Tom Wilson
April 1, 2001

Step By Step

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MAC Products manufacturers of a large line of popularly priced short-tube headers, performed our header installation. Our installation was of these 1-5/8-inch, unequal-lengths on a five-speed ’86 GT. Known at MAC as PN I8693 and built from 16-gauge mild steel, they retail for $159.50 with this shiny “industrial plating.” For $10 more, MAC offers a high- temperature, silver-paint option in lieu of the plating.
As with most headers these days, MAC’s are supplied with studs and nuts at the header-to-H-pipe attachment point. This makes installation much easier, as one person can handle putting on the nuts. With free-floating bolts at this junction, installation is something of a pain and requires a helper. That, or you can tack-weld the bolts to the headers if you have a smoke wrench.
After disconnecting the battery to avoid arcing wrenches around the starter motor, the best place to begin is on top, where the air hoses can be removed. On our speed-density car the entire air filter assembly and air tubing was removed for maximum clearance.
With the engine intake air tubing out of the way, the Thermactor air plumbing on the passenger-side header is visible. Remove the small vacuum line atop the one vacuum canister, then remove the two larger hoses from the air valves. The idea is to free the Thermactor connections near the header so the H-pipe is free to slide rearward.
Before unbolting the headers from the heads is the time to undo the H-pipe, so get under the car and remove the header-to-H-pipe hardware. You’ll find it beneficial—perhaps necessary—to remove the oxygen sensors too.
With the H-pipe free from the remainder of the exhaust system and Thermactor air plumbing, it’s time to muscle the H-pipe to the rear of the car far enough to clear the headers. This is best done after lubing the H-pipe’s bayonet hangers—where the steel rods mate with the rubber bushings—with spray oil. It lets the two slide much more easily. While it is not technically required to completely remove the H-pipe from the car, it does ease header installation.
Going back topside, the headers can be unbolted from the cylinder heads. The passenger-side bolts are a little tight because of Thermactor air plumbing, while on the driver side, things are out in the open. Simply undo the header bolts and pull the header back, then up and out. You’ll remove an engine-lifting hook doing this on each side of the engine. Just set them aside for now. On the driver side you’ll also have to remove the dipstick and tube. This assembly unbolts from the headers at the top and simply pulls out of the oil pan at the bottom.
With the headers out, move on to the header gaskets. The old ones may come off nicely—in one piece—or they may be dirty dogs and tear. In any case, scrape off whatever is left on the cylinder heads, then put on the new gaskets. The new gaskets go on dry, with no high-temp silicone or other glue. To install the new gaskets, you can stick two bolts through the end holes in the header, hang the gaskets on these bolts, and attach the assembly to the heads, or cut the end gasket holes so they are slots, open end facing down. Then loosely install the header with the two end bolts. Drop the gaskets in place between the headers and heads, and finish up the installation. Either way works fine.
Unequal-length short-tube headers are most easily installed from the top on both sides of the engine as shown. Equal-length headers are the same, except the passenger side is sometimes easier to snake in from below, as illustrated in our lead photo.
As you install the header hardware, a few details require attention. Here is the passenger-side engine-lift bracket and its two bolt/stud combinations at left. To the right is the much smaller bolt and tab MAC supplies. If you want the engine lift, fine—bolt it to the rear head pipe, the one closest to the firewall. The rearmost bolt on this pipe also provides an attachment point for a Thermactor hose bracket. You can reuse all the stock hardware here and do fine; or you can omit the lift bracket and fit just the small tab under the rear header bolt. This provides an attachment point for the Thermactor hose bracket, using the small bolt provided by MAC.
It’s an unusual angle, looking up from under the car at the rear of the passenger-side header, but it shows the MAC Thermactor air bracket to good advantage. As would most enthu-siasts, we elected not to refit the engine-lift bracket.
On the driver side, the only special requirement is fitting the dipstick tube. With some headers, including MAC’s, a longer header bolt is supplied to go with the dipstick tube. It fits on the rear bolt of the second cylinder on the driver side. That’s the fourth bolt back when counting header bolts from the front of the engine.
Fitting the dipstick tube on the driver side can be a minor pain, as it seems to fit eight different ways—sort of. In reality, the dipstick dives between the third and fourth header tubes, and it attaches its bracket to the second tube’s rear bolt. The trick is to fit the header loosely to the engine, slide in the dipstick, and only then finish off the header installation by tightening the header bolts. That the new header tubes are larger diameter than the stockers doesn’t help. In fact, it is often necessary to grind off some of the dipstick tube’s bracket so it will fit between the header bolt and the header tube. This is especially true with 1-5/8-inch headers.
About all that’s left now is hooking up the H-pipe. Start by lubing the rubber bushings the H-pipe hangs on. Fighting the H-pipe back into position is physical enough without working against dry mounts.
There’s no good trick to lining everything up on the H-pipe when installing it, although working with a hoist really helps. Set the H-pipe loosely in position, snug the hardware up a bit at both the headers and mufflers, then check the tailpipes. Make sure the tips haven’t rotated. They could look lopsided and can lead to the tailpipes knocking against the floorpan. Only after you’re satisfied everything is in alignment should you fully tighten the hardware. Hook up the oxygen sensors, reconnect the Thermactor air plumbing by the passenger-side header, and refit the intake air plumbing.

