Before The Test
So it looks like it's time to jump in and have an engine dyno tested. What steps can you take ahead of time before getting there? The first step is to find the right dyno shop to do the job. It is worthwhile to make some inquiries both at potential shops and within the local performance community to get an insight into the facility. One of the key reasons for considering a dyno test is that it can provide a roadmap to making more power, if you know how to find it. This can have less to do with equipment than with personnel. An experienced and knowledgeable dyno operator will add immeasurably to the value of a test, and the operator will usually be the point man when it comes to finding that "magic tune." Experience plays a key role here-remember you are paying for the operator's time as well as for the time on the machine. A skilled operator will be an asset in evaluating the data from the dyno, and making interpretations that can lead to improved performance. Just as importantly, a skilled operator will often detect and head-off problems before they develop into serious trouble, and help find faults if they occur. Choose the shop carefully.
Preparing for a dyno test should begin with a conversation with the dyno operator. It's important that everyone is clear on what the objectives and goals of the test will be, and that everything required is identified ahead of time. Besides discussing the basic engine combination, it is important to be clear about what additional testing you'd like to accomplish. You'll need to know what components in addition to the engine assembly will be required for testing, which will vary from shop to shop. You may need to supply a set of headers, though in some cases the shop will have dedicated dyno headers, often set up to accept exhaust gas temperature probes. The dyno may be equipped with an ignition system, or you may elect to run the system that will be used in the truck. It's important to discuss the requirements and capabilities of the shop to run ancillary equipment, such as nitrous, blowers, or a dry sump. Find out what equipment and supplies the shop has on hand before showing up on test day. Things to consider include:
* Pre-lube adapter
* Carburetor
* Fuel lines, especially for multi carbs
* Headers
* Mufflers
* Motor mounts
* Bellhousing
* Starter
* Ignition system
* Fuel pump
* Spark-plug wires
* Flywheel
* Oil and filters
* Fuel
* Tuning parts (Jets, spark plugs, and so on)
* Gaskets
* Special tools
Don't hesitate to ask the dyno shop to detail just what items you will be required to bring. Nothing will ruin a dyno day like getting there and then realizing the test can't be run because something sitting in your garage needs to be with you on the day. It pays to make a checklist and get prepared before test day comes around.
Test Day: The Fire-Up
If you've gone through the prep and come to the dyno shop locked and loaded with all the gear needed-and an engine ready to run-you'll be way ahead of the game. This will save considerable time in the setup, giving more time for testing. Once the engine is mounted and the dyno connections are made, you'll soon be ready for fire-up, but not before some preliminary steps. The engine's lubrication system should be primed or prelubed, usually via a drill motor and an oil-pump drive adapter. The oil pressure should be confirmed. Ideally, the valve adjustments, if applicable, should have already been done. The engine should be static-timed, and the firing order and ignition system connections confirmed. A fuel system check should be made, ensuring the fuel pressure is set at the required level and that there are no fuel leaks. With a carburetor, check that the float level is at specifications and there is no flooding or fuel flow with the pump on and the engine off. Confirm cooling water in the engine, the dyno cooling tower, and that the dyno or engine's water pump is functional. Finally, connect a timing light to the engine, and have it standing by. All of these steps help ensure that the engine will fire immediately.
If everything is right, the ignition and fuel pumps will be switched on at the dyno control console, and the engine should fire after a few cranks of the starter. The oil pressure should be confirmed once the engine comes to life, and the dyno instruments checked for any immediate signs of problems. If the engine is new, a break-in cycle will be the first phase of testing. Some dynos have an automated cycle to vary the rpm and load for a break-in period. Back in the test cell, once the engine is fired the timing should be checked and adjusted to confirm it is in a safe range. If the dyno doesn't have an exhaust gas temperature (EGT) setup, check that all the cylinders are firing with a temperature gun reading on each cylinder's header tube. Look and listen for any problems, like fluid leaks, burning wires, or any type of scary death sounds. A mechanic's stethoscope is a good way to look for valvetrain noises or other brewing trouble. Shut down and repair or investigate if something isn't right. After the engine is idled down from the initial run-in, the carb or injection system's idle adjustments should be made.
If the engine is equipped with solid lifters, after the engine is shut-down following the initial run-in, the first step should be resetting the valve lash with the engine hot. Temperature changes the clearances, and a hot-lash setting is truer to the actual operating condition. If any of the valves have a significantly different or changed clearance at this point, diligently check that valve for any abnormality or problem.