Why less power with sidepipes?

[Joe C.]

Re: Why less power with sidepipes?

Here are all of the U.S. manufacturers of Corvette side pipe mufflers/inserts#:

http://www.allencorvetteexhaustsystems.com

http://www.spiralturbobaffles.com/ (I recommend these for BBC only, using Hooker sidepipes)

http://www.classicchambered.com/index.html

http://www.stainlessworks.net/cart/index.php

http://www.sweet-thunder.com/

If you find anybody who makes a muffler that will attenuate as well as a N11 setup, or a Walker DynoMax while also presenting minimal flow restriction, then let me know.

Maybe you can invent one by using wave cancellation theory, by directing 180 degree phased waves back at the outlets. Really. Patent them.

Short of that, I recommend that you take a good look at the Classic Chambered website. One of their offerings is by far, the best you'll be able to do with sidepipes. If you fabricate a side exhaust system using those, along with a large diameter, short crossover pipe, close to the header collectors (or manifold exits), I believe that you'll be very happy with the results.

PS: I was very instrumental in giving the manufacturer the idea of fabricating and marketing this system. Watch and listen to the video clips.

#: All of these will fit under stock 1965-67 sidepipe covers, except those with a 3 1/2" outer shell, which may require a 1/2" spacer. Wrapping those with 3" and 3 1/2" outer shells in a thermal blanket is recommended.

[Roger P.]

Re: Why less power with sidepipes?

Duke and Steve,
Thank you both for responding to my gas mileage question. Duke, before you leave me on my own, I guess you need some additional information so you don't think that my car is a mechanical mess. My original engine (327/300) is out of the car on an engine stand as one of the previous owners put in a new GM Performance ZZZ crate engine (350/345) because he wanted more HP. I spoke to all previous owners (other than #1), and this guy was a GM mechanic for 6 years and did a body-on in 1989. I will one day put the original motor back in the car, but for now, I have a motor with only 6,000 miles so I'll run & play until it checks out. Perhaps this information saves me from the "modified" engine category?? Does the 12 MPG sound reasonable now, or should I be expecting better?

Thanks,
Roger (50141)

Duke,
With the additional information that I provided on my engine, do you have any opinion about my 12 MPG fuel mileage? I was also wondering if I changed my fan blade to a new stainless steel blade (perhaps larger and/or with an extra blade), would that help my engine run a little cooler. If I cruise on the highway for an hour, the temperature reaches as high as 200 degrees. I understand that is within normal range, but I would like to have a little more "wiggle room" if possible. Your thoughts and advice are appreciated!

Thanks,
Roger (50141)

[Duke W.]

Re: Why less power with sidepipes?

The torque curve, fuel efficiency, and operating temperatures (assuming the cooling system design is adequate) are all about the spark and fuel maps being optimally suited to the engine configuration. Without knowing the fuel and spark maps and a ton of details about the cooling system, I can give no guidance.

Typically when you slap a one-size-fits all carburetor on a crate engine (and then there is the distributor from who knows where) you end up with a far from optimum setup for best average torque and lowest possible fuel consumption, and a poor spark advance map may cause high operating temperatures.

The OE SB aluminum radiator and clutch fan, both in good operating condition, should cool any reasonable SB configuration as long as the fuel and spark maps are somewhere near optimum for the engine configuration.

Duke

[Ralph S.]

Re: Why less power with sidepipes?

There is good info here also.

[Jim T.]

Re: Why less power with sidepipes?

Duke and Steve,
Thank you both for responding to my gas mileage question. Duke, before you leave me on my own, I guess you need some additional information so you don't think that my car is a mechanical mess. My original engine (327/300) is out of the car on an engine stand as one of the previous owners put in a new GM Performance ZZZ crate engine (350/345) because he wanted more HP. I spoke to all previous owners (other than #1), and this guy was a GM mechanic for 6 years and did a body-on in 1989. I will one day put the original motor back in the car, but for now, I have a motor with only 6,000 miles so I'll run & play until it checks out. Perhaps this information saves me from the "modified" engine category?? Does the 12 MPG sound reasonable now, or should I be expecting better?

Thanks,
Roger (50141)

First thought are you using the full time vacuum port from your carb to the vacuum advance canister? If you do not have full time vacuum as soon as you start your ZZ engine your city mileage will be less. I installed a ZZ1 crate engine in my 1970 Corvette in the early 90's. On my first highway trip I got 17 mpg. Have a Holley 650 double pumper installed on my ZZ1. Your ZZ engine came with a HEI ignition distributor, is it in your Corvette's engine now? The ZZ engines HEI distributors had vacuum advance and I am using mine.