Heavily Dented Headers/Performance Loss?
Tech Contributor
Joined: Dec 1999
Posts: 32,910
Likes: 2,402
From: Anthony TX
CI 6,7,8,9,11 Vet
St. Jude Donor '08
YES!!!!!!!! 
I watched this with heavy anticipation of a MASSIVE POWER LOSS! 
It just didn't happen.
I would have LOVED to see what the results would have been for a MILDLY MODDED engine or even a stock engine with just headers.
Things that make you go HMMMMMMMMMMMMM>
Thanks for posting
I watched this with heavy anticipation of a MASSIVE POWER LOSS! It just didn't happen.I would have LOVED to see what the results would have been for a MILDLY MODDED engine or even a stock engine with just headers.
Things that make you go HMMMMMMMMMMMMM>
Thanks for posting
Safety Car
Joined: Jul 2009
Posts: 3,755
Likes: 190
From: Baton Rouge LA
St. Jude Donor '14, '16
I really like all of the stuff on the motortrend channel. One thing I'm wondering is if these results would change if they ran it through an exhaust with any kind of backpressure.
Race Director
Joined: Sep 2007
Posts: 16,557
Likes: 2,106
From: Peoria/Phoenix AZ
C6 of Year Finalist (performance mods) 2019
The rest of the exhaust system is every bit as important as the headers. However, if the shape of the tubes had no importance, then neither would the diameter. The fact that their test had an increase in HP with mild restrictions, was also an indication the that tube size was initially too large for that particular application. If you noticed test A vs B, the RPM required to get a nearly identical HP was 500 higher, because the unbashed headers were not flowing well after 5800 RPM, due to too much area to fill and retain high velocity. Too big is just as much of a problem as being too small. The assumption they made, was that the headers they used were ideally sized for that engine and they were not.
Thread Starter
Racer
Joined: Dec 2015
Posts: 313
Likes: 27
From: DFW TEXAS
The rest of the exhaust system is every bit as important as the headers. However, if the shape of the tubes had no importance, then neither would the diameter. The fact that their test had an increase in HP with mild restrictions, was also an indication the that tube size was initially too large for that particular application. If you noticed test A vs B, the RPM required to get a nearly identical HP was 500 higher, because the unbashed headers were not flowing well after 5800 RPM, due to too much area to fill and retain high velocity. Too big is just as much of a problem as being too small. The assumption they made, was that the headers they used were ideally sized for that engine and they were not.
Welcome.
Corvette Stories
The Best of Corvette for Corvette Enthusiasts
150 hp to 1,250 hp: Every Corvette Generation Compared by the Specs That Matter
Joe Kucinski
8 Coolest Corvette Pace Cars (and Replicas) of All Time
Verdad Gallardo
Top 10 Corvette Engines RANKED by Peak Torque (70+ Years of Muscle!)
Joe Kucinski
Corvette ZR1X Will Be Pacing the Indy 500, And Could Probably Race, Too!
Verdad Gallardo
Top 10 Corvettes Coming to Mecum Indy 2026!
Brett Foote
Top 10 C9 Corvette MUST-HAVES to Fix These C8 Generation Flaws!
Michael S. Palmer
10 Revolutionary 'Corvette Firsts' Most People Don't Know
Joe Kucinski
5 Reasons to Upgrade to an LS6-Powered Corvette; 5 Reasons to Stay LT2
Michael S. Palmer
2027 Corvette vs The World: Every C8 vs Its Closest Competitor
Joe Kucinski
Race Director
Joined: Mar 2005
Posts: 11,549
Likes: 27
From: Southampton NJ
Those headers are for high end power. For example on our LS engines we have 3 sizes that I know of. 1 5/8" runners 1 3/4" runners and 1 7/8" runners. I selected 1 3/4" so I would keep low end TQ Those headers on the video could very well be designed for top end power. Basically just moving the power band from down low to up top.
Welcome.
Welcome.
Thread Starter
Racer
Joined: Dec 2015
Posts: 313
Likes: 27
From: DFW TEXAS
Once again thanks for posting. From that graph it does not look like power band moved but did gain.
Melting Slicks
Joined: Nov 2010
Posts: 2,625
Likes: 195
From: On the east coast we drive until we die
Unless I'm mistaken, Mr. Dennis lost torque with the 1 7/8".....?
Race Director
Joined: Mar 2005
Posts: 11,549
Likes: 27
From: Southampton NJ
Yep lost 20 RWTQ after maff adjusted and only gained 5 RWHP from 6800 rpm to 7200 really not enough to change to the 1 7/8" with that TQ loss on the drive home i could really feel the TQ loss, so didnt even run at the track swapped back to 1 3/4" I have most bolt ons and a serdi valve job stock valves cartek ported heads cartek cam 11.1 maybe 11.2 still 93 pump gas and an A4 373 gear with 3800 PA converter in a manual it would have easily dyno over 500RWHP and more RWTQ
