Works well with ported cylinder heads .Requires high lift springs (Gen 1) Stock springs for Gen 2150+HP possible when used in 128/131 big bore builds.10.8-11.5:1 compressionM8 APE/CR515$369.00PriceShipping InformationQuantity*Add to CartBuy NowAdditional Information Weight3 lbsDimensions8 × 6 × 6 in