An incredible value, the NRHS Stage 1 Big Twin heads deliver a big improvement in torque and horsepower without taking a big bite out of your wallet! The key is NRHS's attention to detail. We start with a thorough cleaning and inspection of the castings, looking for cracks or other flaws that could compromise the head. All valves are then inspected for straightness and then re-faced. The intake and exhaust ports are then reshaped using a state-of-the-art CNC machine to optimize torque and horsepower producing airspeed, removing only the absolutely necessary amount of material. The valve job consists of a proprietary profile specific to NRHS. The head surface area is then flat-milled to ensure an absolutely flat gasket surface and to correct for the small amount of material removed during the blending process. The heads are then re-cleaned and assembled with all valve spring installed heights within .005 in. of one another to reduce valve train harmonics to a minimum. Finally, the heads go back on the flow bench one last time to ensure balanced, correct flow for maximum power and ease of tuning. The result to you is more horsepower and arm-yanking torque, without costing an arm and a leg!

Stage 2 light now available-  $750!!!

NRHS is proud to announce our newest stage of headwork for Evo Big Twin heads.  We call it stage 2 light.  You still get the same great CNC porting that our regular stage 2 kits come with plus stainless  7mm valves with a black diamond coating in 1.900 Intake and 1.630 exhaust sizes, beehive springs and bronze guides and seals.  We have found that when using cams with lifts of .550 or less that the new beehive spring kits from HD work excellent.  By using these springs you not only save money but also eliminate the need for rocker box clearancing and put less strain on the valvetrain components.  The perfect choice for cams such as S&S 510, Andrews EV 27 and SE 511s.  It is recommended that you use adjustable pushrods with these heads. The best part is the cost.  Only $750 using your heads!!!

Looking to build a real hot-rod? The NRHS Stage 2 Big Twin CNC ported heads are for you! Every head is CNC ported on state-of-the-art equipment and then flow tested to guarantee the quality and performance. These work very well in heavy or light bikes, whether they're carbureted or fuel injected, because the port and chamber are designed to produce outstanding torque and horsepower across a broad rpm range. With Stage 2, you get all of the same meticulous attention that Stage 1 heads receive, plus you get premium components such as the chromium silicon valve springs accommodating cam lifts up to .600" and oversize 1.850"/1.615" NRHS Hurricane valves machined to a proprietary profile to maximize flow over the entire lift range. This valve along with NRHS's own valve seat profile make the head perform fantastically for many thousands of miles. If you're looking for big torque and horsepower, you can't go wrong with Stage 2 heads from NRHS!

Stage 3 heads are for the guy building a top-shelf motor, who wants the cylinder heads specifically configured for his combination and application. Each head receives NRHS's proprietary CNC-FLEX treatment, which combines the quality advantages of CNC porting with the custom configuration ability previously only possible with hand ported heads. From the quality NRHS Hurricane components to this advanced porting technique, this head is the total package. Whether you ride your bike on the street or at the track, or maybe a little of both, we feel that this is simply the best and most versatile OEM casting high performance cylinder head on the market. Like the Stage 2, these heads come ready to bolt on with NRHS Hurricane valve springs and components, plus they offer new bronze manganese valve guides of our own design, valve diameters specific to your combination, and custom cutting of the deck and/or angled squish bands to meet your needs, all at no extra cost. Stage 3 is truly a custom head designed just for your project. The results you can get from this approach will astound and amaze you!