Exhaust headers, LS series engines

[Classic Revival]

We have an over supply of exhaust headers for the LS series engines due to the fact that we had to have so many made to keep the individual cost down. The are mandrel bent in one section, except for 1 tube on each bank which has a tig joint. A couple of images of these headers are on my gallery.
There is a limited quanity available for $800- pr plus freight. Let me know if you are interested.
Cheers,
Ian

[boxhead]

Ian, Does that price include GST?

[Aussie Mike]

What size are the primaries on these Ian?

Cheers

[Classic Revival]

Yes, the cost includes GST but not the freight.
They are the 1 5/8 primary, these work far better than the larger size producing better low end torque & a wider rev band.
Ian

[Plums]

Not wanting to "start" anything on here, but can you provide us with proof that the smaller size is "producing better low end torque & a wider rev band"???

Your statement "may" be slightly true for engines running a Completely Stock PCM, but most people won't leave it like that for too long. Your "far better" statement is a bit of a stretch.....

In my experience (not opinion), for a well tuned stock LS1 (ie. a good MAFLess tune), 1 3/4 inch pipes provide the best overall performance. Even larger if you are running an aftermarket camshaft or you're chasing maximum effort unopened power levels.
If you're running a stroker or hefty head and cam package, 1 7/8 inch headers would be the smallest I would use...

[Aussie Mike]

I spoke with Darren Difillippo when I decided to build mine and he recommended 1 7/8" based on what I planned to do with the motor. Back then most people on the forums were recommending 1 5/8" or 1 3/4" for stock engines. In recent years as the tuners have got the feel of these motors the primary and collector sizes have been gradually increasing. 1 7/8" is pretty popular now and I think Darren saw that coming with the requests he was starting to get from tuners.

Cheers

[LoBelly]

Proof is a tricky word Plums (but not as tricky as trying to work out what you intend to achieve with your post)

According to the first definition I struck at Dictionary.Com proof is 'evidence sufficient to establish a thing as true, or to produce belief in its truth.'

I don't know why it would be that your claim of experience should be considered to be proof and in any way a valid challenge to Ian's assertion.

I'm not sure what anyone is to make of your concession that Ian may be 'slightly true' - how many shades of true is there.

Here some opinion for you ...

I think it is particularly cheap to say 'I don't want to start something' and then go demand proof when you wont hold yourself to the same standard

In any case he's just letting people know about some headers - if you're convinced your larger primaries are better fine - give us the data.

Personally I'll be very surprised if there is a large enough sample of LS1 cobras to perform any meaningful assessment on the relative merits of header sizes in all applications.

Of course, I'm often wrong - so surprise me

thanks

LoBelly

[Plums]

Gee whiz bang...

Sorry for the tricky post Lobelly. I apologise profusely for posting information that may be confusing.

Here is my new post that should cause no confusion:

[Start post

In my experience, 1 5/8 inch primaries are too small for an LS1.
If you are towing a caravan with an LS1 powered Adventra they'll be fine, but for anything else they're too small....

End post.]


Does it matter to me if people buy these headers? No, not at all.

Will the engine run with them? Of course it will. In all honesty, the difference between the different sizes isn't that much.

Why did I post in the first place? I just want to see my Darkside brothers get the best performance possible. Isn't that what we (Cobra people in general) are all about???

Do I think I'm qualified to comment on this topic??? I may be up myself here but yes I do. Firstly, I have tuned hundreds of LS1's. Secondly, (and probably more pertinant to this discussion) I have spent years doing R&D specifically for the LS1 with Pacemaker headers.

Edit: My "slightly true" comment relates to the fact that some cars running the factory program make slightly more torque with 1 5/8 headers as oppossed to 1 3/4 pipes. By slightly more I'm talking a few Nm's at the wheels, and only on some cars.

[pneall]

Plums,

I would be interested in your thoughts on side pipes vs a properly designed under car system that has a cross over and properly designed collectors.

I am running 1 3/4" primaries on my sidepipes and on the dyno lost a fair bit of torque down low.

Regards,

Phil

[Philm]

I agree that the primaries seam to small, if you are looking for all out performance.

