[Aussie Mike]

I remember when that header test was done for Street Machine magazine. It was several years ago and there weren't many larger sized headers available then. I believe the only real tuning program was still LS1 Edit. It was also a bone stock 5.7L LS1.

Tuners have been making more and more power since then as they have learned what works and how to get the most out of the various tables available to them. Newer versions of tuning software have also opened up more of the ECU to adjustment.

I don't think rule the years of development done by people on LS1 engines in Commodores, Corvettes and Camaros just because it hasn't been done on an LS1 installed in a Cobra?? that makes no sense. The rules are still the same, a primary tube of W diameter with a length of X int a collector of Y diameter and a collector length of Z. It doesn't really matter what car it's installed in.

I think the biggest impact on low end performance is the Side pipes. They just don't have a long enough collector area. From memory that collector really needs to be about 15" long

As has been pointed out, none of these motors stays standard for long. Les, you yourself have several times mentioned to me that you plan on changing out the lazy factory cam in your L76 to wake it up. So I think an exhaust should be built to fit the end product rather than what works now Unless you want to spend more money on another set of headers down the track.

It doesn't matter to me either way if people buy Ian's headers or not. They seem like a reasonable buy for the money as long as you aren't chasing all out performance. What got me fired up on this tread was Ian's arrogant response.

Honestly though who needs more bottom end in an LS1 powered Cobra. My low end robbing 1 7/8" headers still make the car turn the tyres in any of the first 3 gears from bugger all revs so I think I've got enough bottom end. I reckon mid range and top end are going to be far more usable. It's a formula that has been working well for Ferrari and Lamborghini. They design their cars with smaller capacity multi cylinder engines that rev to buggery and make heaps of mid range and top end. Bottom end grunt is great for towing stuff and getting a heavy car off the mark but my Cobra weighs about 800KG less than a commodore and I don't own a pop top camper.

Cheers