Does anyone have an experience directly comparing long tube headers (3-2-1) and Dutra Duals (call them shorty headers?). With the firing order of the slant does the individual tubes for the 3-2 add any value? This is assuming the 2-1 is the same distance from the head in both cases.

thanks,
Jim

In a dyno test conducted a few years ago, the Dutra Duals added 11 HP over a factory cast iron exhaust manifold up to and around 4200 RPM. Headers of any type are likely going to have more gain than that. Long tube, especially if they are equal length or as close to that as possible will be the best choice if your goal is maximum gain. There are pros and cons to headers as most will tell you, but for cost versus HP gains, headers will win on that front every time....

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There's no such thing as too much cam....only not enough engine!

Jim
It is a deep subject and so dependent of what you want to accomplish.
Short manifolds don't add much torque.
Long header pipes have a sweet spot and above and below that RPM are less effective.
Here is a picture of Pete McNicholl's dragster.
Using a Hyper Pak intake and long tube headers he went real fast a long time ago.
Pete was a Ramcharger, they applied ram tuning to engines.

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Hyper_pak

I agree on a V8 I am just not as convinced on an inline 6... I am just can't convince myself there is enough interaction between cylinders 1,2,3 and 4,5,6 to matter.

Jim

It depends on your objectives ie... bang for the buck. Headers will always dominate over manifold type exhaust for numerous reasons. Shorty style tube headers have some benefits, mostly fitment over a wide variety of chassis and body styles, but don't always yield the most HP compared to better, more specialized headers kits that have longer tubes and optimized collector lengths for higher output engines and high performance builds. Specialty and custom headers take it up a few notches and are tailored to produce the best HP for a specific engine build, where primary tube lengths are calculated and sometimes even change diameters several times before they reach the collectors. There are also a variety of collector designs and sizes that can also come into play to finish off the custom header. Can a Slant benefit from a custom header....? There may be a few instances in a racing scenario that one could benefit from a custom header, such as a maximum effort race engine for Bonneville, or an NHRA class racer for Stock Eliminator or Super Stock. Beyond that, a quality set of headers from any of the companies that are out there will provide you with as much gain as you could expect to get from headers regardless of what your build is, from mild to wild, N/A, forced induction, nitrous and beyond....!

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There's no such thing as too much cam....only not enough engine!

Back when I ran stock eliminator, I started with the OEM stock manifold. Then went to a "off the shelf" Clifford long tube header 1 5/8 diameter primary tubes. Car picked up. Then Jack made me an identical header but 1 3/4 tubes. The car slowed down. 65 Valiant 170/904

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Charrlie_S
65 Valiant 100 2dr post 170 turbo
66 Valiant Signet 170 nitrous
64 Valiant Signet
64 Valiant 4dr 170
64 Valiant 4dr 225

A step design header could have bridged the gap between the 1-5/8" and the 1-3/4" to have given you the same increase as going from the stock exhaust manifold to the 1-5/8" headers you used.

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There's no such thing as too much cam....only not enough engine!

I don't know when step headers started being used, but back then I had not heard of them. About 1974 or so.

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Charrlie_S
65 Valiant 100 2dr post 170 turbo
66 Valiant Signet 170 nitrous
64 Valiant Signet
64 Valiant 4dr 170
64 Valiant 4dr 225

Probably began to be popular with custom header guys like Jack Davis and others in the mid to late 70's. That's about when we became acquainted with him with our 6 cylinder. He was a former engineer with Hooker Headers prior to that and went out on his own making custom headers. His stuff was on many Stock Eliminator, Super Stock, most all Comp Eliminator classes, Pro Stock and a few Funny Cars and Top Fuel. Very expensive for the time, but they performed better than any out of the box header you could buy back then. But it showed how much more could be gained with a "step" header.

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There's no such thing as too much cam....only not enough engine!

Talked to Mark at AussieSpeed. What he has seen/believes (from conversations with Doug too) is the long tube headers may have a slight advantage at high RPM. Other than that they are similar.

Jim

That is precisely what I would have predicted based on my Performance Trends models. The volume of the cylinder is actually exactly the same as the 318 and the models said the perfect diameter for this engine no more than than 1.5" to ensure maximum scavenging and not be a restriction at high RPM...

The problem is the software does not have a way to model the 3:2:1 exhaust.

Jim

That would have been an easy prediction even without software. A relatively "stock 170" should expect to have a decrease in performance going to that large of a primary tube. That's too large of a tube even for some pretty stout small blocks.

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There's no such thing as too much cam....only not enough engine!

A few years back I ran a set of Hyperpack manifolds into a Flowmaster Y pipe and a short single outlet. Then ran the exact same setup with long tube Clifford headers. The difference between the two was withing a tenth or 2 in the quarter. This was a mildish engine that ran 14.8's in the quarter. On a full tilt race engine the headers would definitely outperform the cat iron manifold.

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2 Mopars come with Spark plug tubes. One is a world class, racing machine. The other is a 426 CI. boat anchor!

12.70 @ 104.6

I'm sure the gains would have been greater with a more radical engine build. But 2 tenths of a gain over manifolds in the quarter in your mildish build is a solid 30 HP improvement over manifolds anyway you look at it. The long tubes would definitely be an improvement for the money compared to how much the Aussiespeed/Dutra ones cost nowadays...

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There's no such thing as too much cam....only not enough engine!

When you take into account the differences in weather, altitude...etc, I figured 1-2 tenths is within the margin of error in my case. My car can change a tenth or two on the same day at the same track.

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2 Mopars come with Spark plug tubes. One is a world class, racing machine. The other is a 426 CI. boat anchor!

12.70 @ 104.6