I have super six sl6 and the exhaust pipe is from header to tail 1 3/4" and this is only construction that I can buy from shop here. I would like to know what I get if I make myself bigger exhaust ( mileage, power). And what is best size for pipe 2 1/4", 2 1/2" or bigger? Do I build all the way with same size pipe?

I also would like to know, what is the outlet diameter of header, I would not like to open that flange only for metering it, if someone can tell me it.

If there is somenthing else I should notice, please tell me.

Joug

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Sorry, my english is not very good

Joug, it depends on what you want to do and how much money you want to send...
My header has a collector of 3". But I put a Thrush muffler to connect to header but the other end is 2 1/2". So I will be putting on 2 1/2" pipe to finish the exhaust. There will be little pressure with that size pipe.

Joug,

Using the stock exhaust manifold, the biggest pipe you can use effectively is a single 2.25", and that will require a little grinding on the exit port of the manifold to make that effective. Without any grinding, a 2" exhaust is the biggest that will help you. You will probably notice a small power and mileage increase, but it will not be too much.

Putting a header or "Dutra Duals" on will give more noticeable mileage and power improvements - maybe 5-15 HP and 1-3 MPG.

With bigger exhaust, the carb will tend to run leaner if you leave it alone. You may want to jet up (richen), but this will not hurt mileage if done correctly.

Lou

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Home of Slant6-powered fun machines since 1988

Thanks

So mayby i'll leave it like it is. Grinding without disconnecting manifold might be too difficult. And i would like to do somenthing else for the engine same time when and if i'll take apart manifold. That time dutra duals would be very good solution, and probably only ones here in finland. Problem is that shipping is quite expensive and maybe there is duty also. But all that time i've been at this site and first time heard of them, I've been very interestered of them.

One thing about Dutra's what i've been thinking, when modificating other side manifold, should it be supersix manifold or are all slant manifols ok?

Joug

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Sorry, my english is not very good

Hey Joug,
2 1/4" pipe is a good size for the slant six. i would recommend 2 1/4" from the manifold to the muffler, then 2 1/2" over the axle...if the over axle pipe is crimped then you'd want to step up to 3". remember, every bend, no matter how smooth, creates restriction. this is probably more important for racers because they are trying to squeeze out every possible bit of power. good luck with your exhaust!

-Don

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Forget the flowmasters...here come the good ol' GLASSPACKS!!!