Header Replacement

Borla on a box - last time they'll look so pretty!

Borla Headers

This project came about a little unexpectedly, while trying [in vain] to get the Carter BBD to run right, I discovered I had a rather large crack in the exhaust manifold. Fearing adverse impacts on the cylinder head if I didn’t promptly resolve this, I set out looking for a replacement manifold. For laughs, I called the local Jeep dealer parts department and inquired on the cost of a new exhaust manifold. I was quoted a $305 price! What were my options?

View of large crack on the exhaust manifold...

For starters, there are after-market manifolds out there. Four Wheel Drive Hardware has a seemingly identical-to-stock manifold for about $150 (plus shipping). But you’ll also have to add the cost of new manifold gaskets and the seals to the exhaust pipe (which may also have to be partially or completely replaced depending upon how "baked-on" is the mounting hardware). This could easily push the total cost up closer to $200 mark. Either way, stock or after-market manifolds would still be a cast-iron part, subject to rusting and cracking once again.

The other option would be headers. Headers, in concept, allow the exhaust gases to flow from the engine with fewer restrictions. By restrictions we are referring to the tight bends and smaller orifices in the overall exhaust system. Typically, headers come under the high performance category for engine upgrades. There are a few brands out there that make headers for the AMC 258 motor, one of which is Borla. But what’s really attracted me to the header option is the fact that the Borla Headers are made from stainless steel and will stand up to lots of climatic abuse. And the Borla Headers come with a great "Million Mile" warranty.

The Borla stainless steel headers cost more ($370) than the cast-iron manifolds, but really how much more? The Borla kit comes with an exhaust gasket (you’ll need to replace the intake gasket when you install the headers, so you’ll have to get one of those too), and new stainless steel hardware. Plus, the headers extend all the way back to the catalytic converter, replacing the entire exhaust system with stainless steel from the block to the cat!

Installation of the headers is rather straightforward – meaning there were very few "modifications" that had to be made along the way. The fun was in just getting to all the parts you had to remove! Essentially, to access the exhaust manifold, you have to:

Carter BBD - enemy of all late model CJs...

1.  Pull the air cleaner and rest it on the other side of the valve cover.

Intake without carburetor

2.  Pull the carburetor assembly off the top of the intake manifold.   (Be sure to take lots of notes on how everything connects – electric, vacuum, and the linkages. Lots of parts here.)
3.  Loosen the alternator mount and remove the fan belt (mine only has the serpentine belt).
4.  Remove the power steering pump and its mounting bracket. Take a few more notes on where and how each of the bolts fit, there are some slightly different length bolts but with the same thread size!

Rat's nest of vacuum line...

5.  By this point, the manifolds are mostly exposed. A small tube that feeds exhaust gases up from the exhaust manifold into the base of the intake manifold for the EGR valve, connects the two manifolds. This tube can be very difficult to remove from the exhaust manifold – so try unthreading the retaining nut from the intake side first. Having the two manifolds mounted to the engine makes this a little easier to gain leverage... but tough on access. If it cannot be removed at this point, you can remove it later. But one side needs to be removed.
6.  Remove the two bolts at the seal (where the exhaust manifold mates to the single exhaust pipe). This separates the manifold from the rest of the exhaust cicuit.

View of the block without the manifolds

7.  Remove the 12 bolts holding the two manifolds to the block. (A 9/16th-swivel socket makes this easier than a 9/16th socket attached to a separate universal swivel.)

View of hot air tube stuck (baked on) to exhaust manifold.

8.  Remove the exhaust manifold. With it out of the engine compartment, it is much easier to remove that air tube mentioned in step 5 above.  I had to use a vice!  It wasn't so much that the part was welded to the manifold, it was that the nut (attached to the hot air tube) was "welded" in place and wouldn't spin around the tube.  After the tube was removed, I took a little work to free up the nut, but we did it.
9.  Remove the air sensor and the air-stream check valve tubing from the exhaust pipe.
10.  Remove the exhaust pipe from the front of the catalytic converter. (Removal of the cross member skid plate makes this step easier, block the back of the transmission first, before removing the skid plate.) Sometimes, you may find it is also easier to remove the muffler and tailpipe mounts from the bottom of the body to gain more movement.
11.  Carefully clean off the old gasket residue from the block and intake manifold. This would be a good time to also remove and check the intake manifold to see if it’s warped. (Source of air leaks.)

Everything you’ll need should be removed at this point. Installing the new header is basically the reverse of the above steps.

12.  Install the hot air tube onto the headers.
13.  Insert the new headers generally into place.  (Meaning, don't bolt them in just yet!)
14.  Attach the intake gasket to the supplied header gasket. Then mount the two gaskets onto the block.
15.  The header and intake manifolds can now be bolted to the block. Follow the tightening sequence in your shop manual (basically radiating outward from the center).  One BIG advantage of the headers are that 11 of the 12 mounting bolts are easily accessible.  The one, number 3 in the tightening sequence, had to be reached from beneath the vehicle.
16.  At this point, the power steering pump mounting bracket, and power steering pump, fan belt, and alternator can be installed. (Thank yourself for taking careful notes!)
17.  Before going much further, attach the heat sink to the header pipe with the provided hose clamp (this is for the hot air intake flexible tubing to attach).

Assembled headers and carburetor!

18.  The carburetor, various sensors, vacuum lines, and electrical connections are ready to go back together. This is a good opportunity to replace any suspect vacuum line!

View of new insert location for Airstream Tubing.

19.  Once the headers are in place, you can now install the remaining piece between the headers and the catalytic converter. The only modification necessary is to shorten the air stream tubing to fit onto the mount on this remaining piece. A hack saw will due nicely here (measure twice, cut once).
20.  Attach the catalytic converter to the exhaust pipe, and tighten the two ends with the supplied stainless steel U-bolts. Then reattach the hanger bracket and muffler/tailpipe assembly if they were removed.
21.  Start it up and see if it works!