I just got a 2020 Challenger R/T Scat Pack 6.4L 392 and I want to put 3 inch headers and a 3 inch into 3 1/2 inch exhaust on it with a tune. Are my internal‘s gonna be OK?
Internals? I assume you're referring to your engine? If so, rest assured doing your proposed exhaust work will have no effect on your engine. Just a suggestion though; don't waste your money on the proposed mods. 1. Your car came from the factory with shortie headers. 2. Most of your factory exhaust is more than big enough for your engine's output. Matter of fact, too much increased flow will hurt your bottom-end torque basically making your car SLOWER at low to mid throttle.
1st, guessing you just typo'ed it, but you have a 6.4L not a 7.4L 426ci, is 6.98L or close basically 7.0L 7.4L would be 451ci 2nd, as Katshot said, the factory shorties will work much better for you on the street for low and mid range power. Yes, it will change the SOUND, but mess up what the Engineers at Mother Mopar have already figured out. I would just do the Resonator Delete or a good Cat Back system.
Stay with your shorty headers. They are more practical for the street. Long tube headers would only be beneficial for your top end speed at the track. Read this article about headers: Exhaust Headers | Dodge Challenger Forum
Everybody makes the mistake of thinking the muffler is in front of the resonator on these exhaust systems. just in front of the end tips, that unit is your muffler and the resonator is upstream from that. it was the same with the '70 and later challengers. i don't know why the engineers did it but they did. if you replace the muffler with something else get a good tune. Sean at HEMI FEVER did a great job for me at a very reasonable price. I've heard of jay greene, he is expensive. get the diablo sport tuner from diablo sport first. GOOD LUCK!
On the older automatics, like my 2009 SRT, the large "suitcase" muffler was in front of the rear resonators.
Thank Dodge for the confusion. At one point the "suitcase" was actually a combined muffler and resonator. For a time, the resonators were in front and the Miller's were out back, then in recent years they swapped position. Recently, I read that modern cars with modulated displacement don't actually have resonators. Instead the rear components are mufflers specifically tuned for the 4 cylinder pulses. At one point, I tried researching the issue but quickly gave up due to a lack of credible reference material. So, until we can find some credible answers I'm afraid we're left with internet "experts". IMO, this is a huge reason why Challenger owners face such an uphill battle when trying to modify their exhaust system.