Been running these for about a thousand miles now and so far they’re great. Can definitely hear the difference in the valvetrain. Only recommendation is that they should have a disclaimer in the description that you need the upgraded crankshaft timing gear to run these springs. The stock gear can’t handle the extra spring pressure these springs provide and it will break and cause catastrophic failure (like mine did) Otherwise amazing product!

Fast shipping, everything looks good, have not installed just yet.

ive heard rumors of 9-12hp horsepower when using dual type springs on the valve train. not sure if this true or not, but i do know these beauties PERFORM. i used these on a f22c/f20head engine build. i set the valve lash to a nice middle setting and ended up setting them on the tight end after my break in oil change as you can really hear them tapping much harder and stronger. Add to that the Titanium Valve Seats and you will have a more bullet proof head not having to worry bout the seats being ground down from high revs. only problem is the price nearly doubled when i made the mistake of letting the dealer install them for me... these are definitely worth the price especially if u can Install them yourself!!