Poll: Whats More "Restrictive" - Sidepipes Or N11 for Midyears Whose Got The Evidence

[396 RAT]

Will post my dyno results comparing both down the road.
It isnt just at high rpm's. HP and Torque both suffer
throughout the rpm range. Wished it wasn't the case,
as I have a NOS set wrapped in plastic in the rafters.
John Z hit it on the head, there really is no debate here.

 

[John Mcgraw]

You know, a lot of the decision has to do with how you intend to use the car as well. I agonized over the decision of whether to put side exhaust on my current 65 resto-mod project, and finally decided to go for a quieter, under-car exhaust. The visual appeal of the side pipes is undeniable, but in my opinion,the sound of the sidepipes is aggravating on any trip over 20 miles.
You are always only hearing one side of the engine because it is so close to your ear, and to my ears, it never sounds what I would call mellow.

After 200 miles in the driver's seat with sidepipes, you are reday to go postal.
My buddy came over with his new 67 with side pipes on it a couple of weeks ago, and it did nothing but reinforce my decision to stick with under-the-car exhaust!

Regards, John McGraw

 

[stepinwolf]

it never sounds what I would call mellow.

After 200 miles in the driver's seat with side pipes, you are ready to go postal.
My buddy came over with his new 67 with side pipes on it a couple of weeks ago, and it did nothing but reinforce my decision to stick with under-the-car exhaust!

Regards, John McGraw

I completely agree with John, regarding the side pipe use, and my last four rides ( all side pipe cars ) will attest to that.

My next project, a 67 big block coupe, will have both systems installed. A beautiful set of side pipes with " original " GM mufflers, and a full under car exhaust system with quiet mufflers, that will not be seen, and will be controlled by a new set of electric cut-outs.

I figure I will have the killer looks and sound when needed, and the quiet peace of mind when it's time to put a little millage on the spinner.

Slightly non conventional, but it will work for me.

Stepinwolf

 

[ZRGator]

Will post my dyno results comparing both down the road.
It isnt just at high rpm's. HP and Torque both suffer
throughout the rpm range. Wished it wasn't the case,
as I have a NOS set wrapped in plastic in the rafters.
John Z hit it on the head, there really is no debate here.

396 RAT, if you'd ever consider selling those NOS chambers, I'd like to know about it. Thanks..

 

[Lucy64]

I have underbody chambered by Walker (the orig sidepipe mfr now available through Mid America) on my '65 roadster and it flat screams at WOT but is very nice and rumbly at low RPMs. BTW, it's 2 1/2 inches in dia all the way back to the tips...!

I have this same setup and it is just flat loud. I don't know what it is or isn't doing for power, but it is louder than any sidepipes I have ever seen with my new high compression smallblock. It does turn heads.

 

[Ken Anderson]

Yup, the (perforated) inner pipe is 1-7/8" diameter; I have an SAE Paper filed away somewhere written by an engineer at GM Research in the late 60's which stated (with lots of empirical dyno evidence) that the turbulence created by the pressure waves induced by the protrusions into the inner pipe reduced the flow of hot gases and created more backpressure than an ordinary non-perforated pipe of the same diameter.

I participated in a day-long "A-to-B" comparison on a '69 Camaro Z/28 with factory chambered exhaust which was being changed over to the standard factory conventional dual exhaust two years ago. Same car, same day, same chassis dyno, no changes to the car except swapping the exhaust system. Made three pulls with each system, and the standard factory dual system made 25-30 more peak rwhp than the factory chambered system did. Didn't have instrumentation to measure system backpressure differences, just the dyno numbers.

I'd expect the differential to be much higher for a big-block, as it's trying to pump 50% more air than the 302 in the Z/28.

Corvette sidepipes and Chevelle/Camaro chambered under-car systems were NOT engineering-inspired; they were Sales/Marketing-inspired, and generated LOTS of option profit and "street image".

Are you saying that off road side pipes for a big block produce less torque than the stock under car system?

 

[jims427400]

Stepinwolf,
in your last thread you said your fitting the next car w/(GM ORIGINAL)side pipes.Where do you buy such animals,and how much do they cost. I've got original(old)sidepipes that are very loud and have considered getting something less radical(i cant hardly hear what the engine sounds like) Jim

 

[JohnZ]

Are you saying that off road side pipes for a big block produce less torque than the stock under car system?

Yes, although I don't have any A-to-B comparison data to document it like I have for the Z/28 test. GM Research data showed that the factory 1-7/8" sidepipes have more resistance to flow (system backpressure) than the under-car system does, which reduces effective cylinder filling during valve overlap and increases reversion pulses at the exhaust valves. Sidepipes SOUND like mega-horsepower, but the under-car system is actually more free-flowing with less reversion and backpressure, and will produce more power and torque; how much, I don't know.

 

[66427-450]

maybe some day one of us with a stock engine will check it on the dyno and get some hard data....

however, i just talked to a stock 425HP drag racer last week....... he said the 2.5" core side pipes made a consistant 1.5 MPH difference in the 1/4 (over the original spec 1 7/8" core sidepipes).....you can do the math to determine the HP difference there.

Just another data point.

 

[lonestarvette64]

I've run both the undercar chambered and factory side pipes. As far as performance, I could tell no difference. I now run the factory sidepipes because no other exhaust system will EVER sound sweeter as factory sidepipes at 6000rpm!!!