BBK's Long & Short Tube Headers - The Long And The Short Of It

Horse Sense:
Previous tests have shown unequal-length short-tube headers are worth around 7 hp on a near-stock 5.0 engine, while equal-length short-tubes typically pick up around 11 hp. Frankly, we were amazed at how similar the power output was with the four BBK headers

While we had our 347 dyno mule up on the pump at Westech recently, we double-timed through several sets of headers for a quick revisit of the Mustang header debate. Our goal was to run both equal- and unequal-length short-tube headers to see if the hassles of the equal-length units were worth it. And then we moved to long-tube headers to see if 1 5/8- or 1 3/4-inch primary tube diameters made any difference-not a big test, but a quick look at the two major choices in Mustang headers.

BBK was kind enough to supply us with the following headers and H-pipe for our test.

The Test Engine
We tested the headers on our usual engine-dyno mule, a Coast High Performance 347 Street Fighter short-block fitted with Ford Racing Performance Parts Z304 cylinder heads, a stout Comp Cams hydraulic roller, and an Edelbrock Performer RPM II intake manifold, all controlled via an AEM Plug and Play engine-management computer (we'd been fiddling with the AEM computer, but that's another story).

The Results
Frankly, we were amazed at how similar the power output was with the four BBK headers. The expected trends were there, but not as exag-gerated as we had thought going into the test. The long-tubes made more torque than either of the short-tubes, but there was little to choose between the two long-tubes.

So, while the difference between the long-tubes was small, the expected higher torque from the smaller pri-mary pipes was evident, as was the higher power from the larger-diameter primaries.

Could it be the longer primary length of the equal-length short-tubes enhances torque, but at higher rpm the twists and turns of the tightly wound equal-length pipes is more restrictive than helpful?

The longer collector provides what looks to be a much easier merge from the primary pipes into a 3-inch collector. That gradual merge and unrestricted 3-inch collector diameter certainly look as if they pose no restriction, and may allow more scavenging effect.

Looking at it the other way, the Ford-style ball-joint flange forces a truncated collector, plus the ball-joint flange curls inward, well into the exhaust gas path. In other words, just looking at them, the ball joints appear restrictive, and our dyno data would certainly indicate that. Unfortunately, we didn't have a pile of identical headers with different collectors and flanges on them to sort all this out. The good news is we now have another dyno test idea up our sleeve.

Of course, much of this is aca-demic on the street. The ball-joint flanges are what Ford uses, and thus most aftermarket systems are designed to mate with them. The ball joint is also forgiving of misalignments and seals tightly the first time. It has no gasket to burn out, the hardware is good and large, it accepts high-tightening torque, and it doesn't occasionally loosen-all issues with traditional three-bolt flanges.

What we can say is, despite the possibilities of burned ignition wires, equal-length short-tube headers would seem worth the cost and hassle on moderate-power street machines. And if you're going for long-tube headers on a race car, then going all the way with big tubing is the power-savvy choice.

On the Dyno