'69 BB Exhaust Replacement Question
Thread Starter
Pro
Joined: Jun 2004
Posts: 561
Likes: 1
From: No longer in Heaven
'69 BB Exhaust Replacement Question
I am replacing the under-car exhaust system (427/435) and am a bit confused about 2"-2.5"/replacement/high performance mufflers.
I want to use 2.5" pipes and would like as good performance as possible without crazy loudness.
The replacement mufflers in all the catalogs look like the inlet pipe is initially 2.5 inches, but appears to shrink down to 2" where it is integrated into the muffler. This looks very restrictive to me (why use 2.5" pipes if the thing gets squeezed into 2" at the muffler?).
Are there high performance mufflers that actually retain the 2.5" diameter into/through the muffler? Does it matter?
If there are some options out there please let me know and point me to the right place.
Thanks.
I want to use 2.5" pipes and would like as good performance as possible without crazy loudness.
The replacement mufflers in all the catalogs look like the inlet pipe is initially 2.5 inches, but appears to shrink down to 2" where it is integrated into the muffler. This looks very restrictive to me (why use 2.5" pipes if the thing gets squeezed into 2" at the muffler?).
Are there high performance mufflers that actually retain the 2.5" diameter into/through the muffler? Does it matter?
If there are some options out there please let me know and point me to the right place.
Thanks.
Melting Slicks
Joined: Oct 2002
Posts: 2,317
Likes: 111
From: St Louis MO
I agree that the replacement mufflers with the 2 inch outlet are more restrictive than the aftermarkets with 2 1/2 inlet and outlets. If you pick an aftermarket muffler, you will probably need to do some fabrication to make it work. 
Racer
Joined: Dec 2007
Posts: 315
Likes: 5
From: Sheboygan Wisconsin
Contact Mike Allen at Allen's Stainless Exhaust Systems. They make a true 2-1/2" muffler. I have one of his systems on my '74.
http://www.allencorvetteexhaustsystems.com/
http://www.allencorvetteexhaustsystems.com/
Melting Slicks
Joined: Dec 2006
Posts: 2,483
Likes: 1
From: Bay Area CA
I am in the process of installing a 2.5 inch system that I bought from corvette central.
I did not find out that their 'end to end 2.5 inch system' has mufflers with 2 inch outlets. However ridiculous it may sound, corvette central still sells them as their end to end 2.5 inch systems.
I don't mean to say that Magnaflow mufflers are bad. Magnaflow makes great mufflers and there are a few 2.5 inch universal fit mufflers that will fit a 69 corvette.
The best way to go is to get a good muffler shop bent mandrel bent pipes and hook them up with a pair of mangnaflow or dynomax mufflers with 2.5 inlet and outlets.
Allens is certainly a good option.
I did not find out that their 'end to end 2.5 inch system' has mufflers with 2 inch outlets. However ridiculous it may sound, corvette central still sells them as their end to end 2.5 inch systems.
I don't mean to say that Magnaflow mufflers are bad. Magnaflow makes great mufflers and there are a few 2.5 inch universal fit mufflers that will fit a 69 corvette.
The best way to go is to get a good muffler shop bent mandrel bent pipes and hook them up with a pair of mangnaflow or dynomax mufflers with 2.5 inlet and outlets.
Allens is certainly a good option.
Le Mans Master
Joined: Jul 2006
Posts: 8,117
Likes: 104
From: charlotte north carolina
i wonder what effect the cooling of the exhaust gases has on their real-life volume, and the restriction of a 2" muffler output pipe? maybe the generals engineers know more than we think.
Melting Slicks
Joined: Dec 2006
Posts: 2,483
Likes: 1
From: Bay Area CA
Strong argument there...
I guess the only way to find out is to do some dyno tests...
Team Owner
Joined: Jul 1999
Posts: 26,545
Likes: 46
From: Huntersville NC
The stock tips (and the stock replacement tips) for 68/69 start at 2" .
What my exhaust guy did for me is he cut off the 2" section of the exhaust tip (see the picture) and welded the remaining piece to the end of my muffler. It is a touch shorter than stock... which you don't really notice, but I retain the 2.5" diameter.
What my exhaust guy did for me is he cut off the 2" section of the exhaust tip (see the picture) and welded the remaining piece to the end of my muffler. It is a touch shorter than stock... which you don't really notice, but I retain the 2.5" diameter.
Melting Slicks
Joined: Dec 2006
Posts: 2,483
Likes: 1
From: Bay Area CA
The stock tips (and the stock replacement tips) for 68/69 start at 2" .
What my exhaust guy did for me is he cut off the 2" section of the exhaust tip (see the picture) and welded the remaining piece to the end of my muffler. It is a touch shorter than stock... which you don't really notice, but I retain the 2.5" diameter.
What my exhaust guy did for me is he cut off the 2" section of the exhaust tip (see the picture) and welded the remaining piece to the end of my muffler. It is a touch shorter than stock... which you don't really notice, but I retain the 2.5" diameter.
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Team Owner
Joined: Jul 1999
Posts: 26,545
Likes: 46
From: Huntersville NC
Team Owner
Joined: Jul 1999
Posts: 26,545
Likes: 46
From: Huntersville NC
Team Owner
Joined: Jan 2006
Posts: 37,637
Likes: 3,118
From: Crossville TN
I would agree that the temp reduction from engine to exhaust outlet would more than account for the size reduction. The 2.5" header pipe has gases at a few hundred degrees...outlet temps are less than half of that. 2" outlet pipes shouldn't cause a restriction problem.