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  #1 (permalink)  
Old 09-04-2016, 11:55 AM
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Default Question about rattle in CR sidepipe

My CR Cobra just developed a loud "rattle" that sounds like it's coming from the muffler part of the drivers side, sidepipe. It's hard to tell the exact origin given the loud nature of a running Cobra's exhaust. It sounds like a rattle (two pieces of metal banging on one another) at idle and changes sound somewhat as the RPMs go up. My guess is the sound change is because the side pipes have some shake at idle that smooths out with RPM. It's fairly loud at both idle and above.

I thought at first the sidepipe had developed an exhaust leak at the header to sidepipe flange but I've verified the gasket is still good there and bolts are tight. I thought the fat part of the sidepipe was just a glasspack, but is there some metal in it that could have become detached?

I've got about 40K miles on the car and externally the sidepipes still look great due to having them JetHot coated when new.

Has anyone had something similar happen to their CR Cobra? Any ideas? Has anyone cut open a CR sidepipe and know what's actually inside?

My inclination is to keep driving it and see if it goes away or gets worse. Good idea or bad?
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Old 09-04-2016, 08:13 PM
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I am guessing that you have the "old" style side pipes. The old styles pipes have two internal 1 inch pipes to help silence the car a bit. So from the header to the side pipe, there is a round plate with one, 1 inch inlet going to the first pipe... On the other side there is a plate that connects to the second 1 inch pipe.
I am guessing that one of the pipes has disconnected from the plate. Or the plate has separated from the pipe and the external housing of the side pipe.

The up side is when you replace the glass pack portion of the side pipe, you will free up ALLOT of HP.
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Old 09-05-2016, 06:25 AM
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I had a rattle coming from the side pipe and it was just the bolt that goes from the hanger to the frame had come loose.
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Old 09-05-2016, 08:03 AM
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After you have ruled out any external things causing the rattle, you most likely have a baffle loose inside your side pipe. I had the same problem, and someone on here told me to drill a small hole in a place that cannot be seen. Then use a stainless steel sheet metal screw to screw into the baffle and pull it tight to the side pipe.

I use about 1-1/2" to 2" stainless steel sheet metal screw. Likely a #12 screw. I started with a small bit that the screw could start into. I drilled into the side pipe from under the car. After drilling through the side pipe, I then drilled through the baffle. Then I changed to a bit big enough that the screw could slide through, and drilled the outer shell only. This allowed the screw to tighten into the baffle and pull it tight to the wall.

You may want to understand the design inside to know where to drill. I was able to see with a mirror and flashlight. A small camera would be even better.

The down side risk is if the screw ever backs out, it could go into a tire. However the rattle should come back before it backs out. Mine has been this way about 5 or 6 years now.

The only other solution is to cut the pipes open to fix it right, which will require striping and re-coating after welding it back together. That or just replace them. Either way, it will be costly. A couple screws for a couple bucks is worth a try.
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Old 09-05-2016, 08:11 AM
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If you have the older original pipes you might want to consider replacing them.
I got a set of Don's less restricted pipes and what a difference that made in
available power. A bit louder, but only when you got on it.
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Old 09-05-2016, 12:17 PM
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Default Thanks for helpful responses

Yes, old style sidepipes as they were purchased in 1992 or so. After putting up the first post, I decided to take the car for a drive to try to further diagnose the rattle. It's certainly sounds like a loose baffle with most of the noise coming in the RPM range from idle to 2,500. The rattle sounds like shaking a few ball bearings around in a tin can. Above 2,500 RPM the noise almost completely goes away until you lift the throttle and then it came back.

Well, after about 30 minutes of driving, I took a hard right hand turn and the rattle just went away. One second rattling away, the next just gone. I'm guessing the baffle somehow vibrated itself back into the hole it came out of or somehow broke loose on the other end as well. With my luck it's probably temporary and the rattle will most likely come back. I do like the new exhaust sound though as it's a bit more throaty now.

