Original mufflers question for HP engines

[Virg464]

Have you ever driven it for a couple hours straight?

I guess I didn't really finish my thought: I can't hear any drone, or anything else for that matter. No, it's just a 1/4 mile car, can't imagine a long drive with that set up.

 

[33 IMP]

Seriously, I'd run the biggest walker quiet flow with 2 1/2 in/out, that will fit under the car. Should be very similar to the factory hemi muffler, size and sound.
But there is a solution for the drone. Google "helmholtz resonator for exhaust".

 

[33 IMP]

I guess I didn't really finish my thought: I can't hear any drone, or anything else for that matter. No, it's just a 1/4 mile car, can't imagine a long drive with that set up.

I ran a couple glasspacks as header mufflers on my 57chevy, many MANY years ago! But I couldn't call em glasspcks, ALL the glass was blown out. About 95% sound level of uncorked, they would ring like a bell if you hit em with a wrench.
But, I did have a set of very quiet triple pass that I could swap to, when I got tired of it..... or got "stopped".....

 

[Bird 426]

If you get quiet flows, it will cut into your performance. I just removed mine from my stroker Dart. Otherwise, they are quiet.

 

[gtxrt]

If you get quiet flows, it will cut into your performance. I just removed mine from my stroker Dart. Otherwise, they are quiet.

how much did it hurt performance ? what size motor ?

 

[Mariposa Mike]

I came across contact info today made by the PO when he checked out Walker. So it's possible that is what is on the car. Wish I knew for sure but I might be getting good info this week on the aforementioned Accurate product.

 

[Bird 426]

All that I can say is that the performance was noticeable. 418 stroker, Sixpack.

 

[Some Car Guy]

Problem with accurate is the shipping costs. They didn’t mention making a 2.5 in and out when I was talking with them, or they might’ve been the winner. I’d be interested if they mean just swelling the pipe end or if it would be an internal upgrade too. Kinda pointless to have small internals.

What I just did about six weeks ago was the largest dynomax super turbos in 2.5 with a can style resonator from Vibrant by the tank. X pipe too. I have zero drone from a full 2.5 system on a 69 GTX.

What I did get from accurate was the factory hanger in 2.5. Made it all fit really nice and I don’t have any buzzing interior parts either. Quietest, best system I’ve ever had.

Getting the mufflers and resonators from summit saved beau coup bucks over pretty much anything else.

Biggest trick was having the same exhaust guy for a quarter century so he did it all up perfectly and took time to carefully plan angles and even extend the driver side hanger a bit.

 

[AR67GTX]

I want to say that someone posted recently that Year One sells some Accurate exhaust products. But they don’t advertise them as such so you have to inquire. I think their shipping is a little cheaper compared to Accurate.

 

[gtxrt]

always ran the large dynomax super but they would drone even with the H-pipe. maybe the H-pipe made it drone. never really liked the sound it was like they had a hole in the muffler. on a street car I will give up 5-10 HP. I would think that HP loss would be after 4000-5000 rpms only and not down low. for performance with some nice sound but not too loud the borla xs mufflers were the best for me.

 

[Some Car Guy]

always ran the large dynomax super but they would drone even with the H-pipe. maybe the H-pipe made it drone. never really liked the sound it was like they had a hole in the muffler. on a street car I will give up 5-10 HP. I would think that HP loss would be after 4000-5000 rpms only and not down low. for performance with some nice sound but not too loud the borla xs mufflers were the best for me.

I had a 383 road runner with the super turbos and it droned badly at like 2200. Had h pipe, headers, and the one thing else that could’ve done something was it had a blocked heat riser. Wish I’d tried resonators back then just to know if it would’ve solved it. Really annoying deal. That’s why I went to this setup to avoid it. Glad it worked.

 

[gtxrt]

I had a 383 road runner with the super turbos and it droned badly at like 2200. Had h pipe, headers, and the one thing else that could’ve done something was it had a blocked heat riser. Wish I’d tried resonators back then just to know if it would’ve solved it. Really annoying deal. That’s why I went to this setup to avoid it. Glad it worked.

yes right around 2200 rpms or so

 

[Mariposa Mike]

Also agree on the rpms. 2000-2200. Accelerating it diminishes or coasting the drone goes away. I'm going to be driving to a car meet in one month. The drive will be about 120 miles one way. Probably be wearing ear plugs.

