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Expensive but you can put under car exhaust on in addition to the side pipes. You need electric cut outs and to completely switch from side to under you will need 4 cut outs. There is a member here that did it with two cut outs and it cut the sound somewhat. Do a search he has a video with sound of his car.
Install an H pipe between the two exhaust manifold downpipes. This will noticeably quiet the exhaust harshness due to the 8/4 and 5/7 double exhaust pulses.
I had a 1966 Corvette coupe a year ago and the side pipes were very loud. The owner somehow gutted them. I ordered two new quiet factory side pipes from Corvette America and that solve the problem
I had a 1966 Corvette coupe a year ago and the side pipes were very loud. The owner somehow gutted them. I ordered two new quiet factory side pipes from Corvette America and that solve the problem
I don't know how that would be possible? All those pipes are, are a 2 1/2 exhaust pipe that has crimps down the sides that effectively create a "baffled" pipe. If you cut the baffles out the pipes would be very flimsily and fall apart. Most likely he just put a piece of 2 1/2" exhaust pipe in in place of the original pipe making "straight pipes" out of it.
I don't know how that would be possible? All those pipes are, are a 2 1/2 exhaust pipe that has crimps down the sides that effectively create a "baffled" pipe. If you cut the baffles out the pipes would be very flimsily and fall apart. Most likely he just put a piece of 2 1/2" exhaust pipe in in place of the original pipe making "straight pipes" out of it.
There was a forum member (have to do a search) that replaced the side pipes with two round seamless glass packs welded together and they fit under the side pipe covers.
Install an H pipe between the two exhaust manifold downpipes. This will noticeably quiet the exhaust harshness due to the 8/4 and 5/7 double exhaust pulses.
I haven't personally done this but common sense and the experiences of others say this is probably the most effective way to mellow them out. Of course, if they are rotted out GM pipes or oversize replacements the improvement may be limited. Side pipes have a perforated core pipe that is inside the outer pipe and the outer pipe crimps center it, secure it and baffle the flow through the system. On the old GM pipes the perforated core would often rot out before the outside and baffling would be lost and harshness and noise levels would go up.
The repro pipes are crazy loud and do not sound like factory. I went down this road with my last 2 67's. I was very pleased with the NOS pipes I put on my 435 car. I had Allen's repro exhaust on my 400 car and it was quite loud, but didn't bother me (thanks to years of working in a machine shop).
I've never seen anything like that. I've had several side pipe cars but I've never seen those insides.
This is a picture I took of the inside of the OEM's off my car. This is with the headpipe cut off. The ID I measured is only 1 5/8" which is the basis of the theory that they choke the performance vs the out the back system.
This is a picture I took of the inside of the OEM's off my car. This is with the headpipe cut off. The ID I measured is only 1 5/8" which is the basis of the theory that they choke the performance vs the out the back system.
You can also look in the ends of the side pipe with a bright flashlight and small mirror and see the inner baffles.
08-13-2018, 07:13 PM
factory side pipes too loud
I haven't personally done this but common sense and the experiences of others say this is probably the most effective way to mellow them out. Of course, if they are rotted out GM pipes or oversize replacements the improvement may be limited. Side pipes have a perforated core pipe that is inside the outer pipe and the outer pipe crimps center it, secure it and baffle the flow through the system. On the old GM pipes the perforated core would often rot out before the outside and baffling would be lost and harshness and noise levels would go up. 
