Can anyone help me with a few questions about my exhaust setup? I have an 85' Firebird/Carbed 383 Stroker/Doug's Long tube 1 3/4 headers/2.5" dual setup/Flowmaster Hushpower II mufflers/NO cats.
2.5" setup is running down pass side over ax and out back of car.
Problem 1:Installation of mufflers. The muffler shop could not fit these mufflers side by side, so they ended up putting one muffler in the stock cat area, and the other muffler in the stock muffler area in the rear of the car. I have never seen this done before. I was under the impression that they should be along side each other or one side would build up more pressure than the other.
Problem 2: NO X PIPE! Again the exhaust shop told me that they couldn't fit the x in. I would have settled for an H connector, but that wasn't done.

My exhaust pulses are off, almost likely building back pressure, and car sounds like a 60 impala with a 289. This should sound like thunder.
In any case I have to tweak this exhaust to get it right, possibly change the mufflers for the desired tone, and fix the offsetmuffler location.
I need some suggestions on how to do it right. I was thinking of running the duals to the back of the car into a dual in dual out X type muffler at the stock location. Any suggestions or criticisms??? I could really use the help...

 

I have a similar setup with 3" true duels and flowmasters, I can see where the fitment issues arrise, my floorpans have been rised where the rear seat was (no more rear seat) to fit the mufflers, I don't know about having the mufflers that far apart, was this a reputable shop, it seems like they should have called you or told you they couldn't do it the way you wanted. is this a street car racecar? if you don't want to raise your pans, I would check out the exhaust system pics

https://www.thirdgen.org/forums/exha...l-exhaust.html

 

Thanks, Eric. Yes reputable guy, and he did a great job on the system. I do wish he called me on this before going forward with the changes, but all in all I can't complain about the service, and he lowered the price because he couldn't do the X. Good guy.
I'm not looking to change the floor pan on the car all though I did think about it. I also referred to these exhaust pics before doing the job. The car is a 12-13 sec street/strip.
I spoke to a few people who suggested the "H" pipe first, then worry about the mufflers being far apart "If" its still a problem. I hate pulses. I'm looking for the exhaust to prrrrrr...

 

FWIW: I just finished doing a true-dual setup using the Dougs' long tubes into a modified Bassani true-dual "x-pipe" setup that runs to the back bumper. Ground clearance is improved over the 4" Mufflex I had before, and the sound is incredible if it wasn't for the chirp-grumble vibration of (I think) the headers contacting the subframe.

TA

 

Have you ever seen muffler in different positions, like I explained? Seem that it should create more or less back pressure the closer or further the mufflers are from the headers....??

 

well, basic exhaust theory says thats not right, esp without a balance pipe, the exhaust should be balanced, it's not necisiarily a back pressure issue, but more of reflected pressure wave issue. pressure waves are created inside the exhaust system which traval both forwards and backwords in an exhaust system. some of these pressure waves revert back into the combustion chamber and helps to scavenge (pull out) all of the exhaust gasses, when scavenging is optimized depends on when the wave is reflected back which depends on the distance between the port and the muffler (and many other variables primary tube size and length collector volume ect), so with the mufflers that far apart scavanging is optimized at different parts of the rpm band. this means that each cylinder bank has different flow, which causes imbalancen. we all know that imbalance is not wanted on any engine, I'm not really sure on how badly this would hurt performance, but I'm sure its not good.



have you considered an "X-pipe muffler"? I'm not sure how your exhaust is set, but you might be able to sneak one in and get a different exhaust not and an x pipe.

 

EricJohn is right on the money, by having dramatically different tuned lengths of pipe after your collector, you have "tuned" both sides of your engine dramatically differently, and an X pipe would help, but not solve the problem, as it would probably only be able to be put in after the first muffler.

In the clear light of day, our cars were never designed or intended to have true duals, so doing so will always be a compromise of some sort.

TA

 

Big help guys. I appreciate the input. Most likely i'll either move them together or change the muffler to dual in dual out solution, and the X Pipe is a must.

 

I dont see why you couldnt put the two mufflers in the stock location at the back of the car. You can weld the tips directley to the muffler. Thats the way my dad's 1980 corvette is. It has a 406 in it and sounds great.

 

That's true, the flowmaster hushpowers are real narrow, and I had a full sized series 40 back there when I had the single inlet dual outlet. I think the bend were a pain for the installer. Either that or he didn't think about it.. Could look like this...? Makes sense right? Any other Ideas???