Whistle A Happy Tune
I've got an '86 CJ-7 with the 258. I just put the Mopar MPI kit on, and I love it-except for the whistling when I accelerate. What can I do? Will any of the extended air tubes and plenum chambers fit my CJ and could it cure the whistling, or do I have to put in a different throttle body with a tapered bore?
David Emery
Lubbock, Texas
If you're running an open-element filter, you're going to hear more throttle-body noise than if you're running a closed factory airbox. You should be able to rig up a TJ airbox under your hood with a little creativity. Just about any 4x4 shop in your area should have one it its dumpster, or you can look on www.craigslist.com.
You mention switching to a tapered-bore throttle body. If your throttle body is bored, the whistling is most likely coming from the Idle Air Control orifice window inside the throttle body.
You can remove the throttle body from the manifold and then remove the IAC valve from the throttle body. With a small die grinder or even a rat-tail file, make four evenly spaced notches on the top of the lowest IAC opening-it'll be the rectangular port just above the throttle-body gasket mounting surface. Don't get too carried away. The notches shouldn't be too deep (about the same depth as the serrations on a large steak knife) and try to space them evenly. The notches at the top of the port window should help break up the sharp edge that creates the whistling as air moves past the orifice.
Bag The Banger
I am a loyal Jp fan, read it every month, and love the tech articles. I am wondering if it is possible for you to stroke a 2.5L Jeep engine. I know...why do that when you can drop a new engine in? But I like my four-banger off-road and like the fuel economy on-road. I've searched the Internet far and wide and have yet to come up with a site that has done this. Is it possible, and how would I go about doing it?
Chris Skelton
Dover, Delaware
I built one of these motors on paper, then ran it through a desktop dyno simulator. It wound up making something like 20 hp over the stock 2.5L at a ridiculously high rpm. Low-end torque was worse than the factory engine at all speeds below 4,000 rpm. You needed a custom offset ground factory crank, custom rods, and custom pistons, and an expensive balance job using a lot of Mallory metal to keep the thing from shaking itself to death. By the time I was done, the engine build was somewhere in the $4,000-$5,000 range. It's just not worth it since the head doesn't really support any decent power levels. It is much more realistic to adapt a turbocharger to the 2.5L (check with www.505performance.com) or a supercharger (www.avengersuperchargers.com). Either of these offer much more power per dollar than trying to stroke the 2.5L.
Yet Again With The Dana 35
I'm 20 years old and a first-time Jeep owner. I'm currently in the Air Force stationed in Germany. I have been here two years and am going on my final year. Germany offers some very unique wheeling, but I can't wait to get back home to Texas and hit the mud. I would love to just buy a kit to upgrade to Dana 44s in the front and back, but with my pay, that may not be possible for some time. I was wondering if I change the gears in my rear D35, do I need to put the same ratio gears in the front D30? Also, if I add a locker in the rear, do I need to add one in the front? And is all this cheaper than going with a Dana 44 axle kit?
Zach Bingham
Spangdahlem Air Force Base, Germany
It's going to run you approximately $1,500-$1,600 to upgrade your Dana 35 rear. That's for the Superior Axle & Gear Super 35 kit (Detroit Locker and axleshafts), a new ring-and-pinion, and install labor. Yes, you do need to match the front gear ratio to the rear, otherwise you'll blow up your T-case because the front driveshaft will be trying to spin significantly slower than the rear. Figure it'll run you around $600-$700 for parts and labor to re-gear the front. When you change gears in the front axle you'll probably need to buy a new carrier since the Dana 30 uses a different carrier for 3.54-and-lower and 3.73-and-higher gears. A new open carrier will run you about $100, but you should be able to buy a used one out of a 4.10-geared Wrangler for next to nothing. Or you could take the opportunity to add a front locker if you think your wheeling will require it. However, to answer your question, you don't need to run a front locker if you run a rear locker.
As for going with the D35 or upgrading to a D44 in the rear, it really depends on your budget. You can now buy a complete, re-geared D44 TJ rear from Drivetrain Warehouse (www.4wheelparts.com) or 4WD Hardware (www.4wd.com). A TJ rear with the gear ratio of your choice, a Detroit Locker, and Alloy USA shafts go for about $2,099. Honestly, if you can swing the extra $400-$500, I'd absolutely forget throwing money at the Dana 35 and head straight for the Dana 44.
I really don't think there's any need to swap out the Dana 30 front in your Wrangler. The rear axle takes most of the brunt when off-roading. If you find you're breaking shafts or other components in the Dana 30, you can upgrade to alloy shafts easily at a later time, but I think your front axle will be fine.