Side Exhaust on a 67

[Duke W.]

Re: Side Exhaust on a 67

Ron,
I had my '65 fi engine run on the dyno with both sidepipes and the dyno exhaust. The sidepipes cost over 30 horsepower.

George

This information is too sketchy to draw conclusions. How about some details?

Lab dyno or chassis dyno? What type of correction?

Describe "dyno exhaust" in detail. Headers? Primary length and OD? Collector and tail pipe lengths and ODs? mufflers? Where in the system were they located?

Same for when the side pipes were tested - complete unambiguous detailed description of the exhaust system from the exhaust ports to the atmosphere exit?

Were there any other differences in the configuration other than the exhaust systems?

Duke

[George C.]

Re: Side Exhaust on a 67

Ron,
It's a tough decision. Here is my OPINION, I have a 65 convertible with a 327/365 and 4 speed. The side pipes on it were GM parts, but not factory original.
I took them off because as others have said the highway drone was annoying, and honestly I think the car looks better without them, I'll probably be shot for that comment. They are also hot even with the shields on if you wear shorts in the summer.
About performance, it is a huge difference, I mean a difference you can feel, I didn't have it dyno-tested, but it is a noticeable improvement with the 2.5 inch under car exhaust.

Just one more opinion to read!!

Good luck with your decision,
George

[Ron C.]

Re: Side Exhaust on a 67

Thanks George. I've heard good things about StainlesswWorks side exhaust not being as restrictive as GM/original pipes.

[George J.]

Re: Side Exhaust on a 67

This information is too sketchy to draw conclusions. How about some details?

Lab dyno or chassis dyno? What type of correction?

Describe "dyno exhaust" in detail. Headers? Primary length and OD? Collector and tail pipe lengths and ODs? mufflers? Where in the system were they located?

Same for when the side pipes were tested - complete unambiguous detailed description of the exhaust system from the exhaust ports to the atmosphere exit?

Were there any other differences in the configuration other than the exhaust systems?

Duke

Duke,
I didn't go into detail since I have before. The dyno (lab) exhaust was large 3" pipes with large mufflers, and a scavenging fan, if I remember correctly, hooked up to the rams horn manifolds. Sidepipes were GM versions that were fairly new at the time, when they were still making them (or sourcing them). These, also, were hooked to the rams horn manifolds with scavenging tubes. No, and I mean no, other changes were made, including taking the time to adjust mixture. This is a rough set of numbers, but the only time I have heard of anyone doing any kind of comparison back to back.

George

[Duke W.]

Re: Side Exhaust on a 67

That's a reasonably valid comparison. The mufflers might have been lower restriction than OE, so maybe the loss through side pipes is less than ten percent, but even five percent is a lot for those who are interested in achieving maximum power, which I think includes most of us.

One of the problems with lab dyno tests is that they are usually done with headers and open exhaust. Then the engine is installed in the car with manfolds and mufflers, which is a substantial change in configuration, especially with high overlap cams. (Headers have little effect with low overlap cams.) Lab dyno tests are also expensive because of the set up time and often there are spark advance and fuel map issues that must be resolved. These issues are why I recommend installing fresh engines in the car and doing SOTP testing and tuning on the road. Then once you think it's optimized, run the car on a Dynojet chassis dyno, which will yield real world engine performance data.

Duke

[George J.]

Re: Side Exhaust on a 67

That's a reasonably valid comparison. The mufflers might have been lower restriction than OE, so maybe the loss through side pipes is less than ten percent, but even five percent is a lot for those who are interested in achieving maximum power, which I think includes most of us.

One of the problems with lab dyno tests is that they are usually done with headers and open exhaust.

Duke

Duke,
I had really only intended to see what the power was with the sidepipes, but on a lark, asked them to hook up the larger pipes and mufflers. When I asked about headers, the shop owner said that the rams horn manifolds didn't show much less power than headers in his experience. I am sure he was referring to street car installations, when saying this. I'd really like to see someone develop a sidepipe that would fit under the stock covers, but gives back 20-30 hp, without an increase in sound. I'd also like to hear a stock set with a crossover tube installed. But now I am very off-topic.

George

[Michael F.]

Re: Side Exhaust on a 67

back in the day on my first 67 put under car exhaust but left side pipe covers, tips and header pipes where it was visible somewhat from outside so had best of both worlds, put back when sold. also with hooker headers back in the day you had a terrible "S" type bend to connect header to side pipe and killed power, later hedman headers had sidepipe header that worked much, much better with no "S" bend.

[Ron C.]

Re: Side Exhaust on a 67

What's a set of unused/new-in-box NOS pipes and covers going for these days?

[Michael J.]

Re: Side Exhaust on a 67

What's a set of unused/new-in-box NOS pipes and covers going for these days?

Here's some, this is about typical, I have seen them as "low" as $3500:

http://www.ebay.com/itm/63-64-65-66-67-Corvette-Side-Exhaust-Pipes-NOS-Original-GM-BBC-396-425-427-3x2-/400375505230?fits=Make:Chevrolet%7CModel:Corvette%7CYear:1967&hash=item5d383d614e&item=400375505230&pt=Motors_Car_Truck_Parts_Accessories&vxp=mtr