Insane Inline II Jeep 4.0 I6 - Jp Magazine

Pete Trasborg Brand Manager, Jp

Way back in the August '05 issue, we set out to build the biggest, baddest inline-six Jeep engine the world had seen, by December '05 it was finished in more ways than one but the urge to build a huge Jeep six-cylinder never left us. We felt we owed it to our readers to put down some big power with a Jeep engine.

custom Jeep Inline 6 Engine block Photo 26051864

After decking the engine 0.015 inches, the block was then bored about 0.060 over to bump the bore up to 3.937-inch. Many engine builders don't hone the block and then check runout from the top to bottom of the cylinder. Zach at 505 does, and for this build the company made sure that there was 0.0005-inch or less variance so the piston rings seal the same throughout the cylinder.

This time around it started with a press release from 505 Performance regarding a 5.0L stroker kit for the 4.0L Jeep engine. There is no replacement for displacement, after all, and a quick phone call to the owner of the company, Zach Steele, had us convinced we'd found the builder of the next Insane Inline. So, working together with Zach at 505, we put together what might be the most powerful Jeep inline engine ever.

Take a 5.0L Jeep engine and put a turbo on it, and you are in for a good time, no matter what happens. On this one, we decided to shoot the moon: we are invading NASCAR territory with two-horsepower per cubic inch, which even in these modern-day horsepower wars is unheard of for a street-driven vehicle, much less a Jeep.

To get to that goal, we've taken every little step we could to squeeze every last pony from this engine and we are going to share the tricks and tips that we picked up with you for your own engine build. Some have said we are optimistic, some have plain said that we are off our rocker, but we are going to tweak the internals and lean on this motor until we get to the 2hp per cylinder, we blow it up, or we prove that its just not possible without nitrous. So, jump in and sit down, this is going to be a great ride.

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The Ross Racing pistons (124199WF) were coated with NIC Industries C-186 Piston Coat by Streamline Custom Coatings to help reduce detonation. We went to Streamline for all our coatings on this engine because of its high level of craftsmanship and attention to detail. Streamline also coated the piston skirts with NIC's C-110 Microslick coating to reduce friction, and protect the cylinder walls and pistons in case something goes wrong and contact occurs. Also shown are the Ross Racing wrist pins (PN 927-07-25) and Sprio-Loxs (PN 4004-D) as well as the Clevite bearings and Eagle ESP H-beam rods that are included with the upgraded 505 Performance 5.0L stroker kit.

With an engine that is being built to handle up to 30 pounds of boost the piston rings become one of the most important parts in the motor. If you've gotten your cylinder walls perfectly parallel as we have, the only other variable becomes the piston rings. We used Total Seal Custom rings (1.2-, 1.5-, and 3.0-mm widths) and file-fit them per the specs that came with the very thorough install sheet. The trick is to have some space between the end of the ring so that as it heats up it has room to "grow," but not so much space that the added pressure the turbo is pushing into the combustion chamber pressurizes the rest of the engine.

If you've taken good care building the engine, the only thing left to chance is the oil. A few years ago, oil manufacturers drastically reduced the amount of phosphorus, zinc, and other additives in our oil. The additives that were killed meant that our flat-tappet Jeep engines started eating camshafts. This Amsoil Dominator Racing Oil (15W-50) has more additives than regular oils used to have and great shear characteristics. In an engine this gnarly and expensive, it doesn't pay to take chances on running cheap oil. A high-volume oil pump is recommended for this kit, but none were available at the time. So, this oil pump is a Mopar pump that we got from Summit Racing which 505 Performance then had to modify so it would crank out more pressure.

We started with a bare head from Alabama Cylinder Heads and then 505 spent a ton of time blending the bowls, removing casting ridges and so forth. Everyone talks about "porting" the head, but many Jeep owners mistakenly think that it is important to port the area where the intake and exhaust manifolds bolt up. While there might be more power available from gasket matching, most power found through porting comes from the area right behind the valves. We went from the stock flow number of 209cfm (right) to moving 298cfm (left) which will translate into better power later.

