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I am looking at purchasing a complete OEM style exhaust system for my '71 429cj vert. A couple questions come to mind:

1. 2 1/4" (factory) vs. upgrading to a 2 1/2" sized system. There has been some discussion in the past that the factory 2 1/4" was limiting the performance of the factory 429cj ie: Increasing the dia. of the exhaust would increase performance. I will be keeping the car completely stock otherwise... Thoughts?

2. Mufflers: What would be the best muffler for this application, keeping in mind that the car will be street driven occasionally and not wanting to upset the neighbours too much... As the car will sit for extended periods of time, is there one brand better then another re: internal damage from sitting?

I am looking at systems offered by a co. called precision exhaust out of Ashford, Conn. Anyone familiar with their systems? Seems like they do a lot of business with Mustangs... Thanks

 
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I went through this a few months ago I ended up going with a 2.5 from headers back to mufflers then 2.25 from mufflers back to tail pipes. This was to make it quieter and reduce the drone that's commonly associated with these cars. I went with Dynomax super turbos at the advice of members on the site. I might have given up a bit of performance for a more manageable sound but with a vert I didn't want it horribly loud. From what I've read if you keep your 429 stock I think the two and a quarter is OK. I think the wider you go the more noise. I thought I read somewhere that the two and a quarter will go up to 400 horsepower. See attached sound clip.

I look in precision and they said that I would need to add 1/2 inch spacers in the crossover plate(vert only) to use their exhaust which I wasn't willing to do. I ended up going custom.

http://s172.photobucket.com/user/jharness/library/?view=recent&page=1

 
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Sounds real good!

the issue of the spacers concerns me, not exactly sure where in the exhaust system on a vert these would be required if I purchased the exhaust system from this company. Can you explain in more detail for me. Thanks

 
Sounds real good!

the issue of the spacers concerns me, not exactly sure where in the exhaust system on a vert these would be required if I purchased the exhaust system from this company. Can you explain in more detail for me. Thanks
Click to expand...
So we vert guys have that tunnel crossover plate that adds support. The exhaust has to fish through it. When it called these guys they said thier system wouldn't work unless you added lowering spacers to lower the plate(I think they said they sell them). Might be different now or you might be able to get an exhuast shop to add more bend to their system. Maybe give them a call and see what they say.

 
I will discuss with them before making a decision. They should be able to sell a system that meets the needs of all body styles, given the differences between a vert. and other models. I also do not want a system that will be piece milled together... To make it fit... Thx.[/align]

 
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Whatever direction you take, I would think lowering the vert plate would just add to potential clearance issues. With a vert, that's the trickiest part to get right with 2 1/2" pipes.

With my 69 vert I could not fit the plate with my 2 1/2" system w/ X-pipe so I'm working on a alternative plan of tying the tunnel together at that point with an over the exhaust set-up.

_____

Sorta like this __/ O O \__ if you can picture the idea.

 
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Here's another option

http://www.7173mustangs.com/thread-aftermarket-torque-plate?pid=173935&highlight=plate#pid173935

Also you shouldn't have any problems but in two and a half inches tunnel. I did two and a half through the tunnel and I have an aftermarket aluminum driveshaft which is a half an inch wider than stock.
Click to expand...
That looks nice, something I will give strong consideration to before making a final decision. I will not look at altering the cross over plate, not original and I agree every 1/2" of clearance is all good...

I do have a question about the mufflers you chose: Can these come with the weld on brackets so that I can run the factory dual exhaust hangers? Thanks

 
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Here's another option

http://www.7173mustangs.com/thread-aftermarket-torque-plate?pid=173935&highlight=plate#pid173935

Also you shouldn't have any problems but in two and a half inches tunnel. I did two and a half through the tunnel and I have an aftermarket aluminum driveshaft which is a half an inch wider than stock.
Click to expand...
That looks nice, something I will give strong consideration to before making a final decision. I will not look at altering the cross over plate, not original and I agree every 1/2" of clearance is all good...

I do have a question about the mufflers you chose: Can these come with the weld on brackets so that I can run the factory dual exhaust hangers? Thanks
Click to expand...
I'm sure you can add the hangers. I actually bought the stock hangers and after consulting the exhaust shop decided to go with the set up that they had. It kept exhaust system more rigid. I ended up returning the stock hangers.

 
Magnaflow makes a 2.5" stainless system that is labeled as fitting 67-70 mustangs that a VMF member installed on his 123 vert and it fit without issue accept for adapting to his header collectors which any system will require. I think I posted pictures of it here a long time ago.

I made my own from 2.5" mandrel bends and welded it together and while tight it fits over the crossover plate.

There is a company that makes a custom crossover plate with a drop which provides extra room. I have posted about that previously as well.

I am supposed to be working right now or I would search and post the links:D

 
If you are still running the cast iron headers going larger with the exhaust pipe will probably make little or no performance gain.

I just took a Pypes 2.5" dual system off of the 72 vert parts car I have. It was two weeks old when it got crashed. They had put the spacer between the plate and floor on the vert to clear the Pypes system. 1/2" piece of box tubing between floor and plate. I don't have a pic in the car I do not think. The car sounded good with them not real loud. This was on a 351 H code 3 speed.

My 73 vert has Dynomax I believe and it is too loud for sure. Too loud if you want to talk to someone in a vert top up or down.

If you ever saw the Roadkill guys doing their experiments with exhaust headers on TV you might be surprised. They would beat on the tubes and close them up and it had zero affect on the HP on the dyno, lol. Had to be drastic to make a difference. Google it might be on youtube. They did same with air cleaners also.

Picture of the system I took off the vert, like I say brand new and ceramic coated headers but for 2-V heads. Took it off in one piece jacked the rear springs down to get over housing.







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