The Moroso leak down tester can be held in one hand. It has a clean design with an easily read dial. Words and photos by Darr Hawthorne Courtesy of http://www.dragracingonline.com One of the most important tools in any serious racer’s trailer is some type of “leak down” tester. It is an invaluable piece of equipment that when used properly can tell racers what is going on in each cylinder without removing the cylinder head to check for burned or broken valves, rings and pistons. After a run the tuner uses the device to determine if a cylinder/combustion chamber still has a seal. This is done by pressurizing each combustion chamber and then measuring how good the seal is. The more air that escapes from the chamber during a given amount of time, the less efficient it will be. Traditionally, leak down testers are hand-made or purchased long ago and handed down from racer to racer, or father to son. If you wanted one of the preferred devices, they were built around 50 years ago and now are often hard to find, with eBay being the place to try and find the older, used units. The engineers at Moroso went to work to develop a brand new tester that somewhat resembles the antiques racers had to use. What they have developed for racers is a modern tester built using brand-new components that gives racers better and more reliable information. In order to find out how well the tester actually works, we decided to take one of Moroso’s new units to the races and find out firsthand. DRO approached veteran nitro tuner and crew chief Donnie Couch from the West Coast Funny Car Factory to test the Moroso unit. He agreed to test the new unit on the blown and injected Brad Anderson Engineering nitro engine in his AA/FC. After each pass or warm-up Couch checked the leak down for each cylinder using the whip air lines that come with the unit. Other components that come with the new unit includes the necessary 14mm and 18mm adapters and a tapered plug adapter to pressurize the cylinders one at a time. With the whip line in place, the plugless engine is turned over until the compression stroke is determined. An air supply input from a compressor or air tank is connected to the input plug - and the cylinder whip line is connected to the output plug. The Moroso 89603 Leak Down Tester is easily moved from side to side and can also be held by crewmembers to obtain readings. On this engine, Couch wants under 20% leakage per cylinder. With the Moroso 89603 tester, Couch can also make precise adjustments to the fuel system’s barrel valve rather than being forced to eyeball his set-up. Those precise, repeatable settings to the barrel valve mean better performance and could help in preventing engine explosions. The Moroso 89603 includes complete instruction with illustrations to measure both cylinder leak down and barrel valve adjustments and is easily set up for either. Couch, who has tuned and crewed on winning nitro racecars as varied as Billy Meyer, Dante Pastorini, Tom McEwen and Shirley Muldowney, felt the Moroso Cylinder Leak Down Tester was easily readable and provided the precise information he needed both in the shop and in the pits for his nostalgia nitro funny car engine. The unit is easily calibrated for high accuracy and ultimate repeatability. The Moroso 89603 Cylinder Leak Down Tester is available directly from Moroso Performance Products or most of the mail order catalog online stores. For more information and a downloadable instruction booklet go to www.moroso.com.