The torque wrench is quintessential to building horsepower. I know this may sound a little odd and be a stretch, but stay with me. Recently, the ½” ACDelco ARM303-4A digital angle torque wrench made it’s way into our hands here at Shop Tool Reviews. As normal, we did our best to give it the professional shake-down.

Back In The Day

I remember the torque wrench (no, not a torque wrench, but the torque wrench), it lived in a wooden box inside a special drawer in the toolbox. If my brother or I touched it, we would surely be tarred and feathered, or worse! The torque wrench was like a magic wand when Dad would dial in the correct measurement, lock the handle, then systematically and sequentially tighten the correct bolts. It was so cool when it would reach the correct torque, then resound the slight “click”.

Torque Wrenches

In days past, the torque wrench didn’t come out of the toolbox until you were rebuilding a motor or replacing a head gasket. Today’s vehicles have more technical fasteners than ever before. From lugnuts, to head bolts, to valve covers, there is a plethora of opportunities to use your trusty torque wrench. Take your pick, you can probably find any area on the vehicle where the manufacturer recommends some sort of measured force for the fastener.

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Furthermore, the typical beam or click-type torque wrench won’t successfully meet protocol anymore. The critical fasteners in engines today require more than just a measured clamping force (ie. Ft-lbs., in-lbs., N-m, Kg-cm). Critical fasteners, such as head bolts, rod bolts, main cap bolts, etc. in current engines are considered Torque To Yield (TTY) fasteners. In addition to torqueing the fasteners to xx ft.-lbs, you have to also tighten the bolt further measured in rotational degrees (angle). This angle measurement is one of the great features the ½” ACDelco ARM303-4A digital angle torque wrench brings with.

Torque Specifications

To get a better understanding, let’s take a look at just the cylinder head bolt torque specs from the old world and today.

Generation I Small Block Chevy

The Gen I Chevy small block was made from 1955 until the 1990’s and was in everything from corvettes, impalas, trucks and about any other mid and full size vehicle Chevy made. It’s arguably one of the most used motors of all time. The small block ranged from 265 cubic inches to 400 cubic inches. The torque specs and sequence for the Gen I small block were as follows:

1. Cylinder Heads: 65 ft-lbs.

Pretty simple, set your torque wrench at 65 ft-lbs., tighten, and you were done. Easily attainable with your standard beam or click-type torque wrench.

Generation III Small Block Chevy – LS Series

The Generation III Small Block Chevy is more commonly known as the LS series. The LS started production in 1997 and is still the workhorse of all GM products today, from trucks to cars and supercars. The LS ranges in size from 4.8L to 7.0L displacement. The rotating assembly and parts of the old and new small block don’t differ in a lot of ways; however, the torque specifications between the two are miles apart.

1. First Pass – Cylinder Head Bolts: 22 lb-ft
2. Second Pass – Cylinder Head Bolts (All M11 Bolts in Sequence): 90 degrees
3. Final Pass – Cylinder Head Bolts (All M11 Bolts in Sequence-Excluding the Medium Length Bolts at the Front and Rear of Each Cylinder Head): 90 degrees
4. Final Pass – Cylinder Head Bolts (M11 Medium Length Bolts at the Front and Rear of Each Cylinder Head in Sequence): 50 degrees

This would not be achievable with just your standard torque wrench alone, hence you would need an angle adapter or have the ½” ACDelco ARM303-4A digital angle torque wrench.

Measurement in Degrees of Angle

Subaru Impreza 2.5i

Just to give another example of TTY cylinder head bolts. This is from the Subaru Impreza 2.5i.

1. Torque: 22 ft-lbs.
2. Torque: 51 ft-lbs.
3. Loosen: 180 degrees
4. Loosen: 180 degrees (again)
5. Torque: 31 ft-lbs.
6. Tighten: 80-90 degrees
7. Tighten: 40-45 degrees
8. Bolts 1-2 – Tighten: 40-45 degrees

I get dizzy just looking at that torque sequence. Working at the Subaru dealership must require you to have a tool like the ½” ACDelco ARM303-4A digital angle torque wrench.

