Unlike a flexible belt or chain, this gear drive assembly mounts solidly to a 3/8" thick steel plate which is bolted securely to the block, so the timing can't vary on its own. Once the assembly has been installed, adjustments to the timing are simply achieved by changing the position of the cam gear on the cam hub. Each movement is detailed on the provided chart which gives the exact position for the desired amount of advance or retard, once top dead center has been found. Made in America, it is designed and manufactured to be superior in quality, strength, and durability. This under cover model fits under the stock front cover with very slight fitting.