February 25, 2022

Considerations when modifying your diesel truck


Whether you’re buying a brand-new diesel truck off the lot or have a used truck, one of the first things people ask is what diesel mods I can make.

Maybe you want to power up for one of the diesel truck power events and see how fast it can fly down the dragstrip. Or perhaps you’re the pulling type, ready to max out torque to pull the sled. Some trucks work for a living, towing an excavator and a bed full of rock. Those same trucks may get to play, pulling a 30-ft. camper on a family vacation or a 28-ft. wake boat to the lake for splashy fun.

Whatever you may want to do with your truck, there are mods to make it perform better.

Keep in mind a diesel truck is a complex system made up of other systems. Turning up the boost without preparing the rest of the truck is like skipping leg day. When your 80-psi boost blows out the head gasket in a puff of smoke when the Christmas Tree goes green, everyone will see you skipped leg day. You took shortcuts and didn’t consider the head fasteners and gasket you need to contain that kind of power.

Before starting your diesel mods, you should understand the basics and develop a plan.

Top Considerations for Diesel Mods

The truck is a system made up of smaller systems. If you mess with one without considering how it affects the other systems, you could wind up with a truck that doesn’t perform like you wanted. You could also end up doing damage to the engine and yourself. When you boost engine power, consider the suspension and brakes. Consider changes to the torque curve – you might have more top-end speed but can’t pull as much as fast as you’d like. If one system overpowers the others, you could be disappointed in the results.

Boosting Power

Three factors contribute to engine power with a diesel engine: air, fuel, and compression. These three elements must work together in the right proportions to produce efficient horsepower. If these elements get out of whack, your engine could be down on power, overheat, or use a lot more fuel.

Increasing Air Flow

Airflow is one of the areas where the system approach is essential. Pumping more air into the engine by adding a turbo or bumping up the boost will increase the capacity for horsepower. A cold air intake is an affordable early mod. Cold air compresses more easily so more air can flow into the intake. A high-flow air filter and larger intake ducting can smooth airflow to the engine. Look for intake systems that work with the factory tuning so your truck can hopefully remain street legal. An intercooler upgrade can help maintain the boost pressure after the air leaves the turbo and flows into the combustion chamber, making the turbo more effective.

As you increase air flow, don’t forget about the exhaust. If you’re drawing more air into the engine, you’ll have to pump it out. A high-flow exhaust should be one of the first mods you make so the engine can breathe better, according to Diesel Tech magazine. Stock exhausts restrict airflow for a number of reasons, including noise reduction and reliability. Exhaust mods are more complex in late model trucks with a catalytic converter, Diesel Particulate Filter (DPFs) or a urea injection system. For street-legal trucks, it’s best to follow federal and state regulations regarding these devices.

Increasing Fuel Flow

For more fuel flow, upgrade the fuel pump and injectors to match the increased airflow from your mods. Factory injectors are designed for fuel economy, not power. If you’re upgrading the fuel injectors, match them with a comparable fuel pump to meet the demand. Fuel system upgrades are one of the first things to consider to increase horsepower significantly, according to Rush Diesel Repair.

Increasing Compression

Diesel engines compress air at a ratio of around 14:1 up to 25:1. A higher compression ratio leads to better efficiency and more power.

You can increase the compression ratio in many ways, including tweaking the engine control module (ECM), resurfacing the engine deck, using a thinner head gasket, changing valves and pistons and other wizardry.

A performance camshaft can help increase the compression ratio by allowing more air into the inlet valves. The camshaft lets the engine gulp more air by leaving the valves open longer, with a different lift and profile than the OEM spec version.

Flashing the ECM

With an ECM flash, you can tune the parameters for the engine and transmission. You can adjust timing and pressure for more horsepower and change transmission shift points. As you improve the air intake and exhaust, your engine can handle more fuel. Plug in an aftermarket tuner to dial in a more aggressive fuel map so the turbo can spool quicker, adding up to even more power.

Read Also About: How to Care For Your Diesel Motor

This is another system of systems area. If you get this wrong, your truck may not pass an emissions test or could blow up. Installing a tuner will allow you to tweak for best performance as you continue to modify your vehicle. This is a mod often best left up to an expert.

Upgrading Engine Components

Most stock diesel engines are over-engineered and overbuilt, which is why it’s not unusual to get several hundred thousand miles out of one. But if you’re seeking asphalt-shredding levels of power for some form of motorsport, some of the engine components should be upgraded accordingly. Consider strong connecting rods, pistons, crankshafts and other vital components that will have to absorb the power from your creation.

Depending on your build, you may have to upgrade your torque converter and/or the entire transmission. Your transmission should have a label indicating the maximum allowable torque. If you’re going beyond that, it’s a good idea to make sure the transmission can handle the load.

Upgrading Handling & Suspension

Your truck should look as good as it runs. Plus, the rest of the truck should be prepared to handle the power your engine mods are putting out.

Lifting and leveling kits will change the stance to reflect the rockin’ engine under the hood. Plus, if you’re prepping for the strip or pulling a sled, you need to be able to put the power down where it belongs.

You may need new wheels and tires as well. They say clothes make the man. Well, rims make the truck. You wouldn’t put on your finest weekend outfit and wear your workboots. Let your rims reflect your personality.

A wise man once said, don’t skimp on things that come between you and the ground, like shoes, mattresses, and tires. While rims may not matter much in terms of performance, it’s worth ponying up for quality tires that match what you want to do with the truck.

Consider Cylinder Head Gaskets

Head gaskets are often blamed for an engine failure, but it’s usually not the gasket’s fault. It may have been installed incorrectly when putting the engine back together after mods. A head gasket is relatively inexpensive in the grand scheme of things, so it’s a good idea to use a new one, especially if you’ve made engine modifications, Engine Builder magazine reported.  If you’ve had the engine block decked, you may need a thicker gasket to maintain piston clearance. If you’re boosting the cylinder pressure, the stock gasket may not be able to handle the load. After you’ve made engine mods, check the piston clearance to avoid any interference.

Replace Factory Head Bolts with Head Studs

After making your mods, replace the factory head fasteners with head studs when you’re putting the engine back together. OEM head fasteners are prone to stretching under increased combustion pressure and temperatures. That could lead to head gasket leakage which can cause a host of problems.

The head gasket contains the combustion pressure to generate compression in the engine and allows the oil and coolant to flow through the block. It requires even clamping force across the cylinder head to work properly. Head fasteners stretching even a few thousandths mean the gasket could leak. If you’re running drags or pulling the sled, you’ve seen the plume of smoke when a head gasket goes.

Like we noted above, the head gasket isn’t really the problem. The fasteners have failed because they were not strong enough or not installed properly. It’s critical to follow the instructions for torquing the head fasteners.

OEM bolts don’t fare well under boosted power, and if you’re adding a sequential turbo or running nitrous oxide, you’re entering the danger zone.

High-performance head studs are engineered to withstand the pressure of a modded diesel. Plus, the stud design with nuts makes it easy to remove and replace the head without replacing the fasters every time. Cylinder head studs can eliminate the problem of head lift when the engine is under load.

If you’re working on a diesel engine mod, take a look at Tracktech Fasteners®. These high-performance head studs are engineered and manufactured for applications where horsepower exceeds the OEM specs. They’re tested in the lab and on the track to give engine builders peace of mind.

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