Does the quality of valves make much difference. In some cases, I see a full set of intake and exhustvalve set (for ecotec 2.4L) for just under $100 while other valves are $40 each.
As long as the piston doesn't hit the valves, I would think either would be Ok?

Personally, I go by the bigger picture. For example: Over at Rock Auto, they have three manufacturers of valves for your car; SBI, Melling, and GM Genuine. For intake valves, GM Genuine is the most expensive, followed by SBI and Melling. For exhaust valves, SBI is the most expensive, followed by Melling then GM Genuine.

I've never heard of SBI. Maybe they're good, maybe not. I just don't know, so I mark them off my list because there are good alternatives. Intake and exhaust valves aren't somewhere that'* advisable to scrimp. If they fail you likely lose an engine. Melling has a good reputation, and GM Genuine does as well. I tend to lean toward GM Genuine on these kind of parts, because theoretically they are stamped out the way they do for the factory so if they aren't stupid expensive then I'll go that route. If GM Genuine is stupid expensive I'd go with Melling.

At Rock Auto, at this moment:

Intake:
$22.79 GM Genuine <<< This feels like "stupid expensive" in this list, but I'll see where the totals end up
$5.41 Melling
$8.66 SBI

Exhaust:
$7.93 GM Genuine
$8.15 Melling
$9.28 SBI

Totals:
$182.32 if I do all GM Genuine (Now those "stupid-expensive feeling" intake valves don't feel so bad.)
$108.48 if I do all Melling (Is it worth $73.84 to me to have to lose the engine or tear it apart again to fix something? No.)
$143.52 if I do all SBI (I already don't know anything about this manufacturer, is it worth $38.80 to me to have to lose the engine or tear it apart again to fix something? No.)
$106.72 if I do Melling intake and GM Genuine exhaust (Is it worth $75.60 to me to have to lose the engine or tear it apart again to fix something? No.)

Of course, another consideration is how long you intend to keep the car . . . but that cuts both ways as well:
- I'm keeping it forever, I want quality parts so I never have to dig into it again!
- I'm getting rid of it, so I don't want to invest any more time and treasure into it than I have to, so I don't want to lose an engine or spend time and treasure tearing it apart again!

For me, the totals make the decision for me. There isn't enough of a difference between GM Genuine prices and everything else to justify saving a few bucks at the risk of increasing my odds of problems.

My $0.02 .

I have valves that are Ok. Can I just clean them off and replaced the damaged ones with different brand or would small differences in weight etc. cause vibrations.
Anyone use valves from different brands?

What damage do they have?

I wouldn't.

It is too inexpensive to replace them all for me to fiddle with skimping on something like that. No way I'd want to get that far into an overhead-cam engine, or any engine for that matter, skimp on something like that so I can save a few bucks, put it all back together, then hope it works right then and also hope it works for tens of thousands of miles. If we were talking a like grand or more, then I might change my tune a little.

I have one vehicle that has a used exhaust valve from a different engine than all of the rest, and it came from the same build-code engine as mine. This valve replaced a burned valve in an otherwise perfect engine. This was because it has special sodium-filled exhaust valves that most of them didn't have, and the work was being done in 1997 when everybody and their grandmother weren't manufacturing sodium-filled valves yet. The work was done by a machine shop that knew what they were doing and had access to all of the necessary tools.

Besides, all of the valves in your engine have been through similar life experiences as the valves you are looking to replace.

As far as vibrations go, I don't think you'd feel anything from this if all the valves are sealing properly and the engine is running properly.

Which valves get the most "beating" over time..intake or exhaust. If someone uses 2 brands, you would want the better on the side that gets more beating?

With direct injection and on some SFI fuel systems the intake valves get carbon buildup on the back of the valve. Exhaust valves take the heat and they will burn easier than the intake valves.

Thanks..I don't understand the term "burn" . They are metal...Are you saying that they heat up more and thus their shape changes due to heat and then they won't seal as well?

The metal will burn right off the valve edge and face. I've seen some that a third or more of the valve was missing due to metal burn.

Wow!! I assume this only happens on an engine that has overheated and never under normal running temperatures.

I've seen it on many that never over heated. The exhaust valves take a beating with heat. If carbon gets adhered to them and in the right conditions it can burn like an acetylene torch and melt off a significant amount of the valve. I've seen carbon destroy pistons, rings and valves in perfectly normal operating engines.