i have one more thought on this and its a stab in the dark so don't hate me. Keith what exhaust is being run after the headers? this could be where the difference in numbers is coming from. are all cars equipped with the FM full exhaust? could this be your limiting factor regardless of header choice? there is a nice hp difference between 2.5"-3" exhaust systems when you get above 450hp. again just a shot in the dark.

WOW.................
I need a good laugh every now and then!

Just to clarify the Sanderson shorty header was created at my request in early 2002 when I was doing the LS motor in S-10's.
Later when we developed the LS in the Miata chassis we found with a small dimple in #1 primary would allow us to use the same shorty.
With a 3" collector 14 to 19 inches we were able to keep a square HP/Tq number.
At this time we had no clue there would be hundreds of these sold for the V8 Roadster.
FM did a rework of this headed for there set up.

I fill sure all are aware of the KOOK family and what they have done for the car industry!
Papa Kook designed our headed within the perimeters he was given... quality and performance of the Kooks for a off the self header are unsurpassed!
For a side note I have a small history with the LS family of engines. Hands on builds of 300 plus... Camshaft design,cylinder chamber and runner porting,intake manifold flowing, 527 wheel power from a 5.7 na motor (race gas)
Out of 10 intakes there can be as much 2.5 to 5% power differential.
Crate LS3's are all over the chart, as much as 30 whp. different engines with the same cam is not data worth a nickle.
I will enjoy a real comparison.... I know the #'s
You cant bull sh&t me!

Steve
V8R

Steve,

Is there any photos of the ground clearance of the V8R LT's on an NA? I'm curious what "a little bit lower" on the passenger side equates to..

I'm inching closer to finishing my 5+ year swap and I've got the FM Elvis development exhaust with the original shorties.. thinking my GTO LS2 with a VRX4 cam is going to want more tube but I don't want pipes hanging low. I'm willing to 'adjust' the bellhousing within reason to get it.

Photos would be helpful!

Wallyman

When I swapped heads over to the square port LS3 heads I also swapped out the cam. HP at the flywheel went up to 490 and, at that point I quit worrying about the exhaust. Why? With 490 HP on tap in the front office of a 2300 pound car you just can't tell if you lose 50 or so. So, who cares? I surely don't. The Sanderson shorties fit, do not interfere with the steering ans placing the muffler under the driveshaft in the tunnel in front of the diff is neat and does not hang down. Transition from 2.5 in dia. round tube at the muffler outlet to oval tubing of the same cross sectional area gets you around the halfshafts and diff mount and gives you a place for the resonators behind the diff which you will likely need to be sound level legal on most tracks out here in the southwest.

Yes and no. On the one hand, 50 hp is harder to differentiate in something this crazy fast. On the other, why do something half-assed on a project like this? I have a set of V8R long tubes on the shelf, and they're going on as soon as I get time. LS motors like long tubes, so I don't see why not to run them.

This.

And this.

The FM tune also leaves a lot on the table. ...at least on Bert it did. A lot of that was pretty conservative timing.

But not adjusting the tune for the LT's? Hate to add to the 'internet common knowledge' but it was my understanding that the gains aren't truly realized w/o a tune (?).

And Keith's car being a "dyno king" is telling. These are crate motors. As said, their will always be variances. Keith's car has been run too. Was the other a new crate motor? They need time to loosen up (again with that internet common knowledge).

I think I need another V8M to test on though. :naughty:

Dyno results on the V8 Roadster long tubes have shown around 20hp gains on a stock LS6 over the typical 1.5″ dimpled shorter primaries. 20 Horsepower. That's all? So my answer is Half Assed? No, but spending an extra $700.00 on those long tubes for 20 horsepower strikes me as really stupid in a car that's already stupid fast.

