1 3/4 vs 1/7/8 Long tubes

[BlaqWhole]

Originally Posted by Steve RS/SS

This is the off the article I originally saw when I made my decision for 1 3/4"-Chase posted the link again. I still think I made the correct decision for a stock engine. According to the article below I should pick up 30 hp

What Primary Diameter Should I Go With?

This is the area that seems to cause the most confusion but it is fairly straight forward. Header manufacturers usually offer two or three options when is comes to primary diameters for a specific vehicle. For example, for the Camaro SS most manufacturers are offering 1 3/4 inch, 1 7/8 inch, and 2 inch primaries. Below are some pretty typical numbers for what you can expect from traditional 4-into-1 long tube headers on an otherwise stock SS:


Stock: 370 RWHP 375 RWTQ
1 3/4 headers with high flow cats: 400 RWHP 405 RWTQ
1 7/8 headers with high flow cats: 410 RWHP 410 RWTQ
2 headers with high flow cats: 415 RWHP 410 RWTQ


As you can see, simply switching from the restrictive stock manifolds to 1 3/4 long tube headers is worth approximately 30 RWHP and 30 RWTQ on a bone stock Camaro SS. The larger the primary diameter gets the more air the headers will flow and the further up the RPM range the power band is moved. The more powerful the engine is the more beneficial it is to go with a larger diameter, especially when you introduce forced induction. This means that generally the more power you make or the more race oriented your application is the bigger primary diameter you need, the closer to stock or the more street oriented the smaller primary diameter you need.

The way I see it, there is no wrong choice with these three sizes because each of them will give you a significant amount more hp/tq than the OEM manifolds. However there are better choices depending on the person and their goal with the car. For me the 1-7/8ths were the better choice based on the price, possible fitment issues, and the numbers I wanted. For others the 2 inch are the better choice. As long as you're happy with your choice then I'm sure you made the correct one.

[JDP Sales]

We recommend 1-7/8" about 98% of the time. They are a great all around size for low and top end.

Best regards,

Tyler
888-308-6007

[axis]

Originally Posted by Steve RS/SS

This is the off the article I originally saw when I made my decision for 1 3/4"-Chase posted the link again. I still think I made the correct decision for a stock engine. According to the article below I should pick up 30 hp

What Primary Diameter Should I Go With?

This is the area that seems to cause the most confusion but it is fairly straight forward. Header manufacturers usually offer two or three options when is comes to primary diameters for a specific vehicle. For example, for the Camaro SS most manufacturers are offering 1 3/4 inch, 1 7/8 inch, and 2 inch primaries. Below are some pretty typical numbers for what you can expect from traditional 4-into-1 long tube headers on an otherwise stock SS:


Stock: 370 RWHP 375 RWTQ
1 3/4 headers with high flow cats: 400 RWHP 405 RWTQ
1 7/8 headers with high flow cats: 410 RWHP 410 RWTQ
2 headers with high flow cats: 415 RWHP 410 RWTQ


As you can see, simply switching from the restrictive stock manifolds to 1 3/4 long tube headers is worth approximately 30 RWHP and 30 RWTQ on a bone stock Camaro SS. The larger the primary diameter gets the more air the headers will flow and the further up the RPM range the power band is moved. The more powerful the engine is the more beneficial it is to go with a larger diameter, especially when you introduce forced induction. This means that generally the more power you make or the more race oriented your application is the bigger primary diameter you need, the closer to stock or the more street oriented the smaller primary diameter you need.

Those are peak numbers though. they don't show what's under the curve. There's only 1/8in difference between 1 3/4 and 1 7/8 so it's not like there's a HUGE difference. The Jannetty graph wasn't blown up enough to see what was really going on down low. They all looked bunched up but when you blow it up, you can see the little nuances.

[Apex Motorsports]

Originally Posted by Sales@JDP

We recommend 1-7/8" about 98% of the time. They are a great all around size for low and top end.

Same here.

[Bo White]

I've got 1 3/4 jba headers and weigh 100lbs more than a camaro but trap and et what camaros with 1 7/8 headers do locally.

[Steve RS/SS]

Originally Posted by Bo White

I've got 1 3/4 jba headers and weigh 100lbs more than a camaro but trap and et what camaros with 1 7/8 headers do locally.

Maybe it's me...I installed my headers and high flow cats today and it woke my car up and sounds like a beast. The worst part of the install was the heat....glad it's done

[Bo White]

My car went from 357rwhp to 411rwhp with 1 3/4" LTs and a Spectre intake and tune. My stock cat back is 2 1/4" unlike the Camaro 2 1/2.

[Surfrman]

But besides the size you must to tune the ecu? or that are normal gains with out tune?