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

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.