@olddog: I'm guessing the baffle you screwed down is in the middle of the muffler part of sidepipe. Can you give me a sense for where? Like how many inches behind the collector to muffler weld did you drill the hole for the screw? I just might have to try this workaround if the baffle starts rattling again.
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Old 09-05-2016, 01:13 PM
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C5GTO,
You may try taking your side pipe off and see if you can shake anything loose out of there. Maybe it blew out that's why its gone now. But best thing is to replace those mufflers to the less restrictive type, retune and enjoy a new car. 40-70 HP gain is not unrealistic. I recommend the Classic Chambered Exhaust mufflers.

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Old 09-06-2016, 08:50 PM
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lol, just had this happen. Found a screw missing underneath. Got another screw with proper size and resecured. No rattle.
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Old 09-08-2016, 07:58 AM
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Quote:
Originally Posted by C5GTO View Post
Has anyone cut open a CR sidepipe and know what's actually inside?

My inclination is to keep driving it and see if it goes away or gets worse. Good idea or bad?

Yes- Here's what's inside the original CR side pipe mufflers:




That is a picture of a WHOLE LOT of restriction, and of a lot of places where rust has probably eaten away one of the joints between the inner pieces- resulting in your rattle.

The good news is- You can live with it, for as long as you can live with it. As the rust dissolves the inner steel away, it will just get blown out the end of the exhaust pipe.

If the sound doesn't bug you too bad, then you could let it go until the inner corrosion finally eats through the outer casing, or until one of the inner pieces gets so bad that it completely breaks loose and starts bouncing around in there like a marble in a soup can.
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Old 09-09-2016, 01:10 PM
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Default Sidepipe muffler replacement questions

Firstly, thanks again for all the info and especially the pictures!

Secondly, here's my observations after commuting with the Cobra for a week now and doing no repairs per see on the pipe. The baffling in the drivers sidepipe has broken down to the point that the rattle is completely gone and the exhaust sound levels have gone up a lot, especially when accelerating hard. I haven't seen any large baffling parts come out so I'm guessing the now broken baffling parts are laying on the bottom inside of the muffler. The exhaust noise is bearable on open country roads but not really (for a daily driver anyway) on roads that have concrete barriers or curbs. The amount of sound that bounces back to the car for practical purposes is bordering on ear damage level. I do think I can feel a power difference (could be placebo effect from noise though) but I'm guessing I now have an imbalance between right and left cylinder banks because of back pressure differences.

So I'm now convinced I should do a muffler replacement and I now need to narrow down the choices to make. The car has a 5.0L Ford Motorsports "X302" crate motor with EFI. Ford advertises this motor as potentially making 340HP but I've never got that much from it, could be the overly restrictive CR sidepipes.

Questions:
1) Several people have recommended the Classic Chambered Cobrapack muffler. For the "packed with insulation" 2.5 inch version of these, how does the exhaust noise level compare with the original CR sidepipes? Is it a little bit louder or way louder?

2) For those who have used Classic Chambered Cobrapack muffler, did you stick to a 30" model (same length as original) or go with something a bit longer? Their website says the longer the quieter they are. If longer, does the 32" model look OK on a CR Cobra or too long?

3) Is Classic Chambered the best choice or are there others that should be considered. For example, others that might have low back pressure but might be quieter? I don't mind some noise but it's a daily driver and I do like to hear the stereo as well

4) After welding in replacement mufflers, were you able to have the sidepipes re-coated with a ceramic, high heat coating again? Did this require the previous coating be completely removed? I've got Jet-Hot on mine, it generally is in good shape but there's certainly a bunch of small rock pits closest to the front tires. If coating removed, was it via sandblast or manual?

5) After muffler replacement, did you need to "re-tune" the motor because of back pressure change. I've had my EFI computer calibrated on a dyno to get A/F ratio right. Will I need to have it re-calibrated because the lower back pressure could introduce a risk of an overly lean condition?

