Gauging Engine Data - Engine Builder Magazine

Gauging Engine Data

Gauges not only provide vital data about your car or truck's engine, but can also add some style to the vehicle. There are many different routes to take and angles to consider when deciding on what gauges to add to your vehicle.

Over the years, I’ve developed a skill for weeding out the good garage sales from the bad. First and foremost, if it’s in a development that was built in the past 20 years, I keep on driving, there’s nothing there for me.

It’s the old houses with the old garages that bring me in. Most of the time there are tables set up in the main part of the garage filled with the almost prerequisite boxloads of coffee cups, stacks of VHS tapes and at least one never used electric carving knife, but it’s the shelves on the walls that contain disorganized collections of the random stuff that is valuable to the automotive crowd.

This is where I concentrate my search for treasures. Among them I often find old automotive gauges and I’ve been snagging them when I can for a few years now. Sometimes they are lone gauges, sometimes a double or triple set; you never know what you might find, but foresight has been paying off with this round of collecting other people’s junk.

Different performance applications require monitoring different aspects of the engine. However, water, boost and fuel are three very common gauges to utilize across the board.

Gauges are always a fun topic, and they are key to the function and personality of a car. This month we’re going to take a look at some of the most common ones and the most common features, starting with old school and onto up and coming trends.

Hoo! Looks good on my end. Sometimes part of a restoration and sometimes an upgrade in the eyes of the vehicle owner, more and more classic vehicle owners want this type of gauge and in many cases need help to figure out if they will work. Examples of “Old School” include vintage Sun Blue Line gauges or perhaps vintage Stewart Warner. We’re talking real vintage, not just the look or a line of new gauges in this case, but the actual old pieces.

Most of the time the vehicle owner has seen old pictures of a certain muscle car or race car and is trying to get everything period correct. They are usually looking for an exact brand, size or specific color, and in some cases, they might already have the gauges they want, but need a professional to install them.

Mechanical gauges are always a straightforward hook up, but electric has its advantages with more options for creating a clean engine compartment. The problem with electric on these old gauges is that many of the ones you find are missing their respective sending unit or control box.

Thanks to this type of period-correct look and its growing popularity over the last few years, it is becoming easier to find sending units and parts for these gauges and some are being reproduced as well. There are also electronic specialty shops that can repair or make these gauges work, and this is especially helpful when using a vintage tachometer with a modern ignition system.

The internet is the best tool to track down the parts or people that you need to make these vintage pieces work.


Old American Iron is as hot as ever when it comes to restoration and there are two common paths to follow here. One is a typical restoration where the car is built to look original, but since the owner is putting a lot of money into their engine, they want to make sure they are keeping tabs on it. A tachometer, oil pressure and water temperature gauge are the big three with these traditional types of restorations and aside from each of us having our own individual taste for the look of them, no frills is usually the choice, with electric or mechanical being the only other decision.

The other path is the Restomod, which opens a lot of options in the gauge category. The look and style of the gauge is the choice of the car owner and there are gauge bezels and custom dashboard kits for many of the popular classic American cars and trucks. Digital is also a popular choice and ultimately the options can seem endless.

The common Restomod way of thinking leads to a full set of matching, modern gauges including oil pressure, water temperature, voltmeter, fuel gauge, tachometer and speedometer.  

Since the import segment of the market is heavy into computer tuning, air/fuel ratio gauges are also commonplace. Some of these air/fuel ratio gauges also include built-in safety features that allow them to cut boost using pressure references or by recognizing a lean air/fuel condition.


The import scene leans in a little different direction compared to the classic American side. Most of these cars are equipped with tachometers from the factory, so it’s not a common add-on, but the big factor is that turbocharging has been a driving force of import performance for a long time. In the world of gauges, the boost gauge is king for these cars. Digital or analog are available and “pod kits” are also a common accessory for a clean mounting.

Oil pressure gauges are frequently installed, and since this segment of the market is heavy into computer tuning, air/fuel ratio gauges are also commonplace. Some of these air/fuel ratio gauges also include built-in safety features that allow them to cut boost using pressure references or by recognizing a lean air/fuel condition.

Pyrometer (exhaust gas temperature) gauges are also common additions to turbocharged engines, and last but not least in the import category, is gauge color. Dash design is clean and functional from the factory and keeping it that way is important to these vehicle owners. Many gauges come with color options that are specifically designed to match the factory markings as well as backlighting.


Those involved in motorsports rely on their gauges in a much more serious manner than those of us cruising the streets. There is a lot more at stake for the serious racer and knowing what your car is doing at all times is a crucial part of the equation.

Gauges aren’t bought for looks or style; function, dependability and accuracy are at the top of the list. Weight is a factor, though it might not be much, every little bit counts. Visibility is always an important factor and light-colored gauge faces with bold black lettering are one of the more common choices.

Some forms of motorsports, especially in the off-road arena translate into a rough ride where the vehicle is subjected to heavy vibration and constant pounding. For these extremes, fluid filled gauges dampen the movement of the needles.

Ultimately there is a gauge for just about everything a racer could need and which ones they need depend specifically on the type of racing as well as the type of induction or power adders they are running. However, the top three that cover racing as well as almost any type of street car are the tachometer, oil pressure and water temperature gauge.

Few may dispute that the tachometer is the central and most important gauge for any type of racing, and popular features for serious competition include a large visible shift light and memory recall.

When oil pressure gauges near the top of the line they feature programmable warning lights, peak recall and output accessory control, all of which can be of critical importance for a race car driver.

Rounding out the top three is water temperature and as with oil pressure they can include warning lights and peak recall features.


When it comes to performance diesel applications, mountains of torque and horsepower are being cranked out, so there’s a lot to keep tabs on. Boost pressure gauges are hot on the list and their primary importance is to monitor for either an over boost or under boost condition. There’s always the question of mechanical or electronic when deciding on gauges, but electronic is the recommendation from a lot of truck builders for boost gauges. Excessive length, bends or kinks in the mechanical line can alter the reading of a boost gauge and going electric eliminates this possibility.

EGT (exhaust gas temperature) gauges are another common addition and also one of the more important gauges. Turbo diesel engines can suffer severe damage at the hands of excessive exhaust gas temperatures and when you’re pushing these to the limit, it’s a reading you want to keep an eye on.

Fuel pressure is critical on modified diesel engines and can have an effect on fuel efficiency, throttle response and overall performance. For those reasons, fuel pressure gauges are another popular choice.

Transmission temperature gauges are almost a staple of modified diesel trucks and arguably one of the most important. The transmission is first in line to take the brunt of abuse from the engine and overheating is the primary cause that shortens or ends the life of an automatic transmission.

A transmission temperature gauge monitors the temperature of the fluid, and over time, if the temperature begins to average a higher reading, it can be an indication that the fluid needs changed. One of the most important functions of the transmission fluid is to transfer heat and cool the transmission. Old, worn fluid can break down and lose efficiency for this process.

Rounding off the diesel list is a differential temperature gauge. Not as common in the past, the stress put on the differentials of these trucks is greater than it has ever been in the past. Especially if you are towing long distance, keeping an eye on differential temperature is the best way to know you’re not going to experience premature wear or differential failure.

The bottom line for gauges? If you need to keep tabs on it, there’s a gauge that will get the job done, in whatever style you are looking for. EB

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