Overclocking Older Systems

It seems like I have thousands of 486 junker computers. These computers are great for small tasks that do not require high speeds. Although it may seem pointless, I’m over clocking one of them. It is an AMD 486DX-4 100 Enhanced running at 120 (Benchmarked at P75) I was wondering if anyone had any info on how far I could go with this processor in Mhz and Voltage before I end up frying the chip completely. The motherboard is a MB-8433UUD Ver 3.1 with 16 meg ram and various other optional equipment. If anyone has any ideas please respond. Thanks