Setting your max clients to 220 on that setup is a terrible idea. You will probably cause the machine to start swapping as there is insufficient memory for each PHP process. It will grind to a slow halt. You should calculate your MaxClients based on the amount of load the machine can actually handle, not the amount you wish it could handle :-)

A conservative estimate of 20MB per PHP process would already put the requirements for 220 of them at over 4GB (twice what you have) and that's not allowing anything for the OS and anything else running on the machine. Its not an exact science figuring out the appropriate MaxClients, but you should find out how much the rest of the machine needs, look up the average Apache process size (ps), divide the available memory by that and then reduce it a little. Use this as you starting point for figuring out the MaxClients. Keep an eye on the available free memory for a while (vmstat) and gradually up that limit until you reach a comfortable working level for the setting.