LS1 Powered S14 by SicBastard

7 minute(s) of a 390 minute read

Headers: 

I'm going back and fourth between three options:

1. I found these guys Custom Headers Built To Your Specifications

they have a neat idea, they send you mock up kit, you position all the tubes where you want them and mail it back. All said and done in stainless for $1300+s&h with merge collectors. Plus the fact that they purge weld the headers is pretty bad ass.

2. But then I also have an old set of plain steel headers that some guy had for an OLD gm F or B body LS1 swap. They do not fit at all, but I scored them for $100 and figured they'd make a good starting point with the flanges at least. Plain steel headers always seemed like a waste of money to me. I don't care what you coat/paint/wrap them in they will be rusty within a year. Rust isn't the end of the world, but in a car that gets used rain or shine I don't think steel headers last much more than 6-7 years. It would take probably another couple hundred in j bends and collectors to make them. 

3. My third option is to just drop the car off at Kooks or American Racing Headers here in Long Island. MINIMUM of $1500, and I'd have the least control over where the collectors end up.

Also, does anybody have any software to help determine tri-y vs 4 into 1, and primary and collector lengths?

7/13/09

So it looks like Kooks is way down in NC now. I called the guys at American racing headers, in nearby Amityville Long Island. They were very cool and said that I could come down and try any of their LS headers (they make like 10 different ones) to see what is closest. And if nothing quite came close enough they could do a total custom job in 5 days for around $2500. That is about the going rate these days. While it's a lot of money. Five days of a professionals time costs. This is a bit of a DIY project though and right now I'm leaning in other directions.

I'm going to do a little multi post series on header design, starting today with choice of materials:

You basically have two choices. Stainless or Plain steel. Most people think that the only advantage plain steel has over stainless is cost (almost %50), but they are wrong! Plain steel is also a bit lighter than stainless! Even given these two advantages I’ve always thought that making headers out of plain steel was a waste of time and money, mainly because plain steel headers rust like motherfuckers. Some would say, “well then just coat it.â€Â 

When I was woking at TTP back in Jersey on all the hi dollar LS1 cars, I was lucky enough to become the header bitch. I swapped out a lot of headers! And I don’t care what coating was used ( I saw at least 4 different kinds), rust was visible through the coatings with in a year! Bogus. 

“Ok don’t coat it then, wrap itâ€Â you say. While I have to admit that I love the old school hot rod look of fiberglass header wrap, it’s murder on steel headers. It basically acts like a big sponge soaking up whatever oil and water comes its way, and then holding it against the header. Can you say instant rust? While header wrap will reduce under-hood temperatures and improve looks, it also shortens the life of your already ‘livin on borrowed time’ plain steel headers.

Now if you’re building a circle track race car with a short expected life cycle, or you plan on a different set of headers in a couple years, save some bucks and weight and go with plain steel.

In my hopeless attempt a fiscal solvency I thought about going this route, and even picked up a set of steel headers that I thought I would use the tubes from, but obviously I’m having second thoughts. The advantages of stainless include better heat insulating properties, and corrosion resistance. Plus, they look damn nice.

More on header design to come…

7/14/09

What I don't know is: Presuming you know what rpm your top end is tuned for, what rpm do you tune the headers for? The same rpm? A little before or after? How little? Or do you just forget what you know and try to get a bump where you think you'll need it in the powerband?

I thought that it was interesting that in his book on intake manifolds David Vizard seems to pull no punches in stating that an intake is almost secondary/dependent to a good exhaust scavenge.

Here's what I've done so far.

I pulled David's "How to Build Horsepower vol 2., Carburetors and Intake Manifolds" down off the shelf and used his formulas to determine what rpm the stock intake manifold was tuned to. 

Based on my measurements:

LS7 stock plastic intake runners (7 of 8, the first runner is shorter)

Outer radius 312

Inner radius 188

Average = 312 +188 = 500mm/2 = 250mm plastic intake runner length

161.5mm tract in head from intake valve to gasket 

Total = 250 +162 = 412

412mm = 16.22â€Â total intake tract length

Head ports

Intake: 61x35mm= 2135mm^2 = 3.31 in^2 = same area as a 1.81" square

Then using an effective cam duratio of 260 (a comp XER 238 @ .050 lobe, is 287 advertised - 27 = effective) which is pretty close to what I plan on running I cam up with the following tuned rpms at the respective reflective values:

rpm @1 17459.85401

rpm @2 8729.927007

rpm @3 5819.951338

rpm @4 4364.963504

rpm @5 3491.970803

rpm @6 2909.975669

rpm @7 2494.264859

rpm @8 2182.481752

If I was going to try and match the headers to the intake/cam the 3rd reflected value is the only one that makes sense for me. I'm building this motor for a RWD time attack car that will be limited to street tires. So bottom end isn't too important, and I was actually planning on building the motor to drain a little power down low to pile it on later, towards a 7100 rpm redline when I have a chance of putting it to the ground.

Just a side note. The stock LS7 comes with a 211 @ .050" intake duration. If you presume an effective cam duration of 237 (211 + 51 should get you pretty close to an advertised duration, then subtract 25 to get effective cam duration, cuz intake valves don't start flowing well the very second they are off the seat) the 3rd reflected value comes out at 6110 rpm. Pretty neat since that's about where most LS7s peak even with bolt ons. I guess David's math works!

LS7 on the Dyno:

rpm----tq---hp 

3000--455--260 

3500--467--311 

4000--504--383 

4500--526--451 

5000--529--503 

5500--512--537 

6000--480--548 

6100--472--548 

6200--463--547 

6300--454--544 

6400--445--543

Dyno results stolen from here:

LS7 on the Dyno 

Thanx for reading guys, now what rpm do I tune the headers for?!

Stan helped me a bit over at gofastnews.com

The formula I was using: 

rpm * rv = [(720 - effective intake duration) * (.25v * 2)] / (L + .5* intake port D)

I did use 1300 for V. Should I be using 1141? It is a plastic intake, and I will be using a good cold air intake isolated from the engine bay's heat. Your clarification for the port diameter makes sense too. I found this speed of sound calculator

Speed of sound in air and the temperature calculator air pressure - table density of air calculation acoustic impedance air density sea level - sengpielaudio Sengpiel Berlin

115 F makes more sense to me for air deep inside a well fed plastic manifold, which comes out to 1175 f/s

Inputs:

speed of sound 1175

.050" 238

advertised in. cam dur. 287

effective in. cam dur. 260

intake length 16.22

port diameter 2.0529

Unfortunately it look even worse now. I don't need no bumb at 7800 rpm!

rpm @1 15669.89148

rpm @2 7834.945742

rpm @3 5223.297162

rpm @4 3917.472871

rpm @5 3133.978297

rpm @6 2611.648581

rpm @7 2238.555926

rpm @8 1958.736436

But the question remains. Do I tune the headers to the rpm of the intake's RV=3 rpm, or something else?