ManjotMANN :
Hi im planning to build a pc with corsair vengence lpx 2x8gb and wanted to ask if i can use corsiar vengence lpx 2x4gb with it with no problems
If you need more then buy more in a matched set as in one package.
For your question their no 100% answer. Should work, might work, might not work, might be made to work with some tweaking.
I have 32GB in mine I have never used that much but was running out with 16GB using some programs and the most I have used of the 32GB is in the 25GB area.