Exhaust headers, LS series engines

[Plums]

I agree that for many Cobra drivers, these 1 5/8 pipes will do a marvelous job. For an untuned LS1, these pipes will be a great choice.

As soon as you get a decent MAFLess tune, a step to the next size would be ideal. Why? Most decent tuners can tune the "bottom-end" with larger pipes to equal, if not exceed the smaller pipes torque gain, with better top-end performance too...
Chasing maximum HP is not what it's all about. Why not get a few extra HP up top, while still maintaining the same bottom-end performance????

All of the above relates to stock, unopened LS1's. As soon as you put an aftermarket cam in an LS1, these smaller pipes will be left behind for top-end performance.
These smaller pipes will still even work on over 400 cube LS1's, they will just strangle it somewhat...

NASSTY has absolutely and positively hit the nail on the head!!! The whole system needs to be matched. There is one problem with Cobra's, people try to make them look original by using the 2 inch sidepipe bends and the large 3 1/2 inch collectors. 1 5/8 primary pipes that step-up to 2 inch pipes then a 3 1/2 inch collector will absolutely kill performance. The laminar flow that Ian mentioned earlier will be totally lost. Even a 1 3/4 pipe step-up to a 2 inch is too much and will hurt torque.
If you wanted to run these 1 5/8 pipes, I would suggest running 1 3/4 side pipe bends....

[Rebel1]

OK....so I often get accused of being somewhat different. That's only cuz I'm the only insane one amongst us. So to keep with tradition I'm gonna put in my 2 cents worth.

Many of us have an interest in track work. That implies wringing every last bit of power one can from their engines.

But.....some of us are not into that, we only want a good street car that will blow most of the showroom cars from the road. Now, this is where I get to be somewhat different.

With regard to the Gen111 and IV Chev/holden motors the stock cast manifold has proven to be more than sufficient for healthy street work or, as plums described, an unopened but well tuned engine.

The restriction with these engines in their parent cars are from the cats back. In other words most gains can be had in the parent cars by replacing the standard exhaust system with aftermarket cat back systems.

The problem is that these standard manifolds can be difficult to use in a cobra because they exhaust backward. However, if you swop left to right you'll find in many cases they will fit and will allow a nice curved J pipe to run under the car to the cats.

How can I justify my claims about the performance factor of these standard manifolds?. Go the Australian LS1 site....do a search. You'll find plenty of comment and tests that imply that the standard manifolds are great up to the point of installing a cam.

Now....It's back to the funny farm for me, to the bees and flowers and laughing birds and basket weavers who twiddle their thumbs and toes, etc. etc. etc.

Cheers Les

[HSVREDSLED]

Originally Posted by Rebel1

How can I justify my claims about the performance factor of these standard manifolds?. Go the Australian LS1 site....do a search. You'll find plenty of comment and tests that imply that the standard manifolds are great up to the point of installing a cam.
Cheers Les

.....................Un-tuned.........Tuned
Pacemaker.......hp lbs/ft..........hp..lbs/ft

1.5" Tri-Y.........339 349.......... 364 373
1.625" Tri-Y......353 357.......... 370 379
1.5" 4>1 ..........309 341.......... 364 379
1.375"..............339 354.......... 360 374
1.625" 4>1........349 355.......... 368 378
1.75" 4>1.........340 344.......... 371 381


Sams Brand XX

1-5/8 t-y&2.5"....352 358........ 376 383
1-5/8 4>1..........344 354........ 374 380

Genie

1-5/8 4>1..........347 353....... 368 377
1-5/8 Tri-Y........345 355........ 374 382

HM Headers

1-5/8 & 2.5........349 355......... 370 379
1-5/8 & 2.25......343 352........ 372 381

Hurricane

1-½ T-Y...........346 356......... 363 375
1-5/8 T-Y.........350 358......... 369 380

DiFilippo
4>1..................343 356........ 374 381

HSV
4>1..................340 349........ 365 373

CAPA
4>1 .................356 356........ 371 377

Wildcat
1-5/8...............346 353........ 370 376

Advance
1-5/8 T-Y.........355 358........ 373 382

Hi-Tech
1-5/8...............352 357........ 372 380

Std Manifold
.....................347 349........ 367 372

**This has been faithfully & accurately pasted, with no fudging of ANY figures!

(Copied from LS1 website.)

