sabastian458

iTrader: (5)

I have had LG 1 3/4 long tubes on my car (bought the car with them) and it ran well (471whp 439 wtq). I bought another set of 1 3/4th from another vendor and installed. Very noticable power loss thru out. The only visual difference was the primary length runners. Lg's were much longer.

I since sold the 2nd set of headers and bought a set of Stainless Works 1 7/8th long tubes. I havent had another dyno run on this setup yet, but I can safely say that I have picked up all the lost power and then some. Down low it isnt noticable, but when the RPM's get up there is when it is felt. The car pulls much better compaired to the LG 1 3/4 vs the SW 1 7/8. I suspect that the engine is making near as much power on the SW's down low as the LG's were and then picks up more up top. Which is to be expected.

I hope to have the car dyno'ed again, but I want to wait until about the same time as the last dyno so I can compair similar conditions. (it was mid June in the south west 100degree weather when the 471/439 was put down)

I wanted larger primaries and I paid to get them. I also have learned the hard way to research and buy performace parts with a end goal in mind. The 1 7/8ths are there for my end goal, not my current goal. I am happy with them.

litle88

iTrader: (20)

Diet, can the Ls3 heads exhaust ports be enlarged without running into any issues?
I've never asked that or even read about it.

revtech101

What port is 1 5/8 inches? The oem cylinder head exhaust port?

If so, it needs to be expanded/ported to 1 7/8 inches to avoid losing velocity. After that, it could even use a different cam. Then it needs to be tuned. The "combo" has to get modified.

Remember, 1 3/4inches = 1 6/8inches.

MikeWS6

Great thread. Thanks for sharing the results.

ctd

iTrader: (1)

Why would you do this?

DietCoke

iTrader: (18)

Your privilege to type in any tech forums should be revoked.

Like, forever.

TWS

iTrader: (63)

If the dyno was worth a damn you should be able to dyno virtually any time and get a useful comparison. That's what correction factors are for. It should measure temp, humidity, etc, apply the proper correction and would be close enough to be good useful comparison.

Blk98Vert

iTrader: (2)

Another thing I have a problem with is if Lou said 1 7/8s aren't needed until 440ci why does he only make 1 7/8s for the camaro which is a 376?

82cetuner

iTrader: (9)

because not everyone with a 2010+ camaro is still at 376ci theres alot of big cube guys out there and there is a need for the aftermarket parts to support it. its not hard to get a lsx engine over 440 cubes with iron blocks these days

Ls1s never came in alot of cars but they make swap headers for them its because theres people out there that do it and there is a market

kllrvet

iTrader: (4)

According to Louis, not Lou, they make them because their customers demanded it. I'm certain if you ask them their opinion on which header to get, they will say 1 3/4.

Blk98Vert

iTrader: (2)

I know but in both promo videos for the Vette and Camaro headers no mention of running them on a 440 is ever mentioned. Even on the street series headers he says if you run heads and a big cam you want the bigger better headers.

flash911

I'm not sure this is exactly correct. Certainly port matching is always of value, but if you are expading the exhaust port you are reducing velocity. I'd bet Diet Coke would agree with me on this.

Louis is a smart guy, but besides market demand there's another reason as well: people are building larger HP motors. The formula as I was told (I'm not an engineer) is round tube moves 115 CFM/square inch (1 7/8" = 215.6 CFM) and 2.2 CFM is required per HP. This means 1 7/8 tubes support up to 781 HP (215.6/2.2x8), but 3" collectors only support 739 HP. This does not tell the lower HP limit of 1 7/8 but gives you the upper limit.

DietCoke

iTrader: (18)

1 7/8 tube is not 1.875 square inches of area, it is 2.761 square inches (and thus 317.515 cfm according to your formula, wherever it came from).

A stepped header will always make more power then a straight header, because it keeps velocity high, while also increasing peak flow. F1 headers can have as many steps as you have fingers, as they are obviously meticulously hand-made to accomodate this principle. I have 1 7/8 straight headers on my 429, but am considering switching to a 1 3/4 ---> 1 7/8 ---> 2" custom header in the future. I have no doubt it would be worth a free 10rwhp and 10tq. In the OP's case, the 1 3/4 is obviously a far superior design to the 1 7/8 which has much shorter primaries with many more bends. It isnt fair to compare the two headers, even if they are from the same MFR.

RAllen

iTrader: (5)

You guys remember this test...
http://www.carcraft.com/techarticles...o_numbers.html

Seems like pretty straight forward results from back to back testing on a very mild setup.

Blk98Vert

iTrader: (2)

The TTS are a horrible design, there is pretty much no collector. But even the bigger headers brought the torque curve down 600 rpm.

MeentSS02

iTrader: (11)

Seems like people are forgetting that header primaries are measured by their outside diameters, not inside (which is what the exhaust port/gases will interact with).

flash911

I'm no expert and I did my own math so I could be wrong. As the formula goes, it's 115 cfm/sq inch.

revtech101

Explain. I wanna learn.

Nebulus

iTrader: (14)

@OP: What compression is it running at?

No Hope

Something you should consider is tubing is sold by the OD. 1 3/4" headers have a 1.680 ID depending on the gauge of the tubing.