Inertia Ring; Increase your low-end grunt

by Norm Wnuk

Finding that your four popper that poops out below a thousand RPM, a six that get sick at eight hundred RPM or and eight that has high RPM gusto and bogs on the bottom? An Inertia Ring may be what your need.

What is an Inertia Ring? Balanced weight you add to your flywheel. By increasing the weight of your flywheel you create energy stored in the form of inertia and give your motor more torque (in the form of stored energy) and less chance of stalling at low RPMs.

How Do I make an Inertia Ring? This is a good project if you are changing your clutch or doing tranny work. You need to remove your flywheel (this is for standard transmissions only) and create a heavy ring, which you bolt to it. After careful measuring, I cut a ring from ½ steel plate that fit on the inside of the starter ring. You can use a Plasma cutter or cutting torch and get it as close as possible to round. I used the threaded holes for the clutch plate to bolt it to the backside of the flywheel, and used two pins to locate the inertia ring so it can only be installed in the same position. Once I had this together I brought it to a balancing shop to have it dynamically balanced to the flywheel. This is important! You can also have a machine shop cut and balance the inertia ring at the same time. Static balancing won't cut it, so make sure they can spin the whole unit up when balancing it. The ring I made added ten pounds to the flywheel.

Tips for making an Inertia Ring. Make sure you check the clearance of the ring to the engine block. The heavier the ring and the farther out from the center of the flywheel, the greater the effect. Be careful mount it one way so you don't throw off balance if you take it off or reinstall it. If you don't pin it, mark it so it can be reinstalled in the same position.

What are the results? The results are phenomenal! I installed it on a Jeep inline six. I can't stall the engine now. (OK, well almost never) If I dump the clutch in first gear (high range) at and idle it chirps the tire and goes. Another thing I couldn't do before is drive from first gear to fifth gear/OD at engine idle (400-500 RPM). The engine pulls at idle with no throttle in overdrive at 20mph at about 500 RPM. I definitely couldn't do this before. [This is with 32" street tires on a very heavy Scrambler]. The only potential downside is my ¼ mile time probably went down by two-tenth of a second, good thing I don't drag race this beast. I have not noticed any difference in acceleration.