I always use them and I've had good results. Some have a different break in procedure so read the instructions specific for your set. The gapless cuts down on blowby and in certain cir***stances this is helpful. Blowby is not a problem on properly built mild and normally aspirated SBC street engine but if your building something exotic they can help attain a better seal. For example...I built a twin turbo motor that was running 24lbs of boost. At that level of boosts you have to run a forged piston loose and that can create excessive blowby so the gapless helps keep the seal as the piston rocks. Same effect with a piston setup for NOS . Since they seal better you get a bit more dynamic compression too.
The Jalopy Journal
