How to select the right header...

This is a FOX chassis "car", or at least what's left of it. We cut up a "perfect car", cut out everything that was in the way, and removed everything from behind the firewall, to make it easy to roll around the shop while designing headers for that style vehicle (1979-1995 Mustang). All headers are designed with the OEM height engine mounts and OEM K-Member in place. If it fits in this car, it will fit in your car, UNLESS, you have made too many changes to the chassis from the firewall forward. We used the same process when designing the headers for the '65 through '73 Mustangs, too.

RCI CUSTOM HEADERS - (909) 552-3690 - geoklass@yahoo.com

The original header (Header #1) for that specific application is fabricated inside the cut-away car. Header #1 is NEVER sold, it is used to make the steel fixture shown above. It's kept as a reference so that as new headers are built in that fixture, we can compare where all the tubing cuts are, to insure that the customer gets a header that will FIT, assuming of course that his FOX chassis vehicle is as "OEM" as the one in this photo. Aftermarket K-Members and aftermarket Motor mounts may LOOK like they are the same as OEM, but some are and some aren't. You can see in this photo how this header (2" primary) has some tubes on the inside and some on the outside of the steering shaft, in order to both fit and also to insure a nice radius. This is what we mean when we tell people that if your engine mounts lower the engine, you may have interference with either the chassis or the steering shaft.

RCI CUSTOM HEADERS - (909) 552-3690 - geoklass@yahoo.com

As I said on our website "If it was easy, anyone could do it". www.georgeklass.net

RCI CUSTOM HEADERS - (909) 552-3690 - geoklass@yahoo.com

General karthief said:

The December issue of Car Craft has a short vrs long tube header dyno comparison, the long tube was 1 3/4" and the shortys were 1 5 /8" , they also tested a set of factory shorty headers and stated there was no difference between the factory and the aftermarket shorty headers, the test mule was a 351w crate motor with 385hp claim.
I bring this up because of what you say about the collector design, obviously the short tube headers have a 'ball socket' type merge point (they added about two foot of pipe to the header) and the long tubes have a collector and three bolt flange with about a 18" extension . I would think the results a slightly bias toward the long tubes.
#1 header tube size (I state this because of the advertised hp of the test mule)
#2 merge point differences (ball socket vrs traditional collector)
#3 the length and size of the extension after the header
I realize the difference in hp and tq are, in reality, small but it starts a conversation.

Click to expand...

Not knowing anything about the engine, or the cylinder heads, or the RPM range, etc, etc, it's kind of tough for me to make any relevant assessment here, but I tell people all the time, don't laugh about 1 5/8" headers, long tube or not. If 1 5/8" headers are the right size for a particular engine, bigger headers are not going to improve it. I tell people all the time, think about the restriction in the exhaust system, and where it is. In my opinion, it's in the exhaust valve area. 95% of all the exhaust valves in aftermarket Ford cylinder heads are only 1.60" in diameter. A 1 5/8" header measures 1.62", so we could say that they are the same, however, the exhaust does not go through a 1.60" hole in the exhaust port because the inside of the valve seat is probably only about 1 1/2" in diameter. THAT is where the restriction is, particularly on a street type car. Engine builders, I have found, typically seem to spec out header diameters that are too big for their street/strip customers. Unless your engine is pumping out 450 to 500 horsepower, my opinion is that you are better off with a 1 3/4" header than anything larger, for a street/strip engine. You can't make up in headers what your cylinder head exhaust port won't let you do. It's like an hourglass. Everyone can visualize an hourglass, a tube on the top, a tube on the bottom, and a restriction in the middle. Doubling the diameter of the tube on the bottom will NOT get the sand past the restriction any faster. The restriction is the restriction and its not going to go away by making the tube underneath it bigger.

96pushrod said:

Man I had this problem with a set of headers. I had it clearance the flanges where I needed to get a spark plug socket in. Was a pain in the ass.

Click to expand...

