorded 3000-6000 rpm power levels. So the step header they had didn't make a real difference, since they ignored the bottom end. Have any of you made/used step headers? Any significant difference in low-end?
