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Engine Components - Inside Your Wrangler's Pentastar Heart

Written By: Louis Orellana

Shop Wrangle Internal Engine Parts

The need to take your rig's engine apart should ideally by for preventive maintenance, but sometimes catastrophe strikes and suddenly you have timing chain issues. Worse yet, perhaps you've thrown a rod. In either situation, if you're doing the work yourself, you'll want to make sure you have all the right parts and tools for the job.

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Engines found in newer Wranglers have come a long way from the early generation CJs. As Jeep continues to refine the Wrangler, the engine is a vital key to that advancement in performance and comfort. In this information guide, we’ll focus on Jeep’s Pentastar engine, which is found on late 2012+ JK models and the most recent 2018+ JL models. The guide will focus on some of the major internal parts of an engine and also offer advice on how to maintain these components, avoid severe damage, and when to upgrade or replace them.

Inside of a Pentastar Engine

The Pentastar engine is a 3.6-liter, six cylinder (V6), dual-overhead-cam (DOHC), 24-valve variable valve timing (VVT), gas powered engine. The engine was introduced to the Wrangler lineup in late 2011 within all the 2012 Wrangler models. The engine produces 285 horsepower and 260 lb-ft of torque. The engine is primarily constructed from aluminum and is 90-pounds lighter than the preceding 3.8L iron block engine found in earlier JK models. Internally, these are some of the major components found in the Pentastar engine.

Pentastar Engine Block & Maintenance

Engine block: The block is the structural foundation of the engine. Physically, it’s the bottom portion of the engine and houses the combustion chambers for the piston connecting rods and for some engines the camshaft. Once the cylinder head is attached, the piston’s up/down up/down movement results in combustion, which in turn rotates the crankshaft and ultimately the wheels of the Jeep. These explosions of energy create an intense level of heat requiring lubrication of oil, which is why the oil pan is located at the bottom of the engine block and utilizes a pump to help with the circulation of the oil through the passages of the engine. 

How to properly maintain an engine block: In order to maintain a properly functioning engine block, oil and coolant quality is critical to keep the block from overheating and the pistons from seizing within the chambers, causing catastrophic damage to the engine. A head gasket is also important to properly monitor and replace as needed, as it serves as the barrier between the cylinder head and engine block.

Upgrades to an engine block: An upgrade that can be done to an engine block is the boring or enlarging of the cylinder chamber and increasing the displacement of the engine. This allows you to run larger pistons and produce more power.

Pentastar Cylinder Head & Maintenance

Cylinder head: The cylinder head is the top half of the engine and the main portion of the engine where the combustion actually occurs. As the piston retracts it draw in fuel and air into the combustion chamber, when the piston goes up, it compresses the gases and a spark from the spark plugs ignite the fuel, resulting in an explosion that forces the piston back down to repeat the process. The cylinder head is the vital component to this delicately timed process, housing all the needed pieces for the combustion.

How to properly maintain a cylinder head: Due to the intense heat produced from combustion, the cylinder head requires the help of coolant and oil to maintain proper temperatures. Equally important to this process is the head gasket, which separates the head from the block. If the gasket is warped due to overheating, it could cause leaking of coolant and diminish the ability for the engine to operate at optimal temperatures.

Upgrades to a cylinder head: Common upgrades within a cylinder head are camshafts, which help with the overall valving of the engine. Upgrading the camshaft can help regulate the valving of the engine and in turn help produce more power and faster acceleration.

Pentastar Valvetrain & Maintenance

Valvetrain: The overhead valves found on the Pentastar engine serve the important function of opening/closing of the valves for the air intake and exhaust. They are controlled by the camshaft and the timing needs to be mechanically precise to ensure proper combustion and engine performance.

How to maintain a valvetrain: The same principles of heat and lubrication apply to the valvetrain. Normally the camshaft that controls the valve train is itself controlled by a timing belt. Pentastar engines, however, utilize a timing chain that requires very little maintenance or replacement.

Upgrades to the valvetrain: A valvetrain is normally upgraded with new valves when a camshaft is replaced. Both parts work in sync and require proper adjustment to function correctly.

Pentastar Connecting Rods & Maintenance

Connecting rods: A connecting rod is the arm the piston head is attached to. It rotates around the crankshaft during the piston's up/down movement.

How to maintain a connecting rod: Similar to the other internals of the engine, the connecting rod endures high levels of heat and stress. Rods can bend if the piston binds or if water enters the combustion chambers.

Upgrades to connecting rods: Connecting rods can be replaced with stronger and lighter alternatives to help assist with the rotational delivery of power from the engine combustion.

Pentastar Pistons & Maintenance

Pistons: Are the main source of power for the engine. Their flat-faced surface serves as the platform that absorbs the energy from the combustion explosion. Pistons are attached to the connecting rods and force the rod up/down during the combustion process.

How to maintain a piston: A piston is the internal part of the engine that receives the most amount of heat and impact. If the piston overheats due to lack of oil or lubrication it can seize in place. In addition, if water enters the combustion chamber the piston will try to compress the water (which can’t compress) and could shatter.

Upgrades to pistons: Pistons can be upgraded to stronger and lighter material. This in turn helps with the rotational force and distribution of power. Piston rings can also be changed to ensure proper sealing of the combustion chamber and help retain the most amount of energy from the explosion.

Conclusion

A Wrangler’s engine is put through considerable stress during off-road conditions and highway speeds. Ensuring all of these internal components are properly maintained and functioning at their maximum efficiency will help guarantee years of reliable and dependable performance. 

Fitment includes: 2012, 2013, 2014, 2015, 2016, 2017, 2018, 2019, JL, JK, Sport, Sahara, Rubicon, Sport-S