I don't think that many people (or many header companies) realize that different brand cylinder heads have different spark plug angles, and the flanges have to be designed accordingly. This is the difference between a "one size fits all" header and one built for your specific combination. Here's another potential problem area, "head studs". Head bolts don't stick up very much and don't cause issues with the flanges, but some heads using head studs do protrude higher than the head bolts would, and won't let the flanges drop down far enough to line up with the ports or the flange bolt holes in the heads. Provided that the customer mentions that he has head studs when ordering headers, we can modify the flanges to clear the head studs. I have also seen some header company flanges that stick up too high, and can keep the valve covers from clamping down on the valve cover gaskets, causing oil leaks.

RCI HEADERS - (909) 552-3690 - geoklass@yahoo.com

This is a 409 Chevy engine mounted in a 1960 series Chevy II, designed as an all out race car in the A/FX class.


This is what the header looks like without the front end of the car wrapped around it. At the time, NHRA permitted open headers in the class but still required that the stock exhaust system was intact (exhaust pipes, mufflers, etc.). This is NOT a long tube header, this is what we call a "Mid Length" header today.


RCI is one of the few (maybe the only) header company that offers a competition style "Mid Length Header" for 1964-1973 and 1979-1995 Mustangs, with primaries of 1 3/4", 1 7/8" or 2". Do your headers interfere with transmission removal or changing clutches? These "Mid Length Headers" will eliminate that problem...

RCI Custom Headers
(909) 552-3690
geoklass@yahoo.com

General karthief said:

Do they work well with full exhaust

Click to expand...

Yes they do. In fact, on the dyno with a full exhaust, the difference between a Long Tube header and a Mid Length header is almost un-measureable.

It wasn't just Super Stocker and F/X cars that used "Mid Length" headers. Some of you older guys will remember that the term "Long Tube" header was not used as a description for headers. Headers were just called "Headers" and the length of the primary tubes was not much of a consideration. A well designed header had nice radiuses and got the exhaust out and the collector had some scavenging characteristics. Some racers preferred the 4 into 2 into 1 design (Tri-Y design) and some liked other designs and for the most part there was no consensus. Headers, like many other high performance components were always a compromise, both in primary diameter, primary length, and even collector size. The "perfect" sizes does not exist, since an engine does not run at only one RPM, it runs through a bunch of RPM's, from bottom end, mid range, and top end. And when you install a full exhaust system on the car, the header design is even more of a compromise. There is nothing wrong with a long tube header, if anything, it seems to favor the bottom end more than the top end, but every performance component on your car favors one end of the spectrum more than the other end. A bigger carburetor favors the top end more than the bottom end, as does a radical camshaft, but we have to remember, a car is NOT a dyno, it has to make good power all along the RPM curve, not just at one end or the other, and that is the compromise.

The Tucker & Stoll AA/SR above (Supercharged Oldsmobile engine) is an interesting example, since it was basically unbeatable in NHRA competition in the Street Roadster Class. These headers are an early example of a Mid Length header. This was no light weight car, it weighed more than most FOX chassis Mustangs, around 3400 Lbs. It had an all steel body (a 1928 Chevy roadster body) and a stock frame, and because of the crappy drag slicks back then, a lot of ballast in the back. The Olds engine was no lightweight, lots of cast iron in the block and heads. One of the bigger advantages in this car was that it was one of the first to use the B&M "stick-hydro" transmission, an indestructible 4-speed automatic trans. The engine made good all around power, we took it out of Dave Stoll's ski-boat (that ended our water ski season at Lake Tahoe that year).

How does a boat motor work in a car? Just fine, the engine does not know the difference, it makes good power or it doesn't. In a ski boat, there is no such thing as the need for bottom end, if you jump on it from a standing start, it just spins (cavitates) the prop (kind of like blowing off the tires in your car). If you jump on it when it's just cruising along at 40 MPH, you had better be hanging on for dear life. Tug boats have big props, ski boats do not. By the way, there is no such thing as "long tube headers" in a ski boat, there is no room for them.