[Rebel1]

Hey, thanks loads HSVREDSLED, guess that proves a point.

Given that often our finances are stretched and we have heaps of other things to spend money on, then that proves that using a standard manifold is an excellent and inexpensive option.

The cost of a fancy header system is better off being put towards a good CAI in my opinion.

Tis Ok if you are a welder type but to us more, ahmmmmm, academic types, then not having to make extractors/headers is one hell of a saving.

Cheers

[HSVREDSLED]

Originally Posted by Rebel1

Hey, thanks loads HSVREDSLED, guess that proves a point.

Given that often our finances are stretched and we have heaps of other things to spend money on, then that proves that using a standard manifold is an excellent and inexpensive option.

Cheers

True...for a standard engine....but who leaves them standard? You will soon get sick of standard. LS1's are so easy to get hopping through Cold air/Tunes which is reasonably inexpensive, then you will benefit from after market headers and future proof for the inevitable Cam upgrade.

[Plums]

Originally Posted by HSVREDSLED

True...for a standard engine....but who leaves them standard? You will soon get sick of standard. LS1's are so easy to get hopping through Cold air/Tunes which is reasonably inexpensive, then you will benefit from after market headers and future proof for the inevitable Cam upgrade.

This has been my point from the start...

Most people get a tune when they get VATS turned off in the PCM, this is before they have even started the thing. Most that I have done get a full custom, twin table MAFless tune.....

[HSVREDSLED]

Oops double post...

[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

[HSVREDSLED]

Originally Posted by Aussie Mike

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

For the record, I think the pipes on offer look well constructed and are a good price. If I was in the market I would probably buy them.

I guess the difference between discussing the LSX donk in a Cobra and in its usual Holden/HSV is that in the latter, every possible rwkw is attempted to be extracted. However with 800kg shed over a Commodore, Im surprised you guys get any of the neddies to the tarmac. If robbed low down torque is your dilemma, diff gear change may be your friend and keep your current pipes and increase gas velocity through higher revs.

Now I just gotta think of a way of shedding 800kg from my car.

[Rebel1]

You know....what has me bu$$ered is exactly how much is enough.

Like, I'm looking at the LS1 site and in the GM Motorsport forum. In the stickies there is a post about a SS Thunder ute with a 6 Ltr completely standard ( stock exhausts) which did a 13.9 @ 102 (about)

Then underwent a mafless tune and did a 12.9 @109.5...all bog standard with bugga all miles on it.

And all the while having traction problems!!!!!

Now this thing weighs what??....1625Kg.?.

I'll leave it to the more expert than me to guess what this same powerplant in a say....1140 Kg.? cobra would achieve.

My post clearly mentioned Street car as opposed to track cars but also mentioned being able to blow off most ex showroom cars.

Sure, most of us will install aftermarket cams etc but my point stands...the stock manifolds will not stifle a standard ( as presented for rego) lightweight cobra which can in that stage of development give a hell of a fright to most cars ex showroom.

There is another area which I suggest many on here don't realize. You can build these things...purchase the best brakes, springs, shocks and all sorts of mickey mouse stuff and I'll bet.......you $hit yourself first outing.

You'll more than likely find it wont stop, wont go around corners and you'll find yourself wondering what the hell is going on and having to spend more money than you planned on sorting the thing out.

I'd prefer to get it handling and stopping properly before I find myself short of money because I spent up big on some go fast stuff.

My point is...you really don't have to have all the best of everything ie. cams, extractors etc., to have a well performing cobra...the lack of weight is your best friend.

Cheers