7x= is 2 inch exhaust system too small?

[Deleted User]

I just had a new 2" exhaust system installed on my 7X coupe. I've been told that I probably should have gone bigger, like 2 1/4" or 2 1/2". In your opinions, is 2" exhaust pipe too small?

Unknown

Do you have headers (or split exhaust manifold) and duals?

Ol racer

I think 2" is a little restrictive for a modified motor if you do not have duals. However if not driving at full speed it may be adequate..

[Deleted User]

Dave53-7C wrote:

Do you have headers (or split exhaust manifold) and duals?

I have the split exhaust manifold... and single exhaust.

Unknown

Well, there's your problem. The idea behind the split exhaust manifold was to allow the use of a dual exhaust. A single exhaust defeats the purpose of having a 7X dual exhaust adaptor.

[Deleted User]

The split exhaust manifold connects to a single factory header and collector (not two seperate headers like Clifford). This is why I stayed with the single exhaust.



The header pipe exit is 2" so this is why the shop had recommended the same size pipe. The car runs fine with the 2" but a buddy of mine thought I should have gone bigger. It has a magna-

-flow muffler which is supposed to very good.

Unknown

Seems like you have only part of a true 7X exhaust manifold. If the intention was to have a single exhaust, there would have been no need for a special 7X manifold. I liken this to having dual exhausts, but merging them into a single pipe.

[Deleted User]

This manifold was designed for the race car.



Look at the pic it was two pipes down to one that were joined to a short resonator to provide proper backflow I think. Then two pipes exit the resonator out under passenger door.

[Deleted User]

Dave53-7C wrote:

Seems like you have only part of a true 7X exhaust manifold. If the intention was to have a single exhaust, there would have been no need for a special 7X manifold. I liken this to having dual exhausts, but merging them into a single pipe.

As far as I'm aware (and I might be wrong) but there were only two parts of the 7X exhaust system, the factory split manifold and the factory header pipe that connects to it. I do have both. If you click on this link below you will see the second picture is my engine on the engine stand. Not too clear a pic of the exhaust but you can see a view of it.



http://www.classiccar.com/forums/showthread.php?t=15481&highlight=hudson+race+engine&page=5

Unknown

Sean's pic is accurate. Think of the original system as a header, but instead of having a pipe for each cylinder, three cylinders shared a pipe and terminated into a collector. I guess that's why installing true headers on a Hudson isn't really that far off stock...stock car that is.



To cut to the chase and answer the initial question directly, Flowmaster suggests a 2 inch pipe diameter for each 100 hp or 100 to 150 cu.in of engine displacement. Using that formula, it would appear that your single 2 inch pipe is have half of what is called for.



I guess the bottom line is that if you are happy with the performance, keep the 2 inch pipe.

[Deleted User]

51hornetA wrote:

This manifold was designed for the race car.



Look at the pic it was two pipes down to one that were joined to a short resonator to provide proper backflow I think. Then two pipes exit the resonator out under passenger door.

Yup, this is the unit that is on my car(with the split manifold).

464Saloon

I have got 2.5 running through a Dynomax, behind Clifford Headers. The collectors on the Cliffords are two inch but we couldn't get two two inch pipes between the firewall and frame so we ran two 1 7/8 pipes into the 2 .5 which was as big as I could getr through the frame hole. With a little modifying I can upgrade to a 3 inch which is my goal at this time. I think a 7x should have at least a 2.5