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Hi all; I was wondering; seems every time I start with these words it leads to new parts; what is the perferred muffers and or headers for a 69 vert with a 390 engine. Need to do this as I had to drop exhaust and this is what happens when one thing leads to another. Thanks kevind:confused:
 

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Ahhhh, welcome to "while-I'm-at-it-itis!" Many of us fall prey to this deadly (well, at least wallet-draining) affliction.

First off, FEs are a PITA to fit headers (and I'm only going by a buddy's '69 428CJ Mach 1 with long-tubes, some 30 years ago)...

Secondly, 'preferred mufflers' leaves it wide open. Sound from the outside, sound (resonance) on the inside, performance, etc...?

Personally, with my 390+ inch motor (470-ish hp 393W), I like the DynoMax Super Turbo mufflers. I have shorty headers feeding a 2-1/2" H-pipe, back to the aforementioned 2-1/2" DynoMax Super Turbo mufflers, then 2-1/4" tails. Sounds great!!! No restriction either!!! Same ET/MPH whether 'uncorked' or through the mufflers.
 

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When selecting mufflers, I have three important factors to consider...compression ratio:cam selection, firing order:cylinder placement, and muffler placement.

Compression ratio:cam selection is a factor because they need to match...there is no muffler on the market that can make a wildly overcammed 8:1 engine sound good above 2,500 rpm. On the other end of the spectrum, an 11:1 engine with a .450" lift and 252 degree duration cam will sound horribly choked. There needs to be a happy medium for there to be the sound of "making power."

Firing order:cylinder placement comes into play for the simple fact that some engines just have "thee" sound, and don't need a lot of help. Take a 9.5:1 350 Chevy with a 292 duration, .510" lift cam, a set of 1 5/8" long tubes, 650 cfm carb, 2 1/2" full length exaust, and a set of Flowmaster 40 series mufflers placed 60 inches from the collectors. Then a 351W Ford with the same setup, factor in valve size being the same and no X-pipe, and you will notice a big difference in sound. The idles will seem almost identicle, but wrap those engines up and the Ford sounds like it's making power all the way up. The Chevy will begin to kackle. They may make the same horsepower, within a couple ponies, but the Ford's firing order:cylinder placement edges out the Chevy in the sound department. This is because the Chevy never fires two cylinders from the same bank in a row. The Windsor does, and this brings the exhaust tone together. Put in an X-pipe...and it's a wash. Then it's up to muffler placement.

Muffler placement is actually a huge factor. The more tube after the muffler, the more choked and weak the sound gets. You may get that tin can, throaty idle, which is cool, but it sounds like garbage with some throttle. I used to run header mufflers and no pipes...everything sounded awesome, except the lower rpm cruise...1800 rpm in 3rd gear destroyed my hearing. With chambered mufflers (Flowmaster/MAC), I like getting the mufflers as close to the rear as possible, with tailpipes as short as I can get by with. You can get by with a little more tailpipe, running straight through types (Thrush/Dynomax).

There are other factors like exhaust diameter, engine air flow, header type and size, and tubing bends. All in all, your engine combos dictate what exhaust sounds best. Your 390 does fire multiple cylinders from each bank in a row, so that's a big sound help. Give us a few specs and maybe we can get it narrowed.
 

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I am also looking to replace my headers, the ones that are on my 69 xr7 351 w. hit the bracket for the power steering cylinder. and the corner of the tork box
who has headers on there car that does not hit the under carriage.
 
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