 

[Don Frelier]

If you still have the original 383 with log manifolds all the talk about a performance hit is unneccessary.
When I first got mine I had the 2" mufllers, 2" pipes, log manifolds and completely original engine which ran really well.
I really don't believe putting performance mufflers and 2 -1/2" pipes would have done anything to boost performance.

I did change to 68-69 manifolds a years later but the engine was rebuilt with 906 heads and a different cam at the same time.

I've changed quite a few mufflers over the years just with the car on jackstands.
Used to do it without any power tools.
Some required a lot of work, but I'm pretty stubborn.

But with a sawzall, ball pean hammer, air chisel etc... it's pretty easy.
Especially if the case where the new one has a longer case, just saw off the existing mufflers right at the end of the case.
First beat it up with a good sized ball pean hammer to stretch the pipe stubs coming out of the case.
Then cut a small groove in the muffler pipe stub and peel it off the exhaust pipe with a chisel.
It's not that difficult to remove the pipes from the manifolds either.

 

[Mariposa Mike]

Got the car on a lift this morning and on the passenger side muffler (of course not the one I looked at when crawling under the driver side for measurements) under the dirt/rust I found Dynamax 17748. Looked at their site and it lists as a Super Turbo 2.5" centered and offset. Took some pictures of the system but probably not necessary to post as we now know what is on the car. So if these are the problem, as Some Car Guy and GTXRT posted, then I would like to replace them with something w/o the drone. On this Charger there doesn't look like a lot of room to add a resonator and keep these mufflers. Maybe the easiest solution is to just replace the mufflers. The installer used some really nice Y bracket hangers and welded pipe supports to level the rear pipes out the back. Turned down tips as original. The H pipe is also a slip joint rather than being welded so that probably made the adjusting easier.

I took some course steel wool to the build up on the pipes and it does not appear to have rusted through. Later I will clean that up better and coat it with some hi-temp galvanized paint. This crud almost looks like undercoating but it is rusty when sanding it. Also scraped some of the same crud off the rear shock and found numbers 739131 and C-073 with Made In America. No brand but nice to see something not stamped China.

 

[Some Car Guy]

I’ve never had an early charger. Do they really not have room beside the tank? We’re talking like only 4 inches wide for the cans I used.

It’s worth checking as the bigger super turbos tested the best on that chart that is floating around. A member on here made it and flowed it against a pipe the same size. Others were many percent down against the supers.

 

[gtxrt]

the borla xs pro will out flow the big super turbo mufflers they are shorter too.

 

[Daniel Brunner]

If I remember right they used Walker/Thursh mufflers from the factory.
Dynomax mufflers are now the old Walkers. Ordered Dyno‘s too last week but not installed yet I heared they are quiet at idle and get loud about 5000rpm

 

[Mariposa Mike]

Attaching a picture I snapped yesterday. It's pretty tight back there. 4 inch wide resonators might work but the length would be an issue too. As for general room in this B body, when I purchased the car it was in need of new spark plugs and I can honestly say these are the worst I personally have ever had to change. Had to get all but one from under the car. The exhaust manifolds are really tight against the firewall and then you have the power accessories in the way on the driver side (this car has A/C, P/S,P/B) and the alternator, windshield wash reservoir, trans dipstick on the passenger side and very little firewall room with the log manifolds on either side. With the spare tire in the trunk well and the gas tank it's pretty tight. Could I make it work? Maybe. But a muffler exchange might be the easier way.

 

[33 IMP]

What size is the pipe in front of the mufflers? You might try a pair of glass packs in front of the mufflers, as resonators.
But I think I would agree, a different muffler might be a better solution, and probably about the same money as adding resonators.
Me? I might see if I could find some cheap scraps at a muffler shop and fashion some heimholtz resonators as an experiment.