Header insert killing power

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MoparDave

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Bought a demon few weeks ago with a pretty healthy 416. Car ran a best of 11.40 but seemed sluggish and slow to Rev to me compared to a very similar 408 I have with less cam in another car. Long story short had to change Trans and when pulled exhaust apart found these. Obviously removed them now car feels like it should rips to 6500 shift. Why would someone install these,
20220416_114426.jpg
and any guess on et without?
 
It has 3" with Flowmaster dumping at rear. Thought car was very quiet for3"
 
just noticed this is your first post, how bout some pics of the demon?
 
I use those mufflers. You have to increase the collector size to use them and have them work. If your header has a 3 inch collector you need a 3.5 inch collector with those mufflers.

You also need to test. I doubt your collectors are anywhere near long enough. You can add 20 inches of collector onto what you have and go quicker and faster than just open collectors.
 
Kinda odd they had those and full exhaust, I'm guessing they were trying to really quiet the car down.
 
My friend Charles has a 29 Model A with an old school 392 Hemi. He runs those type inserts with a turnout on them on the street. He ran it at the strip a while back and when he pulled the inserts out, the car went a solid .5 quicker. Yeah a HALF a second.
 
Like both your Demons, but the black one? WOW, just stunning!
 
That doesn’t look like it would do anything good for engine output....... but it would make for a fun dyno test.

7EB82F83-6070-4B05-8413-B1E5CEF10860.jpeg
 
That doesn’t look like it would do anything good for engine output....... but it would make for a fun dyno test.

View attachment 1715913539
Would be interesting, I can say big difference in the sound and performance. With them in, it felt like forever to pull 6000 rpm in 1st. Now rips to 6500 plus with ease.
 
Bought a demon few weeks ago with a pretty healthy 416. Car ran a best of 11.40 but seemed sluggish and slow to Rev to me compared to a very similar 408 I have with less cam in another car. Long story short had to change Trans and when pulled exhaust apart found these. Obviously removed them now car feels like it should rips to 6500 shift. Why would someone install these,View attachment 1715910911 and any guess on et without?
That Looks like Car Chemistry stuff
 
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