No doubt. So will DDs, compared to a stock manifold. The missing link is what a few people seem to want to tapdance around: nobody's yet provided any evidence that headers are better than DDs on a slant-6 used in anything other than constant full-throttle race application. Max wedge, small block chivvy, hemi, Ford Windsor, Hot Rod magazine, Briggs and Stratton lawnmower engines, etc. are all irrelevant, because Dutra Duals aren't available for those applications.

Red herring and straw man don't make a very appetising dish.

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一期一会
Too many people who were born on third base actually believe they've hit a triple.

"Your mileage may vary" would be a good way to put this debate.

Thing is, the blanket statement that "headers are better than DDs" is not necessarily true. It depends upon the design of the header (6 into 1, 3 into 2 into 1, true duals, etc...). A real comparison would need to be done between a set of headers that similar in design to the DDs.

There are other factors that will also influence the choice of exhaust that would be most beneficial. What is the vehicle mostly used for? Is it a daily driver or a race car?

I see that you list your locale as Spotown, WA... a place I would imagine isn't warm for very long during the year. Headers by themselves will make cold weather driveability a pain in the neck without some modification to the underside of the intake manifold to supply heat to the manifold.

Bren67Cuda904 lists his locale as Orlando FL, a place that is warm pretty much all year I would imagine, in which case, cold weather driveability probably isn't an issue because it rarely gets cold enough to cause issues, and because of engine modifications, headers are a better choice for his particular application.

For yours, I recommend the DDs, due to the improved cold weather functions, amongst other things.

My .02

~THOR~

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1984 D100 Shorty Custom
Certified Auto Appraiser - RevItUp Classic Appraisals
President - Cherry City Bombers CC
Part of Tyrde-Browne Racing

[quote="THOR]
For yours, I recommend the DDs, due to the improved cold weather functions, amongst other things.

My .02

~THOR~[/quote]
Keep in mind that the True DD don't have any intake heat either.

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67Cuda,FAST EZEFI,340cu,CR=10.25,RollerCam&Rocker (XR268HR,#20-810-9)(#1622-16)(EddyRPM#60779,#7576), (MSD6AL,#6425) A904, GearVendorsOD, 8 1/4,3.55:1, ClassicAir

That is not so.

Dutra Duals (DD) keep the intake manifold heat and automatic choke provisions.

Dual Dutra Duals (DDD) do not have intake manifold heat or automatic choke provisions.

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一期一会
Too many people who were born on third base actually believe they've hit a triple.

I want to see proof that the DD offer any improvement over the stock manifold! I always hear people harp "show me proof that headers are better than DD" Well show ME proof that DD are better than the stock manifold.

I say run a manual choke or all electrical choke,and get some full length headers and enjoy the extra HP/TQ and fuel economy.

I have never had as much trouble with headers as everyone seems to claim. I have never had leaks,and my cold weather driveablility has not changed.Neither have ANY of my friends with their cars.Ranging from slant six up to big block.

Years ago (back in the 80s) I ran a Clifford 4 barrel intake and their long tube headers on my DD 65 Dart convert. In the winter here in VA I would pump the gas twice (no choke), start it up, let it warm up a minute or two and drive off with no driveability issues. Biggest issue I had with the headers was the front 3 tubes got pretty dented up being low hanging. Can't vouch for any extra performance from the headers, but the 4 barrel sure made a difference!

The stock manifold for these engines is pretty restrictive to start with. Factory head pipes were tiny (around 1 7/8") which creates massive backpressure under high load, high RPM circumstances. Installing a later 2.25" head pipe, help the engine to breathe, but you still run into backpressure issues because all 6 cylinders are dumping into a centralized location, not far from the center cylinders.

The Dutra Duals open the engine's exhaust up more than can be done with a stock manifold, and without the warpage, or cold weather driveability issues that most people have problems with when using headers. Your experience may vary depending on the circumstances, but in the majority, these are results from using headers.

Those who live in warmer climates may not have so much of an issue with the headers because they do not experience as much of a temperature fluxuation as those of us who live in colder climates.
You may not have, but there are always exceptions to the rules. I am glad that you haven't experienced any issues with yours, but there is no point in asking "What do DDs have over a stock manifold?" when the reasons are abundantly clear. It's pure mathematics. You have the potential to flow more with a larger pipe. With the DDs, not only are you running a larger pipe, you are now running 2 of them.

The point here is the differences between running headers as opposed to Dutra Duals, and the Pros and Cons of each. Unless someone has hard numbers to work with, all we can do is speculate as to which would work better. No one is saying DDs will outperform headers in competition, or vice versa, except in the case of a racing application where the headers have the edge. The DDs are favored because they last longer, fit the first time, "typically" improve driveability over headers, and have an unequaled backing by the manufacturer in the land of aftermarket SL6 exhaust systems.

GENT, you live in Carlsbad California, I can't imagine you have much of a cold weather issue considering how close to the equator you are. You live in a warmer climate, as does Bren67Cuda904, therefore, you don't really have the cold weather issues like the people in Washington, and Oregon.

