Radical hypothesis: Stock Manifolds vs LT Headers
 

Going to throw this out there and let the sh1tstorm begin: What if the stock exhaust manifolds paired with cat deletes make the same or better power than long tube headers with no cats/high flow cats? I have read a ton of threads, watched countless dyno videos of 6th Gen Camaros on Youtube, and I have not seen solid proof that long tubes are significantly better than the stock manifolds, all else being equal. The average gain seems to be about 16 RWHP when switching from the stock manifold with cats to long tubes with no cats. (As an aside, the RotoFab seems to be good for about 10 RWHP in most cases.)
The thing that has led me to postulate this counterintuitive hypothesis is my experience with my own 6th Gen. with the the following mods my car put down 438 HP/ 442 TQ : Flex fuel kit/Soler Performance throttle body/Pray Performance ported stock intake manifold/stock manifolds/cats/exhaust. Chart #1.
Then I added a RotoFab Dry and New Era cat deletes. The car put down 464 HP/ 468 TQ. It gained 26 HP and 26 TQ. About 10 HP/10 TQ can be attributed to the RotoFab. Deleting the cats and installed what amounts to 3" straight pipes instead was good for about 16 HP/ 16 TQ-give or take. Chart #2
Next I got my hands on a Pray Ported MSD IM and installed it. After it was retuned, it made 479 HP/ 469 TQ. Happy days! Chart #3
Earlier this year I finally shelled out for the American Racing Headers long system-X-Pipe, no cats. Installed it. Took it to the dyno and it made less power, much less: 463 HP. Then I spent a great deal of time, money, and energy recovering the lost power. Replaced spark plugs, wires and even ignition coils. Took it to a tuner-got bad results. Got a refund. Paid Pray for a tune-I can't say enough good things about his tune. I will just say that his throttle maps are phenomenal. Off idle hesitation gone. Anyway, went back to the dyno and made 472 HP/471 TQ. Pulling out all of the stops the car still made 7 RWHP less with the headers and exhaust than it did with the stock manifolds and cat deletes. Chart #4. (ignore run file #21-that's the bad tune that I got a refund for.)
Feel free to destroy my theory. Bring your charts and graphs and expert opinions. Don't be shy. Call me crazy. Meanwhile, I am going to test my theory. I still have my stock manifolds and exhaust. Waiting on some cat deletes. After I pull the headers and put the stock manifolds back on, the car is going back to the dyno. I should have results sometime in May. Stay tuned.

for a bolt on only car, i won't disagree that headers do little to nothing with regard to peak power numbers. i feel that a 2" header had no choice but to carry power above 6k better. the only real world example i have is my car. we made several pulls with a stock msd intake manifold and every one of them carried peak power from 6k to ~6700 and slowly fell off after that.

i think as high rpm airflow increases the demand for headers does, as well. put a high ram on the car and i think you'll see a larger difference in peak numbers and especially the exhausts ability to maintain that power.

I believe they do show up on a drag strip 1.5mph min. Idk what’s going on

I absolutely agree with you. Even if headers do produce 10 hp more than cat deletes they aren't worth the money and installation pain in the ass.

THANK YOU! Finally!!!!

Brandan

I thought this was old news, especially with the Tri-Y stock manifolds. Headers are more a sound/supporting mod on the 6th Gen than it is some big power gain.

I would tend to agree with you, the OEM manifolds being the tri-y design are pretty good already. I have no desire to mess with any part of my exhaust besides maybe a secondary cat delete after warranty is over.

I've done the full on monster build in my LS1 camaro and I have no desire to do that again in my life, at least until I have a kid to teach and build something with.

While I wholeheartedly agree that headers are not worth the trouble on a stock or bolt-on only car, I'm surprised that you didn't pick up 10 - 15 whp. If you're staying bolt-on only, I'd reinstall the factory exhaust, cats and all. Besides, you're in Cali. Won't they give you the needle if they catch you running with catless headers?

My personal car went from 450rwhp with 95mm hi-ram/stock 95mm TB, flexfuel(E), and cat deletes to 474rwhp by adding only the 2” longtubes w/tune of course. This was all done in 5th gear on the same mustang dyno the car has been on since stock.

That made me LOL. It's almost true. Herr Newsome is a fascist dictator in the making.

Weren't they using the gas chamber out there?

-Geoff

Gas chamber cant pass Cali emissions, I think they may soon require Californians to install catalytic converters in their rectums so that they themselves as humans are emission compliant...

This thread could not have come at a better time. Literally everyday for the past week I have been trying to decide which way I wanted to go with headers... TSP, ARH, Kooks, 1-7/8, 2", coated etc... I think I will grab the MSD IM and be done with it (I like the look of the MSD compared to the LT2) as I already have a Tony Mamoto TB, GM CAI, Borla Atak axle back. Thanks OP for sharing.

IMO, there's a lot of pointless mods going on these days that are only snake oil, for example catch cans for otherwise stock motors.

Today's cars are really good and many times it's difficult to improve on them.

2" primary headers for our cars are just stupid and you lose power due to decreased exhaust gas velocity and therefore decreased scavenging effect. I've used the same simulation software to design manifolds that the pros use... The only reason to use such headers would be for a totally built non-street use motor making a lot more power at higher rpms vs stock.