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Old 03-19-2022, 10:45 PM
lugnutx2 lugnutx2 is offline
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Default I'm needing advice on exhaust for a 68 400 HO firebird

I need to replace the exhaust on a 68 400 HO firebird, and am looking at a couple systems that Ames sells. The first is, # FN389LW RA/HO transverse muffler with resonators and tips, I'm guessing that it's 2 1/4? The second is FNSGF70, 2.5 Xpipe with Race-Pro cross transverse muffler only. The third is FN389LT RA/HO transvers muffler, no resonators and for tips. Anybody using one of these on their bird? How was the fit and sound?

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Old 06-26-2022, 09:10 PM
389 389 is offline
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X pipe will ruin exhaust tone. Use a pair of Dynomax Super Turbos with the flow directors. Put a half quart of transmission fluid into each muffler and let it soak all night then flip it over the let it sit another night add a little more.
It will smoke for a few miles but after a few hundred miles you will love how it sounds. Perfect, deep low tone with a very slight crackle at idle with the vacuum advance removed and the initial timing raised to 18 or 20.. It will also run much better without that vacuum advance.

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Old 06-27-2022, 11:16 AM
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Jim Moshier Jim Moshier is offline
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Quote:
Originally Posted by 389 View Post
X pipe will ruin exhaust tone. Use a pair of Dynomax Super Turbos with the flow directors. Put a half quart of transmission fluid into each muffler and let it soak all night then flip it over the let it sit another night add a little more.
It will smoke for a few miles but after a few hundred miles you will love how it sounds. Perfect, deep low tone with a very slight crackle at idle with the vacuum advance removed and the initial timing raised to 18 or 20.. It will also run much better without that vacuum advance.
What is the transmission fluid for in the mufflers? to soak the damping material?

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Old 07-18-2022, 08:32 AM
mgarblik mgarblik is offline
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Not sure if this will help but I had a custom system built with Goulrich XLerator transverse muffler and no resonators. This was a stock 68 400 HO convertible. It was SUPER LOUD! So loud in fact, I was concerned about getting a ticket. I had small resonators added to the system and it quieted it down allot. I did not use a X or H pipe because since it was a convertible, there simply was no room with the chassis cross support bolted in right where those pipes would need to be.

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Old 07-18-2022, 10:21 AM
78w72 78w72 is offline
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X pipe will change the exhaust tone compared to straight pipes but it wont "ruin" it.

i have a pypes system with an X pipe & straight through race pro mufflers, it sounds great to me, especially at medium or full throttle acceleration, idle is nice too with a OF hyd roller cam... but most of all is there is little to no drone that i do get with my other car that has a smaller cam & a 2.5" crush bent system with H pipe flowmaster 40 mufflers.

for a street car, do NOT remove the vac advance.. it will not run "better"!

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Old 07-18-2022, 10:57 AM
JLMounce JLMounce is offline
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It's a bit more expensive, but I would look at the Magnaflow system with the transverse muffler if that's what you're after. I have a 2.5" Pypes system with X pipe and under floor mufflers. Originally I chose the Violator mufflers which were novel for a while, but ultimately I tired of them. They are overly loud and the way they are constructed, they act as a straight pipe when any amount of load is on the engine.

I recently replaced those mufflers with Magnaflow mufflers of the same size and for me, the sound is perfect. It's quiet at idle and when cruising around, even at highway speeds with RPM's around 3000. As soon as you get into the throttle, they reward you with a deep growl that maintains a smooth and even tone, changing in intensity as the rpms climb.

The Pypes mufflers are a bit tinny and blatty to my ear.

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Old 07-18-2022, 06:31 PM
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jwcfbd jwcfbd is offline
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I can't help with your choices but I went with Flow Master's kit 17104 with Hooker Super Comp headers.
My install. https://forums.maxperformanceinc.com...d.php?t=423873
https://youtu.be/XyMRq8ne_WQ

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