For many 5.0 enthusiasts, installing a set of short-tube headers is the most labor-intensive task they'll perform. Unlike underdrive pulleys or an air meter, headers vary widely in their shape and fit. Add in the corrosive effects of heat cycling, the harsh underhood and undercar environments, and header installation can also mean tangling with crusty, obstinate hardware. The first-time 5.0 header installer can encounter a few unexpected pieces of hardware as well, and when finished, he may realize he's faced with an unsettling amount of "extra," unused studs, nuts, and brackets--not reassuring.

All that said, aftermarket headers are proven 5.0 power-builders. With a minimum of instruction and tools, the job is well within the grasp of the home mechanic.


Exotic or precision tools are not required for short-tube header installation, but you'll definitely want a reasonably full set of screwdrivers, wrenches, sockets, and extensions. A universal swivel for your socket set is also nearly mandatory. A can of spray oil such as WD-40 should also be on hand, and you'll want access to a hoist, or tall jackstands at the least. There is no huge under-car clearance requirement for headers as there is for--say--transmission or clutch work, but comfortable working room under the vehicle does help. Eye protection from falling crud and metal chips while under the car is also mandatory.

Engine Mounts

Sagging or collapsed engine mounts are a real issue with the aging 5.0 fleet. If your 5.0 has 100,000 miles on it, it's time for new mounts. Inspect the engine-driven radiator fan. Does it rub on the bottom of the fan shroud? This is a sure sign of sagging mounts. If so, header installation will be more difficult as the starter-to-K-member clearance is reduced. With unequal-length, short-tube headers, this can be troublesome. With equal-length headers, collapsed engine mounts can make header installation impossible.

A few bucks spent on replacing the engine mounts will make a world of difference in the header installation. Also, if you have a crusty oil leaker on your hands, then a few minutes with a pressure washer will make life much more pleasant as well. Finally, while header installation doesn't mandate spark plug removal, it is a great time to install a new set of plugs because they are so easy to reach.

Making the Swap

Topside, the driver-side header is complicated only by the dipstick. On the passenger side there is a bit of Thermactor air plumbing to unclamp--none of which is anything major. You'll also find an engine-lift bracket on either side, which simply comes off with the header hardware. If you find the passenger side somehow a little tighter, it's not your imagination--5.0 engines are slightly offset to the passenger side of the engine compartment for steering clearance. Removing the old headers requires sliding the H-pipe rearward under the car. So, you'll need to remove the H-pipe hardware front and rear, then slide the assembly rearward on its bayonet-style mounts.

Inserting the new headers is typically done from the top, although some equal-length headers are more easily installed from the bottom. It's up to you whether or not to reinstall the engine-lift brackets. They're handy when removing the engine, but they're also a bit of underhood clutter you may want to do away with. Under the car, lining up the H-pipe can take some muscle, which is where some spray-on oil applied to the rubber mounting bushings helps tremendously.

Typically one mechanic installs headers, although some headers may demand a helper. These are the headers using bolts and nuts instead of studs at the header-to-H-pipe connection. When using bolts, it will take one guy holding the bolts from the top and a helper underneath to run on the nuts. Otherwise, short-tubes are a one-man job.

Once the headers are on, run the engine to check for leaks--it's doubtful you'll have any thanks to Ford's ball-type joints--then drive the car a day or so to heat cycle the installation. Let it cool, then put a wrench on all the hardware to make sure it's tight. You'll likely find the occasional loose bolt. After that final tightening, however, the header hardware should stay tight indefinitely.

Horse Sense: Worth around 7 hp on a stock or near-stock engine, short-tube headers are a great compromise between engine efficiency, emissions requirements, and ease of installation. Admittedly still a bit crusty to work with, fitting short-tube headers is a breeze compared to the long-tube variety. In the bad old days, it could take an entire weekend to fit long-tubes to a big-block and then they’d never seal. Today’s stuff is a breeze by comparison.