The Scrambler/Overlander Project:
Engine and Drivetrain Upgrades
After replacing the original engine with a new long block, I made two significant upgrades - a conversion to fuel injection using a Howell kit, and GM HEI distributor using junkyard parts. I highly recommend both upgrades.
The Howell kit does not include an air cleaner, and the Howell manual recommends an open-element air cleaner. When I initially did the install I used an open-element as recommended, but I really didn't like the noise from the throttle body that an open-element allows, and I felt that the open-element being directly above the exhaust manifold would be drawing excessively hot air into the intake which would negatively affect performance.
I wanted to use an air cleaner box from a current model TJ, but the current model has a much smaller throttle body opening than the General Motors throttle body. So I bought the following parts on eBay - on the left is a used complete current model air cleaner box and connecting tube. On the right is a custom air cleaner kit designed to fit a General Motors truck with throttle body fuel injection.
Of the kit on the right, the only part I used is the "snail" - the plastic housing that goes on top of the throttle body. I cut off the end of the Jeep TJ air tube, and adapted the snail's 3" output to the 2" air tube using a 3" to 2" rubber adapter found in a plumbing supply store. The TJ air box mounted fairly easily to the inner fender - I did have to make a few "dimples" in the fender to match the contour of the air box so it mounted properly. I re-used the CJ's bellows hose to go from the air box to the grill, to do this I relocated the hose flange from the driver's side to the passenger side, and I added a second flange on the air box.
I highly recommend using some type of air cleaner like this instead of the open element recommended by the Howell manual. The engine definitely runs better drawing the cooler air, and is also quieter under acceleration.
One other suggestion about doing the Howell conversion - the conversion requires the same wiring change to bypass the original engine computer that the so-called "Nutter Bypass" does. I did the Nutter Bypass the weekend before starting the main EFI Howell conversion. By doing that I eliminated one variable from the main conversion. And by the way, the Nutter Bypass made a huge difference in the performance of my Jeep - which I take as a sure sign that the emissions system was not working properly. In New York State, though, this modification isn't street legal, as I'm sure is the case in other states as well.
Since the above photos were taken I've also upgraded the alternator to a late model 108-amp GM CS-144 type, and I've replaced the mechanical fan with a Ford Contour high-performance dual fan controlled by a DC Control FK-35 electronic fan controller. both were fairly straightforward and simple upgrades and well worth doing.
With my 31x10.50 tires, 5th gear was pretty much useless and performance was generally slugish, so it was really necessary to get rid of the stock axle ratio of 2.73:1. I found a good pair of complete 3.54 axles and swapped them for the 2.73's. Now I can cruise easily on the highway at 65 in 5th gear, and take on all the big hills in my area in third gear.