Quote:

Originally Posted by HeyYou

Read this article.

Show me ANY proof that this article is wrong. Show me dyno results that don't show any improvement. Good luck with that.

That is an interesting article.....

FWIW my only 2 experiences with shorty headers was 1. on a 92 corvette, and at the track it showed 0 improvement. But then again, the factory manifold is not a bad design on the corvette. The second experience was on a 90 ford, 351 engine. Couldnt tell any difference, (based on the butt-o-meter) but I had nothing but problems with leaks, both warpage, and cracks in the tubes. This was 20 years, ago, and they were pacesetters..
Do you have any experience with any of the stainless, shorty headers? The ones I see on ebay advertise 3/8 flange. Just wondering how they would hold up? The price is right!!

Carrying this one step further, I would like your opinion on this idea.
Take a set of the ebay stainless headers, cut the flange off. At this point would basically have a 2.5in slip collector. Then have an exhaust shop make up the down pipes from there in 2.5 in. That would allow for a true 2.5 in dual exhaust.

 

The vette exhaust manifolds were pretty darn good from the factory.

Now, JUST installing shorties probably isn't going to give you a noticeable improvement on the butt-dyno. The gains just aren't that big. However, having them will let you get more improvement from all the other mods you do as well. Everything works together. I have shorties on my 98, and that thing just has GOBS of low-end torque..... and pulls all the way to redline. (a whopping 4500 RPM....) But, it's the 8 liter.... so, it had a boatload of low end from the factory, don't know how much of an improvement the exhaust was. (but, I am sure there is more to be had, as the OP that put the headers on, also did dual exhaust.... nice thought, but 2 inch pipe? Really??? 2.5 inch is in it's future.......) Would I put stock manifolds back on? Hell no.

If you can cut the flanges in such a way that you can connect 2.5 inch pipe, and do it without leakage, I suspect you will see some improvement in torque, and it'll sound better too.

The trick to get even the cheapy headers to seal up, is good fasteners and gaskets. The Remflex Dead Soft copper, or aluminum, with some quality header bolts, and you will be leak free.

 

Here is a picture of a slip style header.


My thoughts were, by cutting the flange off, then the exhaust could be a true 2.5 inches. I believe the factory exhaust, especially for a 5.9 is pretty restrictive.