1 3/4's vs 1 7/8's Headers

[Jason 98 TA]

We stock the Pacesetter 1 3/4" headers & are building the connection pipes to connect the 3" TSP x pipe & 3" TSP exhaust with magnaflow mufflers. I'll let you guys know how that combo works. While it won't be stainless, it will cost just over $1000 or so for headers, x pipe, & axle back...

I'd have a hard time taking off my TSP header/exhaust system. For the money you get a header setup, 3" x pipe, & 3" magnaflow muffler'd axle back all out of stainless... How can you beat that combo????

[eynigush]

Texas Speed puts out a good product but some people, like myself, prefer to
purchase 304 grade stainless over 409.

--Eddie

[brAnd7onX]

Originally Posted by PieNsky

See post #5

I don't know how I missed that. Thanks man. I think when I get my camaro I am gonna go with the SLP setup.

[MarylandSpeed]

1 3/4" and 1 7/8" seem to perform about identical on these cars. We basically tell people if your gonna stay stock, or bolt on, 1 3/4" is fine. If your gonna mod more than that, go 1 7/8". Lastly, if you have no clue what the future holds, go 1 7/8" anyway. There is no harm..it's kinda like buying a shirt a size too big thinking your gonna go to the gym and get buff.

[JR-Vette]

Originally Posted by brAnd7onX

SLP I believe only offers the 1 3/4's headers and the more popular ones like ARH and Kooks offers 1 7/8's. I guess I just wanted to know is there really any power difference between the two or even any sound difference? Thanks.

Selecting too large of primary diameter can kill off low end torque so take the time to decide the header you want

"canned" headers out there in most cases are not even designed correctly as the longer the total header length is the smaller the primary needs to be.
Also do not be fooled by what the header is made of as it could be stainless steel but a cheap grade and SS changes shape as the temp changes and welds crack.
Many so called performance headers are made in Mexico or China with not very good welding policies.

The concept that maximum power is obtained by zero pressure in the exhaust is only partially true.
There should be absolutely no back-pressure from the collector rearward, but the diameter of the system beginning with the exhaust valve is a compromise.
The highest efficiency for the system requires a minimum speed for good exhaust gas velocity to insure that gas does not "back up" into the chamber during overlap at low engine speeds, and that the "suction" (negative pressure pulse) effect of a resonant (tuned length) and/or collector (overlapping exhaust pulses) system is optimized.

To predict what primary size will be best for a specific motor, you must know where you want the engine to develop peak torque. If the existing torque peak is at bit lower RPM than you prefer (typical in under-cammed or stock motors), it can be "bumped" a bit by increasing the primary diameter. If the torque peak is too high (motor is "peaky", with no range and poor recovery from gear changes), the peak can be adjusted down by using a smaller pipe. A change of 1/8" in the primary diameter will raise or lower the peak torque RPM by 500 or so.

This factor slightly overlaps the effect of primary pipe length, but the pipe length generally will not change the peak torque or the RPM at which it occurs. A length change has the effect of improving the torque on only 1 side of the peak by "borrowing" it from the other side. A shorter pipe improves the torque after the peak (reduces it at lower RPM), preventing the curve from flattening out so quickly as speed increases. A longer pipe extends the torque curve backwards to improve the engine's flexibility, at the expense of after-peak torque. Less stall speed is required, and the motor will pull taller gears; this re-tunes a 4-speed motor for better operation with Torqueflite, etc.

For best effect, the gas speed in the primary tube at the peak torque RPM should be about 240 feet per second.
The formula to calculate pipe size is:
Area of Primary Pipe = RPM × Cylinder Size ÷ 88,200

This determines the pipe's cross-sectional area, from which we can calculate the ID.
Typical exhaust pipes are 18ga. (wall thickness of .049"), so the OD will be .098" larger. From this we can construct a formula for an 8 cylinder motor, and factor in the 18ga. wall thickness:

Area of Primary Pipe = RPM × Motor Size ÷ 705,600
Pipe ID2 = RPM × Motor Size ÷ 705,600 ÷ .7854
Pipe ID2 = RPM × Motor Size ÷ 554,177
ID = (RPM × Motor Size ÷ 554,177).5
OD = (RPM × Motor Size ÷ 554,177).5 + .098"

Remember that your peak torque RPM will always be lower than your peak HP RPM. The separation between peak torque and peak power is roughly proportionate to your range of useable power (wider is better).

