so sorry but can some one explain the advantage or even how they work really......but going with +1mm vavles what will this really do? worth it or not?

http://www.jbodyperformance.com/new/...Cobalt/Redline

 

Some parts exist because of racing rules. This might be the case with the +1 mm valves.

For example, in stock class some rules allow a "clean-up" bore of .010. Racers build their engines to that number even from scratch to get that little, tiny extra displacement. Chrysler offered an offset-ground crankshaft with matching offset pin pistons for the Gen I Neon to gain .030 stroke due to NHRA rules that allow cranks to be ground .030. Again, it was a lot of money for such a tiny displacement increase.

The valve thing might be the same - someone might allow a 1 mm oversize valve for clean-up grinding. If so, racers will grind the seats to the limit of the rules to get that tiny extra amount of flow.

The actual gain from any one of these is very minimal, but in some classes it can make the difference between a win and a loss. Probably not worth it on the street.

Just one possible explanation.