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Thanks, who is the manufacturer and where can I find them?
Speedway Motors sells these. I had to modify the diameter on the ones I bought. I installed them in a Model A I'm building for a woman. She wanted it quieted down and they definitely accomplished that, almost too quiet. Several places sell similar items.
If you intend to keep the side pipes but aren't opposed to modifying the exhaust, consider adapting the products of Spiral Turbo Specialties (website link below).
My track car with side pipes has to meet sound limits which vary by track. Some tracks, Laguna Seca most notably, have limits that even bone stock factory exhaust sometimes doesn't meet. My car, with STS inserts (and maybe one or two tricks of my own) meets the sound limits at Laguna. To put a fine point on that: At one Laguna Seca race with severe noise limits in force, I pulled back into our paddock spot and my bride, who was sitting right there, did not hear me approach.
So, the point is that you can make side pipes much quieter.
I'm glad to hear your testimonial on the STS. I went with ACP headers and STS baffles for my big block car that I'm currently building. Haven't been able to hear the system on the car yet, but was already concerned that I would have to put a secondary full exhaust system under the car with electronic cutouts to humor my wife
Black Tux - The engine in my NOM 65 396 Roadster 'was' a .060-over 454 with a fairly warm hydraulic flat tappet cam, 228/238 duration. When I first heard the seller back the Vette out of his garage, it wasn't the engine or cam that was making the obnoxious sounds, it was due to the pipes. Did you check out the older thread I started about side pipes, if you did you'd see the pics taken while looking in from the end, and notice the odd looking baffles or dimples, whatever they call them. I've made a lot of calls, emails, etc trying to find out who makes a decent set of pipes, which I'll be installing onto the 427 10.3 compression hyd roller cam engine I'm putting together now. Here's the pic of the (believed to be) Sweet Thunder pipes that were only my roadster for maybe 100 miles. They look new because they almost are but...the outside looks have nothing to do with the sound they produce.
Mike T - Prescott AZ
I was in the same boat. I had an 11:1 502ci with a big cam (can't recall exact specs at the moment but believe it was .25X/.25X duration .63X lift, and 112lsa) built that made 655hp so I needed to make sure it could breathe but didn't want to go completely deaf. I opted for ACP (formerly Stahl) headers and 3.5" ACP side pipes with STS baffles. I'm told that as long as I machine a 1/4" aluminum spacer bar I can also use the factory side pipe covers which was a requirement for me.
I've not heard it run yet, but am hoping to do so before the end of August. If you've got time to wait I'll be happy to send you video of my setup for reference if you'd be interested.
I know this will not help with the C2 side pipes, but I built a set of side pipes for my '59. I made the spiral baffles from stainless steel inside 3" pipes. They are easily removable so I can "tune" the noise level if needed. The spiral baffles do quiet it down.
I'm glad to hear your testimonial on the STS. I went with ACP headers and STS baffles for my big block car that I'm currently building. Haven't been able to hear the system on the car yet, but was already concerned that I would have to put a secondary full exhaust system under the car with electronic cutouts to humor my wife
When I discovered my vintage racer would have to meet noise limitations at most of the tracks I enjoyed, I tried every aftermarket gimmick available. The only product which produced a meaningful reduction in sound level was the STS baffles.
They didn't seem to hurt performance at all, so I permanently installed them in my side pipes.
For events with truly severe noise limitations, I add the Speedway Motors baffles Robert61 mentioned. These were in the side pipes on that occasion when I managed to sneak back to our paddock space without my bride noticing.
I believe the Speedway Motors baffles actually do hurt performance but that's hard to quantify since at events with severe noise limits everyone has to restrict their exhaust. IOW, everyone slows down by about the same amount.
OP: The problem with sidepipes is their inability to effectively deal with the double exhaust pulses (8&4 and 5&7) at each side. Every engine revolution the exhaust pipes on your car suddenly see the equivalent of a 654 (327 x 2) cubic inch engine. Most of the common remedies to this noise problem are additional restrictions in the flow capacity of the mufflers.
I'm not a big fan of sidepipes, but I am a fan of reasonably quiet performance cars, and making the exhaust system as efficient as possible. This means making both sides of the system work 100% of the time, and not just be shiney ballast weight 50% of the time.
On every exhaust system I build (I'm too parsimonious to contract it out ) I install an H pipe crossover as far forward as possible (to balance out the pressure in both sides), and I also include some surge volume in the system to help absorb the double pulse exhaust mass/volume. Unless you're concerned about NCRS points, any muffler shop should be able to install a crossover pipe between the downpipes, and also package in some surge volume piping.
It's all just physics. I enjoy it, but it's not everyone's cup of tea.
Last edited by 69427; 06-18-2021 at 02:40 PM.
Reason: Added OP.
OP: The problem with sidepipes is their inability to effectively deal with the double exhaust pulses (8&4 and 5&7) at each side. Every engine revolution the exhaust pipes on your car suddenly see the equivalent of a 654 (327 x 2) cubic inch engine. Most of the common remedies to this noise problem are additional restrictions in the flow capacity of the mufflers.
I'm not a big fan of sidepipes, but I am a fan of reasonably quiet performance cars, and making the exhaust system as efficient as possible. This means making both sides of the system work 100% of the time, and not just be shiney ballast weight 50% of the time.