Lot's of questions...thanks in advance for any insights you can provide.
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Old 09-09-2016, 02:52 PM
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** EDIT - After typing out all the stuff below, I remembered that I still have my original Classic Roadster sidepipe mufflers taking up space out in my shed - If you want to return your car's sidepipes to exactly the way they used to sound and perform, then send me a Private Message, and I'll make you a KILLER deal on these **


If you want similar noise volume levels to what you had with the original CR mufflers, and also want to free up some Horsepower, Order a pair of Flowmaster Slimline sidepipe mufflers - These are the quietest, free flowing sidepipe mufflers you are going to find.

watch this vid for some sound clips:
[ame]https://www.youtube.com/watch?v=HlDiQkWNhIY[/ame]

The ClassicChambered Cobrapacks are glasspacks, but they utilize a proprietary inner baffle design which improves flow- But they still sound like a glasspack - They will be lower pitched than the CR mufflers were under part throttle (more bass, less treble), and even with fiberglass packing, they are going to scream loud (90dB+) under WOT (My original ClassicRoadster mufflers tested at 80dB under WOT conditions)

Regarding re-tuning your EFI... it's possible that the WOT speed density tables would need to be richened up a bit, but probably not. For part-throttle cruise and idle conditions, your O2 sensors will allow the computer to re-adjust itself.
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Old 09-09-2016, 06:30 PM
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Jones Exhaust also makes pretty much the same muffler as the Classic Chambered. They are available through Summit Racing. I put a set on my car and they seem to be fine.

If you weld in new mufflers, the remaining ceramic coating has to be stripped and and the sidepipes re-coated.

You may have to do a little carb re-tuning if you install new less restrictive mufflers. If you're going to the trouble and expense of cutting, welding and re-coating, you might as well put in some good low restriction mufflers.

Ted

http://www.jonesexhaust.com/products.cfm?ProductTOC=10
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Old 09-10-2016, 08:00 AM
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Quote:
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Jones Exhaust also makes pretty much the same muffler as the Classic Chambered. They are available through Summit Racing. I put a set on my car and they seem to be fine.

If you weld in new mufflers, the remaining ceramic coating has to be stripped and and the sidepipes re-coated.

You may have to do a little carb re-tuning if you install new less restrictive mufflers. If you're going to the trouble and expense of cutting, welding and re-coating, you might as well put in some good low restriction mufflers.

Ted
Agree- I'm also using 24 inch Jones mufflers on my converted sidepipes, but I didn't mention them because the original poster suggested that sound levels were a concern for him; and both the classic chambered cobrapacks, and the jones glasspacks are both pretty loud when you stand on the throttle.

But I totally agree that in terms of cost and performance gain, Jones glasspacks are the absolute best "bang for the buck" option available.

The correct 30 inch Jones muffler to use with a 302 EFI engine would be number A4530B, with a 2-1/4 inch core:

https://www.summitracing.com/parts/jex-a4530b
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Old 09-10-2016, 08:03 AM
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Quote:
Originally Posted by C5GTO View Post
Questions:
5) After muffler replacement, did you need to "re-tune" the motor because of back pressure change. I've had my EFI computer calibrated on a dyno to get A/F ratio right. Will I need to have it re-calibrated because the lower back pressure could introduce a risk of an overly lean condition?
If you have Mass flow EFI (has a mass meter in the intake piping) I doubt there will be any tuning changes needed. If it is speed density (MAP sensor) you may need some tuning. If it is alpha-n (uses throttle position only) it definately will need tuning.

Even Mass Flow has a Alpha-N type table that is used when the MAF fails. That table is also used during rapid throttle changes, when the MAF is not fast enough to give accurate data. It is not a precise control strategy. I do not think it will matter, but you may want to speak to someone more knowledgeable.
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Old 09-10-2016, 08:20 AM
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I'm 90% sure his crate engine uses a Ford EEC IV computer, which switches to pure open loop under WOT, so the base load tables might have to be tweaked just a little bit (if at all)

- But I agree that it is probably not going to be necessary.
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Last edited by moore_rb; 09-10-2016 at 08:22 AM.. Reason: typo
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Old 09-10-2016, 11:28 AM
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My Classis Chambered muffler change has a whole different tone compared to the original CR side pipes. Deeper bass which tickles my insides. I like it. The open end of the internal louvers points to the exit. My friends who all have small blocks compliment the sound of my car. I have a carbureted big block. It stays quiet until I ramp up the RPM's then it screams. I usually wear ear plugs when driving. No radio. Maybe not the best choice if you want quiet. Try under car exhaust with some performance mufflers so the noise is all behind you.

