Headers Without Intake Manifold. Worth It?

First off your photo shows headers for a V8 so the pairing you describe would be based on the firing order not the position on the bank of cylinders If that is a SBC set of headers which it looks like to me the pairings would be 1 and 3 5 and 7 on one bank and 2 and 4 6 and 8 on the other bank. SO nothing like a 4cyl with a 1-3-4-2

Your comment is wrong a Tri Y design when dealing with an engine that has a 1-3-4-2 firing order pairs the 1 and 4 then 2 and 3 I spent months working on various designs for these headers before slogging through roughly 3 weeks of actually figuring out how to cut and fit all the different pieces together to end up with all the tubes the same length I ended up with #3 being .69" shorter then the other 3 and had to live with it. I assure you I designed and built the headers as close to the theoretical ideal as possible. I worked through 3 different header design programs before deciding on Primary tube length verse secondary tube length and tube ID. Granted there were compromises, But as the professional race car header builders I was in decisions with while designing and building them told me there are always compromises somewhere.

Sorry if I seam a little defensive I nearly killed myself building there headers I am not a Welder and theres like 50 tubing welds that all had to be ground down smooth and that nearly killed my back standing bent over for 3 weeks grinding welds on my belt grinder flap sander and with the angle grinder. I put a lot of effort into these.

 

The picture I posted wasn't application specific. It was posted to illustrate the tri Y design itself. 2 cylinders creating a "Y". 2 "Y"s connecting to become a 3rd "Y".

As I noted in my edit, I missed the third collector in the last picture, and corrected my statement.

 

I've run headers on a bunch of stuff and nary once did the mileage not go up with just normal driving. Yes, if ideal, they would be tuned for a certain optimum rpm but most of them have some benefit over a pretty wide rpm band. And whether they crack and leak depends on who built them. Another case of you get what you pay for.

 

Don't forget, header installations include freer flowing exhausts as well. I'll wager any increase in economy is less about the headers and more about the rest of the system breathing better.
Personally, I too have run headers on a number of different vehicles over the years and other than a nicer exhaust note, have not seen any increase in economy. In fact the economy usually goes down since the header set is normally included with the 4BBL manifold, carb and (usually) a cam. The temptation to exercise the upgrades usually costed me any economical increases.

 

A real world example

1967 T code Mustang 6cyl 200L6 3speed 3.20 gears (sorry forget the tire size) In 1967 Road and track in their road test got 19.5mpg .5 mpg better then the 289 V8 version

I changed the car with these changes

Holley Weber 5200 progressive 2bbl on a home made adapter supplied by a fresh air intake with the pickup right up under the lip of the hood in front of the core support using a K&N style small cone filter.
MSD-6A Spark Box, Petronix Ignitor I magnetic trigger in a 1968 adjustable vacuum advance distributor Accel suppresion wires.
Clifford Research 6 into 1 header with the addition of a 3/4 exhaust port splitter into a 2.25" Mandrel bent exhaust through a Cheap Turbo muffler
Electric Fuel Pump
Electric Thermo controlled fan
Swapped to a 1977 RUG 4spd with an 18% OD
light weight Aluminum wheels

The car then got 26mpg commuting on county roads 85 miles a day round trip for the wife going to work she commonly drove 70mph She drove the car to work for about 110,000 miles after these improvements her aggregate mpg ended up being just under 24.5mpg.

On three separate trips in California on the long flat sections of I5 North of Bakerfield we got 30 and 31mph for at least two tanks in a row.

On a trip to Reno passing through Grass Valley in NE CA I ran the car at over 100mph for 45 minutes getting it as fast as 110 a couple times. I still had a little throttle left. This was with the car loaded for a long weekend trip and two heavy people.

An automobile engine is nothing but a big air pump the more air that can pass through it the more power it can make if the load remains the same the efficiency will increase. SO improving the exhaust allows the air to exit the engine easier which make it more efficient and it will increase the mileage. Your driving style might not show you those improvements but they are there.

YMMV

 

Hmm, it's not automatic that freeing the exhaust gets you better mileage. If it is the case that the exhaust system does a better job of scavenging gasses out of the cylinder then it improves the volumetric efficiency of the engine. Doing that means you get more fresh air/fuel mixture into the cylinder, so you will actually use more fuel per firing of each cylinder. So, if you can use that power to say hold a gear longer or get into a torque peak then you might get better economy despite the increase in fuel used but it's not a guarantee. I'm not suggesting some people don't get better mileage from a free-flowing exhaust, I'm just saying the air-pump explanation is simplistic and there are lots of factors at work to give automotive designers fits.

 

So if you buy a die grinder new gaskets and tear down the engine so you can port match everything...you can feel good about...getting...uhh...I think I'll just put in that small block???

Dale

 

Ive had headers on some things that worked well. Others that cracked and rotted out in no time. Anymore I just run iron manifolds on everything along with a large single exhaust. My 225 has iron manifolds, single 2.5 inch exhaust and a Dynomax muffler. Runs pretty good and no leaks.

 

I went a different way I made the Headers port match the Block on the 134L so it was quite easy since the ports are basically 1.375" round holes. I maybe could have gained a tiny bit of flow had I opened up the ports a little but the 134L in stock configuration will flow well enough to turn over 5000 rpm (I've done it unless you can figure out how I drove CHUG over 80MPH clocked by a BRAND NEW 1976 Honda 750/4 right beside me) By the way no damage what so ever to the engine after that I drove it another 3 months to work and all over hell and gone the summer before I left for college including a 4 day 800+ mile trip to the Alvord Desert and back.

SO knowing the engine can flow well enough to turn well past what I will do with it now as a 63 year old guy I figured no need. The ports were plenty big.

To the Fast Tractor crowd reading this its ok if your sure your jeep can't go over 43mph without blowing up. Some of us have looked beyond the barn yard and its wondrous.

 

I've got an F134 that used to live at 6800-7000 rpm for 10-15 minutes at a time! I parted another that had the wrist pin pull out the bottom of he piston, but that was after 4 seasons of racing. The headers on those are 4 individual 1 7/8" pipes straight up 3 1/2 feet to a 4" collector.
-Donny