On every exhaust system I build (I'm too parsimonious to contract it out ) I install an H pipe crossover as far forward as possible (to balance out the pressure in both sides), and I also include some surge volume in the system to help absorb the double pulse exhaust mass/volume. Unless you're concerned about NCRS points, any muffler shop should be able to install a crossover pipe between the downpipes, and also package in some surge volume piping.
It's all just physics. I enjoy it, but it's not everyone's cup of tea.
This makes sense and thanks for breaking it down. My system does have a crossover, which is very close to the front. I am however, not sure I fully understand the "surge volume piping". Perhaps you can describe that for me a bit more?
I spoke with a person, who "knows Corvettes" about the excessive noise. He conditionally suggested "stuffing" the now hollow side pipes. Specifically, a combination/intervals of steel wool and wire mesh to hold in the contents. He is suggesting that this could very well decrease the decibel level. One one hand, it sounds plausible on the other hand it sounds waaaay too easy!?
Side pipes and loud are ALWAYS mutually inclusive. No exceptions - just various degrees of loud.
If in mentioning 2-1/2" side pipes is a reference to the inner core of the chambered muffler - that is not factory correct. Factory sidepipes were 1-7/8" diameter core and were fairly loud, somewhat mellow until rusted out, but also very HP restrictive. Inner core chambered pipes of 2-1/4", 2-1/2" and 3" are all after market and are generally arranged in increasing order of very loud to crazy loud. Different forms of chambered perforations and various packings affect overall noise some. If you want quieter and good power you can install an undercar exhaust system with stock mufflers and turn down tips and connect it to the side pipes with motorized valves so you can run it quiet or loud, depending on your mood. A cross over pipe can be added between the side pipes up near the bell housing which will make the sound deeper and mellower, but not necessarily quieter.
Wrong. Inside diameter of GM OE chambered sidepipes was 1-5/8" - I measured one right after it was cut off a customers' 66. See photo.
Wrong. Inside diameter of GM OE chambered sidepipes was 1-5/8" - I measured one right after it was cut off a customers' 66. See photo.
Small block and big block are 2 different inner diameters i was told when replacing mine.
The ones I just got from Classic for my LS3 65 are 3" ID transitioning down to 2.5" ID. A bit louder than I wanted but the spiral inserts are a good option for long trips.
Wrong. Inside diameter of GM OE chambered sidepipes was 1-5/8" - I measured one right after it was cut off a customers' 66. See photo.
I probably got my eights of an inch measurements mixed up in my memory, but the point is they had a small core and that was the only way GM made original side pipe mufflers. Any thing else is an aftermarket, custom reproduction.
Small block and big block are 2 different inner diameters i was told when replacing mine.
The ones I just got from Classic for my LS3 65 are 3" ID transitioning down to 2.5" ID. A bit louder than I wanted but the spiral inserts are a good option for long trips.
Aftermarket, you can buy about any size you want up to some that are pretty much a full contact fit to the outer covers with insulation removed. That helps the hp loss issue at the expense of being very loud.
I probably got my eights of an inch measurements mixed up in my memory, but the point is they had a small core and that was the only way GM made original side pipe mufflers. Any thing else is an aftermarket, custom reproduction.
I think you are correct and i was misinformed. All pipes had the same inside 1-3/4" and 2"&2.5" OD according to Willcox.
The od of the ones I bought from Eric at Classic are almost 4" but they still fit under stock covers without removing the insulation. They didn't come with any tabs/brackets so I have to have something fabricated to attach to the (aftermarket) frame.
It will probably quite It down if you can keep the contents from blowing back out but the performance will likely be like trying to take a crap with your fingers stuck up your butt.
Wait. You’re not supposed to stick your fingers up your butt? Maybe that’s why it takes me three hours to drop a load.
I think you are correct and i was misinformed. All pipes had the same inside 1-3/4" and 2"&2.5" OD according to Willcox.
The od of the ones I bought from Eric at Classic are almost 4" but they still fit under stock covers without removing the insulation. They didn't come with any tabs/brackets so I have to have something fabricated to attach to the (aftermarket) frame.
This makes sense and thanks for breaking it down. My system does have a crossover, which is very close to the front. I am however, not sure I fully understand the "surge volume piping". Perhaps you can describe that for me a bit more?
Thanks...
Surge volume is simply some additional pipe internal volume in the system to allow some of the exhaust mass to temporarily park to reduce the noise/pressure spikes (particularly the 8/4 and 5/7 large pulses). This can be an increase in the H pipe volume, or a larger diameter(or additional parallel tube) section of tubing on the downpipes, or if you wanted to go wild, a couple lengths of 2 1/2" pipe installed in the unused pass-through areas of the transmission crossmember (connected with flexible couplers to the downpipes).
It's kinda like putting capacitors on a noisey signal line. The capacitors absorb the spike energy when it happens, and then releases that energy after the spike is gone.
There is no such thing as quite sidepipes and no way to quite them down. To add to your misery if they are original GM pipes the 2 1/2” is the exhaust pipe size BEFORE it gets to the crimped section under the covers which turn into a 1 3/4” pipe size which is restricting your engines power.
06-18-2021, 09:27 AM
) I install an H pipe crossover as far forward as possible (to balance out the pressure in both sides), and I also include some surge volume in the system to help absorb the double pulse exhaust mass/volume. Unless you're concerned about NCRS points, any muffler shop should be able to install a crossover pipe between the downpipes, and also package in some surge volume piping.
