Finally ... a Performance Valve Spring KIT designed esp for the MINI!! Race your MINI? Are you sliding out of the turns and hovering at 8000 rpm? or At the end of the Quarter Mile is you engine twisting the High side of 8000 revs? Crower Cams and Nitrostick have come together and designed a Performance "Conical" Valve spring to allow the top end of the engine to stay "together" after pushing it to the limits. Using the "Conical" style spring allows the the top of the spring to be smaller, this allows the use of a smaller retainer and removes a lot of inertia weight. Then when matched to the New Custom Titanium retainers, not only will it sustain the 8500 revs, it is easier on the valve train. The Nitrostick Performance Valve spring KIT is drop in ready!! A Single spring with no need to mess with locater's and having to shim to gain correct installed Height and pressures. The Titanium Retainer will accept all the multi ring keepers (OEM Type) as well as most single ring, used on custom Valves. We actually called a few People that use the dual spring/spacer type set up, and asked about the Rev limitations.... one actually said that if you run our Dual spring package at those revs......" you void any warranty's" !! Yikes!! This was the reason for me to push for the specific design spring and retainers. These ARE the Spring Kit that will be on all the TPR-3 Racing Head and optional on the TPR-2's!! SOOOoo...... maybe , it is now time to upgrade?? Thanks MA Thumper