Category: Heavy Duty Kits


Anti-polishing rings is know by different names lik:

1. carbon scraper ring

2. piston cleaning ring

3. bore polishing ring

It is a newer development in Cummins ISX engines where a cylinder liner will have an anti-bore at its top that holds a ring insert.

Explained in Following Picture:

Anti-Polishing Rings Functions:


Like most engine design changes, the development of an anti-polishing ring was created with a particular purpose in mind. In this case, that purpose is removing carbon buildup from the piston. Looking at the diagram above, you will notice that the ring insert protrudes slightly from the interior cylinder wall. Because of its protrusion, it comes into close contact with the topland of the piston. This close contact doesn’t allow for even the slightest bit of space between the piston and the ring, meaning the ring will scrape away any carbon that would otherwise accumulate on the piston (which is why some people call it a carbon scraper ring).

Benefits of Anti-Polishing Rings”


By preventing carbon buildup, the ring also prevents liner polishing (which is why it’s also called an anti-polishing ring. Cylinder walls are made to have peaks and valleys, and there is a particular bore surface finish that allows the engine to run its best. Engine Build Magazine has a detailed explanation or various cylinder bore surface finishes if you’re curious to know more about that. When there is too much carbon built up on a piston, the carbon slowly files down the peaks of the liner wall. When these peaks are worn down enough to almost eliminate the troughs of the liner will, it is known as bore polishing. Bore polishing can lead to many serious issues.


The most common issue that bore polishing leads to is an increase in oil consumption. It is natural for an engine to consume some oil. But if you notice that your engine seems to consume oil excessively, try using Cummin’s oil consumption evaluator tool.


In addition to oil consumption, bore polishing can also cause DPF regeneration, increased oil filter flow, plugged oil filters, and sticky VGT actuators. None of these are good for your engine and can cause you a lot of money if not taken care of. The benefits of getting anti-polishing ring cylinder liners are that they are proven to dramatically reduce the chances of these problems occurring.

Anti-Polishing Rings Compatibility:

If your ISX engine has heavy bore polish due to carbon packing, Cummins recommends you replace your current liners with APR liners ASAP. However, if you choose to upgrade your liners, you need to make sure everything is compatible first. Below are some compatibility points to be aware of when getting APR liners:


APR liners must be used with certain pistons.


They cannot be used with open skirt pistons.

They cannot be used with high top ring pistons.

They must be used with closed window, reduced diameter, low top ring pistons.


All six cylinder liners must be the same.

Liner shims must be replaced with new shims upon installation.

Perhaps the easiest way to make sure everything is compatible when you upgrade is to buy a complete engine rebuilt kit. Our techs will make sure you get everything that you need to switch your engine to APR. Check out our APR offerings here.

Anti-Polishing Rings (APR) Piston Installation

Piston installation can get a little tricky when you have an APR cylinder liner. So, let’s go in order.

First, the good news is that you can usually remove the anti-polishing ring by hand. If you have a difficult time removing the ring by hand, there is a snap rings tool that will help. The rest of the disassembly process should be the same as with any other liner.

The process gets tricky when you go to install the piston assembly. Because of the nature of the anti-polishing ring, you won’t be able to install the piston from the top of the liner. Therefore, you can only install the piston assembly from the bottom, unless you install the anti-polishing ring after you install the piston. You will also need a piston ring compressor adaptor tool to do the installation.


The Duramax engine is one of the finest ever to have been made for pickup trucks. But even the best can have a few faults. The original Duramax engine that rolled out back in 2001 and every variant that rolled out in the subsequent three years have a serious flaw. The fuel injectors are not among the sturdiest. The injectors have a substantial chance of failing, much before a hundred thousand miles. Should the LB7 injectors fail, they can leak substantial amount of fuel and dump it into the engine. This can happen when you are driving but also when your truck is idle. If the excess fuel leaked doesn’t get burned, then it can affect the oiling system and the engine will start to get filled with diesel. That is definitely not something you want!

While GM has offered an extended warranty to cover up to two hundred thousand miles, the injectors failing can be a bummer! LB7 injectors are pricey and they cannot be replaced unless one is very well trained. The injectors are so hard to reach that most people wouldn’t even be able to get to them, much less replace them.

When should you replace Duramax LB7 Injectors?

You must be observant of signs that your LB7 injectors have failed or have worn out. You may notice white smoke. Be careful because white smoke can also be a symptom of coolant loss or oil seeping into the radiator. But usually, white smoke is considered to be a cause of LB7 injectors’ failure in Duramax engines. Get your truck to a technician and one can test the balance rates of the injectors to know for sure if they must be replaced.

How to overhaul or replace Duramax LB7 Injectors!

First, the intake has to be removed. Then one must remove the fuel filter along with the housing and lines. One would then get access to the valve cover. The fuel injection control module has to be removed. It is typically mounted on the valve cover at the passenger side. There are several electrical and rubber connections that must be removed. Then you would get to the injector line. Take out the lower and upper valve covers and you would have access to the injectors.

The next steps involve removing the electrical connections, taking out the injector return line and then removing the injectors. You may need an injector puller for the job. Once the injectors in need of replacement are removed, new ones can be installed.


The John Deere Power-Tech PSX 6135HFC95 is an inline six-cylinder 13.5L (824ci) diesel engine capable of generating 617 horsepower at 1,900 rpm and a torque of 1,962 ft-lbs at 1,600 rpm. With a 5.20×6.50” bore and stroke, single overhead camshaft, valve train with four valves per cylinder, a compression ratio of 15:3:1, a sequential fixed and variable-geometry turbochargers induction system, electronic unit injection at 33,000 psi and air to air inter cooler, this engine is in the forefront of diesel technology. The engine requires an oil change every five hundred hours. The head material is cast gray iron alloy while the block material is cast gray iron. The crankshaft material as well as the camshaft is forged steel. The engine is just over five feet in length and a tad more than three feet in width. It is five feet high and weighs 3,699 pounds or 1,678 kilograms. The engine has a cooled exhaust gas re circulation system, diesel particulate filter and oxidation catalyst as its emission system. It complies with the emission norms of EPA Interim Tier 4, CARB and EU Stage III B.

What stands out in the engine is the low-pressure fixed turbo and a high-pressure variable-geometry turbo working in sequence, the one-piece cast design using a heavy-duty, gray iron alloy material, the high-carbon steel camshaft with induction-hardened lobes to reduce noise and to increase life and the full-floating steel pistons with crankshaft of high carbon forged steel that can resist extreme heat and offer precise alignment. The attention to detail makes this engine a wonder.

Modern emission standards have been getting stricter by the day. Power or high performance is thus an expensive or an elusive attribute. The Power-Tech PSX 6135 smartly uses a cooled exhaust gas re circulation, a powerful injection system, a substantially large diesel particular filter and a diesel oxidation catalyst to adhere to the emission standards. The 13.5L Power-Tech PSX 6135HFC95 is a victory of industrial design and engine architecture. It is needless to say that the engine has already found numerous takers in the world of fire pumps and oilfield drills.