When I talk to guys on the phone about headers, of course we will give them the headers that they ask for, but I always question them about what they do with their car, whether it's an all out race car or a total street car or a street/strip car. Everybody's needs (or wants) are different and sometimes I wind up talking them out of what they say they want and selling them something that will work just as well (or better) for less money. A lot of guys want Long Tube headers, not because they are the right combination for their car, but because "everybody has them, so they must be the best choice". Many times the Long Tubes are the best choice, and many times the Mid Length headers are a better choice, if for no other reason than they cost less than the Long Tubes, and the horsepower difference is so minimal. This is why I love my job...

George Klass
RCI Headers
(909) 552-3690
geoklass@yahoo.com
www.georgeklass.net

(I'm frequently not near the phone, please send me an email note with your phone number and I will call you back.)

Advantages and disadvantages of Long Tube Headers:

I guess it can be said that Long Tube headers are the defacto standard when it comes to high performance exhaust systems. The primary advantage is that the length of the primary tubes is more in line with the general power of the torque (or power) curve of the engine. Think of a one cylinder engine, which for the sake of simplicity has only one intake and one exhaust port. On the exhaust side, it has one exhaust primary tube. In theory, the length of that tube should correspond with the RPM where the maximum power will be. If the engine is set up to produce the power at or close to the bottom end of the RPM range (let's say 1500 RPM), the length of the tube should be a certain length. If the engine is set up to have the maximum power in the mid range of the RPM curve (let's say 3000 RPM), the length of the tube will be a little shorter. And if the power level is designed to be achieved at the top end of the RPM curve (let's say 6500 RPM), the length of the tube should be even shorter.

Of course, we are talking about theory here, not reality. Very few engines run at only one RPM.

Now, let's take our one cylinder engine and add seven more cylinders (a V-8). Let's say that based on the power level of our engine (and other factors), we determine that the primary tubes should be 30-inches in length. Based on that, we should have headers with eight "equal length" 30-inch long primary tubes. But here is where things get tricky because if we are building headers for a normal automobile, the headers have to fit into a fairly cramped area, and clear the steering, the chassis, the starter, and a bunch of other stuff, and still fit into a common collector. Plus, the cylinder head is about two feet in length, front to rear, which means that the front exhaust port is about two feet further forward than the rear exhaust port on that head. How in heck can you get all the primary tubes to be equal length in that scenario? Well, it's almost impossible. You can lengthen the rear primaries by putting some bends in them, in effect having them aim forward before them curve to the rear to give them more length but it's still almost impossible to have them come out to be dead nuts equal. The good news is that it is not that big a deal. It just means that each of the eight cylinders has a "slightly" different length which might mean that each cylinder has a slightly different RPM power curve. Again, no big deal because we are not running at only one RPM power curve (which is why they call it a curve), we are running at a power "band", which means that we want power from maybe 2000 RPM up to 7000 RPM. Like everything else in life, the length of the primary tubes in a exhaust header are a "compromise", just like the length of the intake runners are in the intake manifold.

RCI Long Tube headers have a typical primary tube length between 28-inches and 33-inches.

I mentioned "other factors" when determining where the RPM power band should be. One factor is the weight of the car, another is how the car is to be used (street only, street & strip, strip only), another is number of speeds in the transmission, and also the rear end ratio. 30-inch primaries are about right for a 3000 car with a 3 to 5-speed transmission, a 3:73 rear end and about 400 HP, that can run well on the street (which means it has a full exhaust system) and at the track.

What are the disadvantages of Long Tube headers?

They usually cost more, they are usually more difficult to install, they weigh more, and they can get in the way of some transmissions (not an issue with RCI Long Tubes, ours are custom designed to fit around any and all transmissions or bell housings), and there is a possibility that your ground clearance may be reduced.

I will follow up with similar discussions about RCI Mid Length headers and RCI Front Exit headers over the next few days

George Klass - RCI Headers
(909) 552-3690
geoklass@yahoo.com
www.georgeklass.net