There are many cobra builders out there that are buliding cars that are not about all out performance. So these headers would work.

I am on my soap box now,

All claims aside, to buy a set of mandrel bendt Headers to fit an LSI in a Classic revival for $800.00 is fantastic, the fact that they are available is amazing. I hope this is a trend that continues, so that parts like this become available, it will take a lot of stress out of building your kit.

If you want real power though, you need to get A FORD.

Phil

[sambo]

This is quite an interesting discussion. Perhaps for Ian's sake any replies on the exhaust design Phil is asking about can be put into a new thread? I'm genuinely interested myself, as I'll be looking at exhaust options very soon.

Paul

[Rebel1]

To add a little science to this debate read here:

http://www.popularhotrodding.com/eng...exh/index.html

[Tenrocca]

Originally Posted by Philm

If you want real power though, you need to get A FORD.

Phil

Any more ridiculous inflamatory comments like that Phil and Ill get the mods to close this thread

Seriously - This should lead to a very interesting and usefull discussion.

Plums, Would you say that most of your experience is with a undercar exhaust, and do you think the patterns or trends in performance in relation to header size hold true for a side pipe exhaust system? (Could be just rewording PhilN's question there)

[Aussie Mike]

I believe the idea of a crossover is to increase flow by letting the exhaust pulses travel down both sides of a twin system. Since only one cylinder fires at a time the exhaust pulse doesn't upset the flow in the other side of the system. The main advantage being you can run a quieter more restrictive exhaust that will flow as much as a louder less restrictive twin system.

With the limited space and ground clearance I reckon you would be hard pressed to build an underbody system that will out perform a set of sidepipes. For us I reckon a set of free flowing pipes bolted on for the track are an easier option.

I think $800 is pretty good value for a set of off the shelf headers. The factory doing the bends should be able to use the same cnc program with a larger set of dies and produc
e 1 3/4" and 1 7/8" and you would have everyone c
overed.

Cheers

[sambo]

Originally Posted by Rebel1

To add a little science to this debate read here:

http://www.popularhotrodding.com/eng...exh/index.html

Les, that is a ripper of an article... if only I had the ability to put all that theory into practice.

[Cobra.au]

It will be interesting to see how my 2" primaries and 3" straight through ( and metalcat) system go on the dyno .

[Plums]

Under-body vs Sidepipes? There is a discussion all of it's own. Basically, sidepipes are short and usually large in diameter, this combination is not good for low-down torque, and in many instances can hurt the top-end too. The lack of a cross-over hurts too.

As usual, Mike has hit the nail on the head with his cross-over theory. For the average Commodore running an LS1, a well designed cross-over system will win every time. Perhaps not for power right up at peak RPM (some other designs may win out there), but average power under the curve the cross-over definitely wins.

As for this "pipe size" discussion, I don't know that any of us will ever agree.
One thing I discovered during R&D sessions with Pacemaker, was that LS1's generally don't conform to normal header pipe theory.
Pipes that we thought would work well, were often outgunned by pipes normally reserved for the race track. Some of the reasons for this I'll have to take to the grave with me, as they are commercial-in-confidence.
Here is something to consider though: Many years ago, people were putting 1 5/8 pipes on 5 litre Holden engines (that was considered the norm). These engines produced 165 kW, or 185kW later on. The LS1 power has ranged from 220 kW up to 260kW.

For Pneall, I am interested in your case. What size pipes did you start with before you went to the 1 3/4 pipes? Did you just go up in primary pipe size and everything else remained the same ie. sidepipe size, collector size etc.??

Cobra.au, with the power you're making I think you've made a wise choice...

[Rebel1]

And what's worse Sambo is that we have bu$$a all room or spaces to fit the optimum exhaust system.

[sambo]

Les, if I can swing it with my chassis design I'll be going for a well made underbody system and some 'cosmetic' sidepipes. I'm told it's better for the right eardrum as well.

[Rebel1]

Exactly what I'm doing Sambo.

I'd never forgive myself if some young child stepped up on my working sidepipes and fried their feet.

Besides, mine is a street car, wanna cruise, take things easy, blow off the occasional rice burner and the odd ford.