Advice on Headers

[Churchy]

Hi Gang,

I want to have a go at building the headers and sidepipes. Cobbindale has inspired me after looking through his gallery. Also, pneall has his off at the moment and I had a look, and whilst I think it is another black art, I'm going to have a go at it.

So, based on the fact that we are using an LS1 and do not intend to do anything other than cold air intake, an edit and other little tricks to get horsepower, and we are not planning on forced induction of any kind, what is the best pipe size for the primary pipes coming from the exhaust manifold.

I would think that bigger is better,to get the gases away, but again I may be showing my complete lack of knowledge.

And you Ford guys, no I won't be making them out of Aluminium

Any tips fella's

[Cobra.au]

I may be wrong but I thought if your primaries are to big it can cause power loss in the lower rev range?

[pneall]

craig, spot on. On a standard LS1 primaries should be no bigger than 1 5/8".

Mine are 1 3/4" and I loose a heap of low down torque.But they are great size if you want to modify the engine. 1 7/8 required for blown applications.

Then there is the length 32" or 36" I think is optimum and then there is the collector.

Unfortunately Sidepipes will never be as good as a tuned under car system with a cross over...but they dont sound anywhere near as good as sidepipes.

Phil

[Churchy]

Phil,

Thanks, you know what we are doing, and I agree with, I want the sidepipes, cause they look good and sound great.

If you were starting from scratch (like Pete and I are), what size headers would you do ?

De Fillipo engineering does a DIY header kit, which I am sure I can make a meal of.

Cheers

[Plums]

The quickest unopened LS1's use 1 3/4" or 1 7/8" four into one headers. My ute uses 1 3/4" four into one Pacemakers (mine is the fourth quickest in the country I think).

On the Dyno, I've found that 1 3/4" pipes only lose a small amount of torque compared to smaller pipes, but gain that back at the top-end. The larger 1 7/8" pipes demonstrate similar loses/gains but on a larger scale, (though the loss is proportionaly more than the gain). The 1 7/8" pipes start to come to life on head and cam (aggressive cam) cars.

For general street use and to retain maximum low-down torque, you can't go past 1 5/8" tri-y's, though this will present problems with sidepipes.

For the person that wants to go racing occasionally, I highly recommend the four into one, 1 3/4" pipes.

I will be running 1 7/8" pipes on my Cobra.

Just remember that a good tune/tuner can get back some of that lost torque and magnify the gains up top too.......

Geez, that was a long spiel to say not much!

[venom0427]

some of the pipes we built ran 1 1/2" into 1 5/8" thay should be 40" long, but to get a 40" in a cobra engine bay is not on, so around 36-38" i think we got, the car had the 4" side pipes (you know, the ones you guys dont like) thay ran 4 into1 x 4" with a 2 1/2" internal, to the 4" out let. this was on a 302w and a 350 lt1, both of the LT1's had the d port and the plate for the headers were around $80 ea (what the) so we got our own laser cut. barny, from barnys exhaust but a few of our exhast systems, and boy was he good, but as usual, he didnt last ether. any way thats my say, trying to put an attachment on......???????

[Aussie Mike]

I went with 1 7/8" primaries that step up to 2" into the side pipes and the collector is 3 1/2".

I went the larger 1 7/8" because I thought I might supercharge the motor later. I reckon Phil has the ideal for a Naturally aspirated LS1 with the 1 3/4" as they will give pretty good all round performance with room for upgrades like a cam and heads.

Cheers