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October 2006 4x4 Tech Questions - Techline

Posted October 1, 2006

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Question: I pulled an AMC 360 with a TH350 tranny out of a '72 Jeep Cherokee. I'm going to rebuild the 360, and put them both in my '80 Jeep CJ-7. Since the TH350 was made to go in a Jeep vehicle, will it need an adapter to mate up to the Dana 300 transfer case that's in the CJ?
Charlie Janek
via fourwheeler.com

Answer: To start with, the transmission you have is a TH400, not a 350, as Jeep only used the 400 version of the GM automatic transmission. In fact even the little V-6 used this transmission.

Yes, you will need an adapter to the Dana 300 transfer case. Novak has one under PN 134 (www.novak-adapt.com).

Just as a note for those who are contemplating this same swap using a '76-'79 Jeep TH400, the Novak people tell me that this Jeep TH400 is a bit different and takes a special adapter. These later transmissions featured a special tilted transmission-case casting. This adapter configuration is unique on the market in that it levels the adapter's base foot for square mounting on the rear isolator mount and crossmember. This is useful in that the adapter allows installation without clocking your transfer case downward, or having your transmission mount sit crooked. The identifying feature of different transmissions is that the earlier cases such as those used from (I believe) '69 to '75, used a special adapter ring between the engine block and the transmission.

Question: I own an '00 Cherokee and am installing a Borla exhaust-header to tailpipe. I was wondering what your views are on heat wrap on the headers to keep the heat away from the intake. I understand it voids most header warranties and was curious as to the cons of doing such.
Jon Whitney
via fourwheeler.com

Answer: Heat wrap works excellent on drag-race vehicles-not so much to keep heat away from the intake, but to maintain the heat in the headers. Hot air, as in exhaust gases, flows faster than cold air, and therefore exits faster. Sometimes, it's used where necessary to keep heat away from other components, or in the case of engines like your 4.0 six-cylinder where the intake and exhaust manifolds are on the same side, to keep heat away from the intake. Would it help performance? Yes, maybe a bit-but not so much that you would notice any by the seat of your pants.

Now for the bad about it: Harsh environments like those experienced off the highway, especially mud and water, will not only destroy the wrap, but worst of all can cause damage to the exhaust system under the wrap. Moisture will collect between the metal and the wrap in the form of condensation when the motor is shut off. Yes, stainless steel headers, like the Borlas, resist corrosion a lot better than painted steel, but it still will happen. Another problem-and perhaps the worst one-is that excessive heat can build up in the area of the wrap and cause the tubing to "burn out" in that area. Drag racers don't really have this problem as their run time only amounts to a few seconds, while on your vehicle the heat will be held in for perhaps hours at a time.

I really suggest that you forget the heat wrap. The Borla headers are a great choice. I have used them on three different Cherokees and found that they're an excellent product. They really allow the engine to come alive and not only make more horsepower but seem to allow the engine to pick up rpm a lot quicker.

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