Here you can see the 5.0L forged crank installed in the block with no grinding needed. Thanks to the special combination of crank, rods, and pistons, you could put this kit in your 4.0L block at home. An upgrade we went with was this girdle which Chrysler installed in later Jeep engines. We found a used one to add to our motor, and then found out they are available as a kit from 505 Performance as well (including new studs and nuts for mounting). The girdle stiffens the bottom end of the block when under load and helps keep the main bearing caps better aligned for less wear on the lower-end bearings. With the power levels we were shooting for, every little bit helps, but the girdle would also likely increase reliability of a lesser-built engine as well.

As for keeping the fluids where they should be, we went with Fel-Pro for almost every gasket in the engine. We just got the full rebuild kit (HS 9076 PT-1, HS 9076 PT-2, and HS 9076 PT-3) to put it all together. The only thing we were worried about was the boost pressures, but 505 already had a solution to that. The pistons were setup with a 0.010-inch positive deck height to save the head gasket from the boost and the ignition cycle. Coupled with that is the MLS head gasket upgrade which is comprised of multiple steel layers that greatly prevents the head gasket blowing out.

With all the machining we did on the head, we could have used a stock head, but the fact is we weren't about to magnaflux a junkyard head to make sure it wasn't cracked before we started machining. The cast-iron head from Alabama is reasonably priced and includes thicker webbing in the mid-section of the head where the stockers tend to crack. We had Streamline coat the combustion chambers and 505-sourced Ferrea LS1 valves (2.00 intake/ 1.550 exhaust) with the C-186 Piston Coat to further reduce detonation. On the right are the stock valves (1.908 intake, 1.50 exhaust).

We went with a regular flat-tappet cam with solid lifters for this engine. Shown here is a 505 Performance cam kit. You could use a kit similar to this for the engine in your Jeep now, but our cam was custom-ground with a single-pattern 232 @ 0.050 duration and .478 lift on a 114-centerline. The cam is tailored to take full advantage of the turbo, allowing lots of air in and minimizing overlap to maintain cylinder pressure under boost. Included in the cam kit are the cam, lifters, valve-springs, valve-spring retainers, custom-built cam button bolt, custom-length pushrods, and a big-block Chevy-sourced roller-chain timing set.

Another important step in putting the engine together is to degree the camshaft. The cam determines when the valves open and close, thereby controlling when the fuel/air mixture goes into the chamber, and when the spent exhaust gasses go out. In the 4.0L, the distributor is also spun off the cam and tells the computer when to fire the spark plug, so it also effects when the mixture burns. Get it in there too early (lighting the flame when the piston is still coming up) and you can damage parts. Get in too late (when the piston has already started going back down) and you won't be making the power you could. Degreeing it is the only way to make sure you are dead-on. All of 505's engines are degreed before getting the head bolted on, and ours was no exception.

Any time you make more power, you will be creating more heat. So, we turned to Hesco for its world-renowned high-volume water pump and high-volume thermostat housing to move just as much water as possible to keep this monster as cool as it can be. We say world-renowned, because the Hesco impeller design works so well, that Jeep actually used it in the '01-and-up Wranglers.

The adjustable Yella Terra 1.6:1 roller-tipped roller rockers, PN YT6328, increase lift from 0.478 with the stock 1.5:1 rockers to 0.510-inches. The needle bearing, roller fulcrum means less friction to move them, freeing up more ponies. In addition, the roller tips not only provide less friction, but by rolling across the valve stem, they wear less too.

Sneak Peak
Here's a shot of the engine on the dyno at Westech Performance. We ran out of time and space in this issue so you'll just have to tune in next time for the parts we bolted to the outside of the engine to finish it off, and for the insane power numbers we laid down. We can tell you that before any real tuning, we are already really close to our power goals, putting down 558hp and 674 lb-ft. To see how we got there, and how much further we push it, tune in next month.

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Insane Inline II Jeep 4.0 I6 - Jp Magazine

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