V6 and V8 engines don't count because they heat the intake through the heads. This is a Slant 6 only issue.

If you have your heart set on the headers, by all means, please, buy them, just remember you may run into issues with them sooner, rather than later.

~THOR~

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1984 D100 Shorty Custom
Certified Auto Appraiser - RevItUp Classic Appraisals
President - Cherry City Bombers CC
Part of Tyrde-Browne Racing

Have not always lived in CA. I lived in Nevada 115+ in the summer and 20 deg. or less in the winter.No problems with headers. My brother lives in Northern Washington 80+ in the summer and sub zero in the winter;no problems with headers(his snow plow truck had headers on it!)

As for mathematics,its just that. I did not say the DD wont outperform the stock manifold,I said show me PROOF that it will. Just as everyone is asking for proof against headers.What I see is the same cast iron with sharp angles and stock port design,with just a center exit.

I just dont get how someone can push a product like crack when they have no actual proof that they even perform as well or better than stock.

Well, going from a 1-7/8" to the 2-1/4" single was a big bump up in performance. About a second for me in the quarter. That was a biggy.

Going to the Dual Dutra Duals on my present build has resulted in stronger performance on the G-tech I've been playing with. I was running about 17.2x or so as set up on the 2-1/4" Single. I am playing with 16.5x times at this stage. There is also a weight reduction to factor in, so the results aren't pure.
The general rule of thumb is a tenth per hundred pounds, That only gets me to 17.0x
The G-Tech is an OK tool, but it doesn't give the same numbers the track does. Probably due to suspension not keeping the device level. When I punch it, I get very noticeable rise in the front of the car.
So far, variability in the G-tech reading is a bit too wide.

Once I get to Woodburn or Medford, I'll have better numbers. Las Vegas doesn't count. Great track, horrible air. If I run in the 17's in that muck, I'll be happy.

CJ

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If you got the book they recommend two methods for measuring.

1) is the 1/4 mile run, like you are doing

2) stick it in second gear make the run only in second gear (power gear)... this is supposed to provide your best look at your torque band as the ratio vs. wind resistance is better (of course it makes for good banter when the cop asks you why your car sounds like it's about to crap a honda out the tailpipe and you're only doing 65 mph....)

Going from a stock pipe to the 2 1/4" for a stock-ish car is about 10 hp and 15 lbs of torque...it's hard to say the difference between the duals and the single 2 1/4"....shifting up to a 4 barrel, and better rear gears at the same makes the comparison very unfair...

Whatever you choose for your modifications, if you don't like it, you'll have to pay to reverse it, so take a moment to think about what you want out of your build and make sure you invest items that work well together...


-D.Idiot

With my current gearing, the stroker would hand grenade if I left it in second through the quarter. I'm turning about 4100 in third at 86 or so when the 1/4 clicks off.
With the new rubber, that should jack up about 400 rpm. We'll have to see how it behaves.
The best place to get a solid number will be at the track. My results won't be pure though, 'cause I just can't leave well enough alone.

CJ

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Actually It's somewhat warm from about april until november. During the summer it can be 90+ for a couple days straight. And even when it is cold,below 40, i let my car run for about 20-25 minutes before i go anywhere to avoid cold driveability problems.

If you have to let your car warm up for more than 30 seconds before being able to drive off then your car has a problem. Running the engine for 20-25 minutes is a great waste.

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Joshua

100 pounds is a tenth does not apply to a heavy car with a little motor. You may pick up as much as 2.5 tenths per hundred on a slow car.

When my ex and I were both driving my Duster she was 3.5 tenths or so faster than me. She weighed 175 pounds lees than I.

I changed from the stock pipe to 2.25" on the Duster and did absolutely nothing else. The car picked up "0".

The truth is that Doug's manifolds are better than a stock manifold, but not as good as headers from a performance end. I have run both in my red car with the same motor/trans/gear/weight. The car was a couple tenths quicker with headers.

Constantly telling people that DD's are better than headers when they really want headers to start with is just plain nuts, and a complete fabrication.

Look at it this way. You're hungry and you really want bacon and eggs. You walk into a restaurant that tells you they only sell eggs. Then they proceed to tell you that you don't really want bacon because bacon sucks and that you really only wants eggs. How long you gonna sit there until you leave?

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Official Cookie and Mater Tormentor.

Who said Dutra's were better than headers?

Sticking with iron for the street is the only motivation for going that route. Headers rule at the track. keeping bottom end is a bit more of a challenge with headers in some applications.

I've had very little trouble keeping headers sealed on the applications where I run them. Periodically there will be a problem, but it's actually pretty rare. Once they are bedded down, they generally stay put.
Now burning through cheap stuff, or just rusting the collectors. That's annoying. Pitch it in the metal bin and start over... Ceramic coatings and decent quality material solves a lot of that, as does bringing the engine to full operating temperature before shutting down. If your going to drive it as a grocery getter a half mile at a time, stick with iron.

2¢

CJ

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