CR has a slightly longer pipe and 3" vs 3.5" dia. compared to most other Cobras which gives the CR a unique tone.

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Old 09-10-2016, 12:37 PM
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Yes, the car has an EEC IV EFI setup, larger mass air meter, large injectors and Edelbrock EFI intake manifold. I worry about lean conditions (maybe over worry) because it ran lean before I had it dyno tuned and re-calibrated. I think the intake and heads are capable of flowing plenty of air, once the exhaust side is no longer restricted, hopefully it will all balance out. I seem to recall the dyno had the engine putting out about 300HP after re-calibration.

After doing more research on the different mufflers mentioned (and some others), I'm leaning towards the Flowmaster Slimline sidepipe mufflers. It looks like I'd need to adapt from 3" collector to 3.5" opening/outlet to turnout but that just means a couple more welds per side.

Has anyone heard or experienced anything negative about the Flowmaster muffler?

It sounds like one positive is that they will be cooler to touch with the double siding. I've had my kids and one friend get a "snake bite", that's never fun.
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Old 10-05-2016, 01:09 PM
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Default Wow...omg...wow

I'll start with the punch line first. During the first test ride with new mufflers welded in, my first impression was WOW...OMG...WOW. If I had know this one single modification would result in so much more power, I'd have done it 20 years ago. The external look of the CR1 sidepipe gave no indication about how restrictive and poor that piece really was.

After cutting the pipe open, here's the source of the rattle:



The baffle plate ruptured and the resulting loose chunk of metal was floating around in the muffler until it lodged under the internal piping. The result was a straight through muffler that wasn't stopping much exhaust noise.

I did go with the Flowmaster Slimline sidepipe mufflers. Here's pics showing the installation process.



Hint: make sure the bandsaw is cutting straight before doing this. Also, measure carefully as there's no good way to hold the resulting pieces for secondary cuts.





Original CR1 muffler compared to the 30" Flowmaster after tacking in pipe size reducers. With reducers the 30" muffler grows to about 33.5" in length. The Flowmaster is also 4.5" diameter versus 4". This didn't turn out to be an issue at all.

After lots' of cutting, welding, and metal finishing, here's the resulting raw sidepipe after the first test drive.



With the old mufflers, the power dropped off considerably at about 5,500 RPM. With the new mufflers, power between 5,000 and 6,500 RPM was pucker worthy. I shifted at 6,500 even though the RPM was still climbing fast and there was no fall off in power.

After the test drive, I discovered this:




The blue/purple areas are the uncoated reducers that are mild steel. The mufflers are SS and didn't show any discoloration. The existing ceramic coat didn't show any damage either. The ceramic coat is rated at 1,500 degrees, so the pipes didn't get that hot. I don't know what temp leaves mild steel purple though.

My gut tells me the new amount of muffler flow is resulting in a lean condition at WOT. Especially given the discoloration present after the muffler. I only wound it up 3 times on the test drive so it got hot fast.

Question for you guys who know about the signs of a lean condition. Do you think this evidence is showing it? My conservative side says I should get the computer re-tuned. It would also be nice to understand the HP gain purely from muffler replacement.
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Old 10-07-2016, 07:47 AM
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Quote:
Originally Posted by C5GTO View Post

Question for you guys who know about the signs of a lean condition. Do you think this evidence is showing it? My conservative side says I should get the computer re-tuned. It would also be nice to understand the HP gain purely from muffler replacement.

I wouldn't necessarily use the blue coloration on the pipes as a sign that you are leaning out too much - mild steel alloys can begin bluing as low as 650 degrees F, and your exhaust gases are running nearly double that.

Still - If I were in your shoes, and if I had the funds, I'd probably be thinking the same way you are, and would be booking a session with my dyno-tuner...

I'd also pull the 4 corner plugs, and look for bright white insulators, glazing, or the little pepper flecks that might indicate detonation.

I knew you would love the performance gain. How about the sound and volume levels? Did they meet up with your expectations as well?
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Old 10-07-2016, 07:27 PM
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Retune for sure. Sounds like another happy non restricted side pipe story. I know I was happy with the results of my change over.


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