Re: 427 FE engine, under car 'street' exhaust system?

[DanEC]

So far heat has not been a problem - about the highest temp I've seen sitting at a light is 80C. The oil doesn't get much above that either. Sitting at a light I do start to feel a lot of heat welling up from under the car and spilling over the side of the doors but that is pretty much typical. I have weatherstripping around my hood opening to mimic the street roadsters and that is probably not a good approach. I think a few pieces of intermittent weatherstripping or hood bumpers would allow that area to help vent underhood heat a little. I do have ceramic coated headers, head pipes and mufflers and a lot of insulation in the cockpit. Those mufflers are right under the seat and about 1 inch off the floor board and when I've shot them after a drive they are somewhere around 500F. I have Lizardskin on the underside of the floors and B-Quiet and Kool It on the top side under the carpets. It's mostly the heat welling up from underneath at stop lights that I notice.

[Donunder]

I saw a story in the April 2016 issue of Classic and Sports Car magazine about a firm called Taylor Automotive in East Sussex. They specialise in "difficult' engineering solutions. I don't know whether their expertise extends to headers but if not they'd probably be able to point you in the right direction. They're at www.taylor-automotive.co.uk

[Paintwerks]

I am running a supercharged 6.2 litre LSA in my alloy-chassis Australian-made Pace 427SC. I had a custom made 2.5" stainless under car system with mandrel bends fabricated to fit the car by a local race shop that does work for some Australian V8 supercar teams.

My Cobra's design is a little different in that the exhaust can be located each side inside a frame rail channel on the outside of the car (but under the body). From the side of the car, you can only see about 10mm of the exhaust as most of it is tucked up into the channel. I am going to get that part powder coated in matt black. Had I run 2.25" tubing you probably wouldn't have seen it at all...but I needed the 2.5" for flow with the blower.

The exhaust runs into 2 x high flow 2.5" mufflers concealed under the body and the tips are turn-down type which sit flush with the body and are not visible from behind the car. Clearance is tight, but it all fits.

I am also running catalytic converters in the car as well just after the 4:1 headers so the system is fully emissions legal and tested/complied as such.

[Silversmith]

You guys know you can have custom NASCAR style flat rectangle pipe sections made for crossing under frame sections where needed a 1"X 4" = 4" pipe if you need that much exhaust. Or a 1"X 3"=3". NASCAR runs them from the header to the exhaust point & the flow is the same & so is the sound That is my plan; @ least under the frame points. But as usual, life's event have my conversion postponed. But I will get there one day soon. Just find a local muffler shop/ or just about any skilled fabricator/welder can make theses sections up for you with out huge cost either!

[DanEC]

On rectangular you have to go quite a bit bigger than that I believe. The cross section of a 2-1/2 inch pipe is 4.9 sq in. So you would need a 1 x 5 to get equivalent area. But to get equal flow I think you would need to go even bigger since the boundary circumference on a 2-1/2 inch pipe is 7.85 inches and a 1 x 5 rectangular pipe would be 12 inches - creating a lot of boundary drag and restriction in the rectangular pipe. Someone who remembers their flow mechanics courses better than me would need to figure out an equivalent size. Oval piping is probably a better approach where ground clearance is needed. .

[AC Ventura]

The area of a circle is diameter x diameter, divide that by 4 and multiply by 3.142.

Therefore the area of a 3" diameter pipe is 7.069 square inches.

That I am afraid equates to a much bigger rectangular section of 1" x 7" or 2" x 3.5".

However an oval section of 2" x 3.96" also equates to 7.07 sq in and is possibly the most practical alternative.......but very difficult to bend round a chassis.

What would really be beneficial, is for example with a 500hp big block, running 2" primaries, what is hp loss between 2.5 and a 3" collector pipes, if any?

[Buzz]

Its generally not necessary to bend the oval sections around the chassis. They only need to be used under the frame - maybe with horizontal bends in a flat plane - where ground clearance is an issue. Oval to round adapters can be used to transition to header connections and tailpipe sections that need to bend over the rear suspension.