Be realistic in your estimates and plans - peak torque @ 7000 RPM sounds good, but is almost certainly beyond the breathing ability of even a professionally-built race motor, and if true will make the car impossible to launch. Note that 1-1/2" pipe is large enough for a 273" motor with max torque @ 4000 RPM. A 360" only needs 1-3/4" for 4200 RPM. A 440" is fine @ 4500 RPM with 2" primaries.
If choosing pipes for a 4WD, van, towing, etc. keep the size small to improve torque where you need it most - the lower RPM ranges, typically 2500-3500.

One exception where use of a larger pipe (than indicated by the above formula) will help power is, of course, motors using nitrous oxide, supercharger or turbocharger. In these cases, size the pipe for the expected peak torque, not the motor size.

Another instance where a slightly larger pipe may help is where the departure angle of the pipe from the flange is very sharp (typically downward). The added cross-sectional area immediately after the flange apparently helps reduce the restrictive effect of a small radius after the port. This partially explains why some header models or brands work better than others with similar dimensions.

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Minor Improvements

If possible, slightly enlarge the inside of the flange opening in the header itself to produce a sharp step (be careful of grinding off the tube weld). Do not radius the edge.
A 1/16" bevel is generally possible and will help. If there is not much room, don't grind all the way into the flange - a 45° angle is fine. This has a minor anti-reversion effect, helping to prevent back-flow at low engine speeds; helps clean up idle quality, etc.

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If the primary pipe inside diameter is more than 1/8" larger than the actual port opening in the head, the header flange bolt pattern can be slotted slightly to raise the centerline of the primary pipe above the center of the port, until the bottom of the pipe just matches.

This puts the pipe's effective center closer to the most active area of gas flow, and the mis-alignment at the roof allows the highest-pressure gas an easier path away from the port; also adds some degree of anti-reversion.
If controlling reversion is more important than maximum port flow (e.g. primary diameter is very large), Vizard suggests the mis-match should be at the bottom of the port where gas flow is slowest, and therefore most likely to reverse-flow at low engine speed.

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An easy way to effect a small increase in exhaust efficiency, if space permits, is to move the header out away from the port by 1/2" or more (using an extra gasket and longer studs or bolts).
This moves the restrictive angle farther away from the port - every little bit helps here. It also reduces local exhaust port temperature in the head slightly.
An easy spacer is an extra header flange or 2, but be sure that the transition from the extra flange to the header is not restricted.

The extra flange may be slightly larger than the port opening in the head, but must not step down entering the header. Do not taper, blend, or bevel the extra flange to act as a transition between the port and the header.

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Anti-Reversion Plate

If the header in use is substantially larger than other available choices for the same motor (i.e., you're using 2" OD, but headers are also available in 1-5/8", etc.), an inexpensive anti-reversion plate can be made from a bare flange with the smaller size (1-5/8"). Do these steps in order:
» Match the extra flange openings to the exhaust ports.
» Lay it over your actual 2" header flange.

» Spray paint, mark etc. the 2" openings around the 1-5/8" openings (they will
be concentric circles).
» Remove the marked area as shown, using ball end carbide, etc.

I would suggest the following rules for best effect:

» The extra, smaller flange be no smaller than your motor's exhaust port.
» The extra flange be at least 1/4" smaller than the header in use (if using a header with 2" primaries, the extra flange should be 1-3/4" maximum).
» Make sure there's enough room to move both sides of the header away
from the motor by 3/8" or so (the header flange thickness).
» You may need an extra gasket between the flanges, or sealer may do
» Longer bolts or studs will probably be needed; remember to use sealant on B/RB motors due to water in holes.

Header is useless if it's design did not properly place the O2 sensors at a distance and temp they were designed for as it will cause the sensors to incorrectly dictate to PCM on fuel needs.