ACDelco ARM303-4A Digital Angle Torque Wrench

As the name implies, this torque wrench is not only digital, but it also measures angles for the TTY fasteners we’ve just discussed above. The digital display has a backlight to make reading critical information much easier. The main body has a chrome finish to make cleanup a breeze, and the ratchet head includes a quick release button for simple and fast socket changes. The handle body is made of high-impact plastic and a rubber non-slip grip.

Setting Modes

The ACDelco ARM303-4A has three (3) modes: Trace mode (F), Peak mode (K) or Angle mode (A). Trace (F) and Peak (K) are much the same as the number on the readout increases as more force is applied. The difference being when the user releases pressure on the wrench: Trace (F) will display the preset torque that was input, while Peak (K) will display the highest number (amount of force) that was applied. Angle mode (A) will not only display the angle (rotation degrees) but also the amount of torque applied with the wrench. Selecting between these modes can be done by pressing the button with “A”, “F”, and “K”.

Unit of Measurement and Memory

The technician can choose the unit of measurement to be in inch-pounds (lb-in), foot-pounds, newton-meters (N-m), or kilogram-centimeters (Kg-cm). Pressing the “U/S” button will toggle between the different units. Thirty (30) different Memory settings can be saved for redundant jobs. Pressing the “M” button followed by the up or down arrow button will allow you to toggle between different memorized settings.

Manual Measurement Entry

Entering a new measurement is as easy as choosing the mode (“A”, “F”,  “K” button), choosing the unit of measurement (“U/S” button), then using the up or down arrow to set the value you desire. Holding down the up or down arrow button will rapidly increase or decrease the value, while pressing the up or down quickly will increase/decrease the value by one digit.

LED, Buzzer and Vibration

The LED (lights), buzzer and vibration are features you won’t find on a typical torque wrench. When the force applied reaches 80% of the desired torque, the green LED will begin to flash and an audible beep will sound, as the force reaches closer to 100%, the beeps get faster and the green LED blinks faster. Once 100% of the preset value is reached, the green LED will be solid, the beep will be constant, and the handle will vibrate. As soon the force reaches 101%, the red LED will display as well.

Specifications

• 720 degree maximum angle measure.
• Torque range: 12.5 – 250.7 ft-lbs
• LCD Backlight display.
• 2 LEDs red / green for visual alerting.
• 30 data sets of memory capacity.
• 72 Gear teeth.
• Standard functions: torque setting, measurement setting, mode setting.
• Operation in both clockwise and counter-clockwise directions.
• LCD display shows kg-cm, N-m, in-lb, ft-lb measurements.
• Audible torque confirmation by means of buzzer.
• Easy to set up Peak or Trace modes.
• Anti-slip soft grip.

Final Thoughts

I don’t know what it is, but I love working with a torque wrench. I think it’s because you know you’re at a point where things are coming together, and you know you’re doing something really important. These are critical steps in critical components that could make or break the success of your venture. Even more so, if this is your livelihood, it could mean your job or a customer is at stake.

You know that feeling you got when you used a brushless impact or drill for the first time, or when you rode a motorcycle for the first time? It’s not that you didn’t like using a brushed cordless drill, or riding your BMX bike. It was just a feeling that the other was so much better, and it was even cool. That’s kind of like I felt when I used the ½” ACDelco ARM303-4A digital angle torque wrench. The manual is a little tough to read and an obvious translation, but the tool is pretty self-explanatory to figure out.

I see two big differentiating features in the ½” ACDelco ARM303-4A digital angle torque wrench vs. the old style. One, the technician has the ability to set and measure angles for TTY fasteners. Second, you can see, hear, and feel the incrementing force being applied to the fastener as you pull the torque wrench.

Hidden Value

Building more horsepower is a game of fractions of inches. Sure, go-fast parts are an important part of the build, but it’s not everything. If you can’t keep that rotating assembly and combustion area together, then all you’ll have is a well ventilated air pump. Maximizing the clamping force of rod bolts, main caps, and head bolts are critical to making more power. Therefore, you need a torque wrench that can provide the measuring capabilities that will make you successful, every time.

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The ½” ACDelco ARM303-4A digital angle torque wrench is a great choice to upgrade your old torque wrench, and you can purchase it here.