In the past, engines came from the factory with keyways cut into both the crankshaft and damper hub, and we’re held together with a square key. However, when the LS1 was released, it came with a smooth crankshaft snout and the damper was simply press-fit onto the hub, and that was enough interference to prevent the damper from rotating on the crankshaft. The phrase “pinning your crank” hadn’t entered the automotive lexicon yet.
However, the LS1 became a hit with the performance aftermarket and in short order it was realized that not having mechanical retention was an issue. “The ASA Racing Series went to sealed, LS1 Engines for the 2000 racing season. Lingenfelter built all the engines using an ATI Super Damper. Of course the engine came with no keyway and relied on the friction washer only,” explains ATI Performance Products’ J.C. Beattie, Jr.
“The ASA series ran some one-day events, where you would have to qualify and then race with the same set-up. This meant on brand-new tires, set up for a long race, the car would bounce off the rev limiter a number of times at the end of each straight. Then again in the race after each tire change and we soon discovered this was causing the snout to recoil backwards on each hit and ultimately allow the damper to spin on the snout and loosen the crank bolt. Since all of the engines were built already, Jim Beattie came up with the patented ATI Damper Crank Pin Drill Fixture that we still offer today.”
Here you can see the contents of the kit. The two drill guides are held in the fixture byt the large screw and the long drill bit allows access from a variety of positions, whether the engine is on a stand or in the car. The reamer ensures that the hole is perfectly sized.
Why Pin The Crank?
If you have the engine apart, you can add single and even double keyways for today’s most aggressive use-cases. However, probably ninety percent of the people who can benefit from a keyed crank will never have the engine out of the car, let alone the crankshaft out of the block. So ATI’s drilling fixture allows you to mechanically secure the damper hub to the crankshaft, while everything is still in the car.
“The [factory] press fit, combined with the clamping load from the crank bolt, do a good job of holding the damper from spinning in normal circumstances, but most of us are not interested in ‘normal’,” laughs ATI’s Stuart Smith. “If you are planning on aggressive driving, track days, nitrous, or a supercharger then using the ATI pin kit is a great idea before you install your new ATI damper.” In addition to the pin Smith absolutely recommends upgrading to an aftermarket, ARP specifically, crank bolt for its proven durability under stress.
Another scenario that is often overlooked, which Smith touched on in his previous comment, is the use of the crank pin in naturally aspirated applications. We are guilty of associating the need for a key or crank pin only with supercharged applications, and he points out that’s a very narrow point of view. “Aggressive street driving, track days, HPDE clinics, and autocross are all situations that can allow the load on the damper to strain the ability for the hub to grip the crank snout in a naturally aspirated application,” says Smith.
“Consider the load on your damper at 7,000 rpm with your full array of electronics, water pump, and even A/C all pulling hard while you paddle shift your way around a parking lot in an autocross event. Your gear changes are lightning fast, upshifting and downshifting your accessory drive (and its load) hundreds [if not thousands] of RPM in a split second.”
This is what the kit looks like set up and ready to drill. The kit is retained by the old crank bolt. ATI recommends the use of a new, high-quality bolt when you reinstall your damper — specifically ARP.
No Machine Shop Needed
While having your crankshaft and hub machined for a key requires a trip to the local machine shop, pinning your crankshaft, on the other hand, is a completely DIY process. “The kit was developed for the DIY guy since the race teams all needed to do it in the ASA series,” Beattie explains. “The kit comes with drill bushings, and a long drill and ream so the customer has room to clock a drill somewhere under the hood or from under the car and drill and then ream the correct size hole for the hardened pin. You can even add a second pin if you have higher boost and want dual keyways.”
If you were raised to be wary of things that sound too good to be true, Your skepticism is appreciated. We asked if there were any drawbacks compared to a standard key. Surprisingly, Beattie responded in the affirmative. “Yes it is a tradeoff, crank pinning is simpler, in that it can be done with the motor in the car or after it is built, therefore you don’t have to remove the motor or the crank which saves time and money. If you are starting from scratch then you absolutely want a keyway or two in the snout if you are doing a large supercharger combo.”
So, ultimately it comes down to cost and convenience for most people. Crank pinning has proven itself to be a beneficial piece of engineering that is surprisingly simple to handle in your garage. It’s been so successful, that even though it started with the LS-series engines, as more OEMs have moved to press-fit-only balancers, ATI has developed more and more crank pinning kits. And, for those of you who prefer a key, all of ATI’s hubs come pre-machined for a standard key, and can be double-keyed on request. The pins in the crank pin kit are designed to fit the standard 3/16-inch keyway that comes standard from ATI.
So the answers we came looking for are that not only can a supercharged application take advantage of having the crank-snout pinned to mechanically prevent the damper hub from rotating, but that there exists several quite-common naturally-aspirated use cases that would benefit from a crank pinning as well. Now, we’re going to go check our recently acquired LS1 and see if the previous owner pinned the crank.
The final product. The pin is left .093 inch proud to perfectly fit the keyways that come standard on all of ATI’s damper hubs — even applications that don’t have keyways from the factory.