Some would say putting an LS in a Miata is really stupid too. What makes sense for a car is a highly personal decision. I was at 445 at the wheels and wanted another 200. :sign0184:

Aside from the power gains, there are other benefits as well. The overall feeling of the engine with long tubes is enhanced, in my opinion. The engine wanted to rev quicker and felt smoother overall. The long tubes gave a increased feeling of "quality" to the build. Totally subjective, I know. Any build I was doing that leaned toward sport or competition I would definitely spend the extra money. There are other choices for a reason. The other headers, and even cast manifolds, might suit your build goals better. Not everyone is looking for the same end result.

Aside from the power gains....yeah right. 20 HP according to the supplier

The long tubes gave a increased feeling of "quality" to the build...
I could think of a better way to spend $700.00 and when I was done I would get a lot more than 20 Horsepower for my money.

Sounds like you're in love with yourself and your choices but I don't think I have ever seen a larger pile of fertilizer in print before. As for my car, this is the only view most people get:

Pass the popcorn!

No popcorn needed. It's his car and his money. Spend it as you see fit. I don't see why there is any need to be a jack ass because someone has an opposing view point. That's why there are choices out there. Your $700 might be best spent on a personality upgrade.

Strict numbers like "20 hp" mean nothing to me unless it comes with some data about where that increase is, and whether there are any losses in a 1:1 comparison. 50 hp and I'll look the other way - lol. If you're chasing a peak number that's fine, but I think most street cars like a thick/usable power band.

I also like when people go to the effort to "science the shit out" out of stuff. Words mean very little unless you can back it up with facts. :sign0184:

Finally! A man after my own heart.
When I was building my engine I picked up a pair of used L92 heads from the local Pick-a-part for next to nothing and sent them off to Racing Head Service for new seats, to be ported, polished intake and exhaust ramps and stuffed with new valves and springs. Here’s the tale of the tape when I got them back:
4.030” test bore
Lift ___.100 _.150_.200_.250_.300 _.350 _.400 _.450 _.500 _.550 _.600 _.650_.700_.750
#1 Int. 74.9 109.4 154.4 193.5 225.3 252.8 274.6 292.7 308.8 321.0 328.7 326.6 310.0 316.6
#1 Exh. 63.6 97.9 126.1 148.7 162.3 178.6 189.6 197.6 205.5 210.7 214.6 217.8 221.2 223.5
The intake was tested with a radius plate and the exhaust was tested with a 2 ½” stub pipe.

Valve dimensions:
Intake = 2.160” X 4.870” X .314”(8mm)
Exhaust = 1.590” X 4.920” X .314”(8mm)

Seat/throat diameters:
Intake = 1.870”
Exhaust = 1.355”

Volumes:
Intake runner = 260.6cc
Exhaust runner = 90.0cc
Chamber = 69.8cc
Cylinder Bore=4.065 in
Stroke =3.622 in
Ther reason for dragging you through all of this is ALL of the info needed to correctly size the exhaust header primary tube diameter, tube length and collector size is right here and on the cam card for my engine. Volumetric efficiency does enter into the picture but for a four stroke-cycle engine it is NEVER below 75% and if any tuning of the intake has been done it will be about 95%. For those of you that don't think the stock intake on your LS motor is any good you will be sadly mistaken. That bright new FAST intake that you put on your new streetfighter will bring that number up to 98%. Not much return on investment there UNLESS you're on the track. Then that part will give you about 36 more ponies above 5800 rpm. On the street, you will probably see the inside of a police station before you see those extra ponies.
On my mildly 'breathed on' LS2
EVO is 57.5 degrees BBDC
Exhaust Valve Centerline is 122.5 degrees

So, let's find the diameter of the header primary tubes:
Cylinder Volume = displacement ÷ number of cylinders
Ac/s = (cylinder volume x RPM) ÷ 88,200
Or RPM = (Ac/s x 88,200) ÷ cylinder volume
Where:
Ac/s = primary pipe c/s area
Cylinder volume = volume of a single cylinder
88,200 = mathematical constant
RPM = RPM at torque peak for a daily driver or Max RPM for your track-only racer

Once we know the calculated c/s area we can calculate the corresponding primary pipe diameter to the nearest available pipe size.
If Area = diameter2 x 0.7854
Then pipe size equals the square root of the previously calculated c/s area times the reciprocal of the constant 0.7854.
Pipe Size = v[A x (1/0.7854)]
Or
Pipe Size = v(A x 1.273)
For a peak at 4400 RPM
Your Primary Tube Diameter is 1.45 inches
for a peak at 6000 RPM
Your Primary Tube Diameter is 1.68 inches


These numbers should look familiar.