Wiring extensions for 02s are bogus as the 02 requires an outside air source for reference so there is a special air channel between the wire and insulation so adding some wiring extension prevents proper colder outside air getting to the 02.

[Mr_Draco]

Originally Posted by brAnd7onX

SLP I believe only offers the 1 3/4's headers and the more popular ones like ARH and Kooks offers 1 7/8's. I guess I just wanted to know is there really any power difference between the two or even any sound difference? Thanks.

ARH recommends 1 7/8. In another thread they said they have dynoed several cars using both their 1 3/4 and 1 7/8 headers and that that the 1 7/8 had a larger increase in HP while there was no difference in torque on the Camaro.

[Anthony@ARH]

Originally Posted by Mr_Draco

ARH recommends 1 7/8. In another thread they said they have dynoed several cars using both their 1 3/4 and 1 7/8 headers and that that the 1 7/8 had a larger increase in HP while there was no difference in torque on the Camaro.

That is correct thanks for posting that up!

[Mr_Draco]

Originally Posted by Anthony@ARH

That is correct thanks for posting that up!

No problem

[Russell James]

Originally Posted by Mr_Draco

ARH recommends 1 7/8. In another thread they said they have dynoed several cars using both their 1 3/4 and 1 7/8 headers and that that the 1 7/8 had a larger increase in HP while there was no difference in torque on the Camaro.

Even in low and mid range torque? I can understand the higher hp at top end, but I would have thought that would be with a little low end tq loss. Maybe the catback was providing the same back pressure.

When I was messing with 5.3's in trucks they were real sensitive to header size and exhaust having some backpressure. Big long tubes and straight thru true duals on a stock truck would kill the low end SOP torque feel. Maybe the LS3 with the bigger port heads and more cubes likes the bigger headers?

[tjbusa]

Obviously 1 3/4 and 1 7/8 war can not be won comparing same brands. This is a quote from SLP.

"Best of all, we performed a heads-up test against the self proclaimed "Best 1-7/8" 4-into-1 Long-Tube Header on the Market" and guess what, SLP landed on top with both power and torque, not to mention ease of installation. We guarantee this to be the best Z06 header on the market. SLP's headers are second to none for your 2006-'09 Z06!

http://www.slponline.com/view_product.asp?P=30126


Now I realize this is a ZO6, but if its good for a ZO6, its good for my Camaro.

[Anthony@ARH]

Originally Posted by Russell James

Even in low and mid range torque? I can understand the higher hp at top end, but I would have thought that would be with a little low end tq loss. Maybe the catback was providing the same back pressure.

When I was messing with 5.3's in trucks they were real sensitive to header size and exhaust having some backpressure. Big long tubes and straight thru true duals on a stock truck would kill the low end SOP torque feel. Maybe the LS3 with the bigger port heads and more cubes likes the bigger headers?

From my back to back testing on the same car. There was no loss down low and I would agree with the more cube and bigger ports like the larger headers.

[1stGM]

Does ARH make an 1 3/4" header for the 2010 Camaro.....

[1320junkie]

Originally Posted by tjbusa

Obviously 1 3/4 and 1 7/8 war can not be won comparing same brands. This is a quote from SLP.

"Best of all, we performed a heads-up test against the self proclaimed "Best 1-7/8" 4-into-1 Long-Tube Header on the Market" and guess what, SLP landed on top with both power and torque, not to mention ease of installation. We guarantee this to be the best Z06 header on the market. SLP's headers are second to none for your 2006-'09 Z06!

http://www.slponline.com/view_product.asp?P=30126


Now I realize this is a ZO6, but if its good for a ZO6, its good for my Camaro.

hmmm from my personal experience and tons of Vette tuners...SLP is not the best header for a Z06..but it was their test and their product so I would not expect them to say another brand was better

[mwt18]

Originally Posted by Mr_Draco

ARH recommends 1 7/8. In another thread they said they have dynoed several cars using both their 1 3/4 and 1 7/8 headers and that that the 1 7/8 had a larger increase in HP while there was no difference in torque on the Camaro.

How can this be? HP is calculated from torque, i.e. HP=Torque x RPM (x 1/5252). So, if torque remains constant, the only way to increase HP is to increase RPM.