There is also formula for calculating a preferred primary tube length. In his book, Performance Tuning in Theory and Practice, A. Graham Bell cites empirical formulas for primary pipe length and diameter that yield ballpark results surprisingly close to the previously examined exhaust volume and VE formula.

Lin. = [850 (360 – EVO) ÷ rpm] – 3
Dia.in. = [(vol. x 16.38) ÷ (L + 3)25] x 2.1
Where:
L = primary pipe length
EVO = exhaust valve opening point from cam card
vol. = volume of a single cylinder
Dia. = calculated primary tube diameter
OK header fans this is where things get interesting and all of the folklore surrounding 'the quality of long tube headers' gets debunked.

For your daily driver with a trorque peak at 4400 RPM Your Primary Tube Length is 46.97 inches
And for all you race fans, your Primary Tube Length is 33.60 inches.

Yes, Bunky those 'long tubes' get shorter as the exhaust pulse frequency increases. Now let's see what's up with collector diameter and collector length.
Collector Diameter ~ 1.9 x primary pipe diameter
Collector Length ~ 0.5 x primary pipe length

So for the daily drivers,
Your collectors are 2.75 in in diameter and they should be 23.4 inches long.
And for Ricky Racer your collectors are 3 in in diameter and 17 inches long.

Clearly using 2.5 in or 3 in tubing downstream of a short merge collector accomplishes the same result.


It is very important to recognize that the exhaust valve opening angle and duration directly impacts tube length and diameter. In fact it has a more significant effect than anything else so when someone tells you to use his headers you better find out what cam they were tested with or you are throwing money at a problem you may not have. This is why my LS2-LS3 engine uses Sanderson Short tube headers not long tubes. Not because it is a "Half Assed Build" or somehow "Lower Quality" but because that motor reaps no benefit from those headers. I used the $700.00 I saved on a set of Katzkin Leather seats covers, door cards and European carpet instead!

Now will someone just pass the F'n Popcorn?

5000 years ago everybody KNEW the Earth was the center of the universe
500 years ago everybody KNEW the Earth was flat
50 years ago everybody KNEW Jimmy Carter was a great President
5 Years ago everybody KNEW open borders was a great idea
5 months ago everybody KNEW Hillary Clinton would be the next President
5 days ago everybody KNEW long tube headers made great power across the power band and out performed every alternative.

Just think what everybody will KNOW in 5 daysl.

Yawn.

Dude, drop it. The explanation post was great, I enjoyed reading that. The rant, not so much.
Let's just respect the fact that people will spend money for parts as they see fit on their builds. That's all there is to it.

...

https://scontent.fmci1-2.fna.fbcdn.n...06&oe=596B4333

https://scontent.fmci1-2.fna.fbcdn.n...cc&oe=595EB317

Here's a pic vs the oil pan and subframe. Pretty self explanatory. They're maybe 1/4" lower then the oil pan and 3/8 to 1/2" lower then the subframe.

I sure would like to see the rest of your exhaust system. And I would shamelessly copy it. :)

Slipovers at the header with wide lap band clamps, fancy merge into a bullet muffler, a v-band before it goes by the rear so you can disconnect and remove it, and another bullet/turndown in the back. Probably a lot more livable then your dumps under the floorpan. We just bought a few stainless bends, about 6 foot of straight stainless, and cut/tig'd it together.

https://scontent.fmci1-2.fna.fbcdn.n...f3&oe=5961CFE0
https://scontent.fmci1-2.fna.fbcdn.n...e1&oe=594EF852
https://scontent.fmci1-2.fna.fbcdn.n...a9&oe=5961FEA5