🔄 nr GUIDE 🔄
High Performance Racing Cams from NR Racing
NR stands for No Rules. When you need more performance control, consider a cam from NR Racing.
General Recommendations
Note: Cam performance varies with motors, tracks, and drivers. Our recommendations are a starting point—you may find a different grind performs better for your specific setup.
Backyard Karting
- 280-0611 - Great all-around performance
Oval Track Racing
- 252-0207 - Very small tracks, maximum 6000 RPM
- 274-0207 - On/off the gas to 7500 RPM
- 274-0607 - Breathing in corners to flat foot high bank, 8500 RPM
- 307-0807 - Maximum all-out power, flat footed low bank
Road Racing
Mini Bikes
Drag Racing
Mud Motors
- 230-0211 Marine - Mild applications
- 252-0211 Marine - Big carbs
Snowmobiles
- 280-0611 - Most applications, including racing
- 292 Series - Grass drags
Understanding Cam Specifications
Four key numbers define camshaft performance:
- ICL (Intake Centerline) - Controls where peak torque occurs (98-116°)
- LS (Lobe Separation) - Determines overlap and power band width (100-115°)
- Duration - How long valves stay open
- Lift - How far valves open (optimal around .350" at valve)
Lift
Honda heads don't respond much beyond .350" lift at the valve. A .275 lift cam with 1.3 ratio rockers achieves this. Unless the head is radically modified, gains past .350" are minimal.
Duration
Duration determines how long valves stay open. Hondas respond well to increased duration, but there are tradeoffs:
- 210-220° - High torque, great for frequent starts/stops, low RPM stalls, wide operating range. Peaks at 4500-5500 RPM, pulls to 6500 RPM
- 230-240° - Mid-range performance
- 250-260° - High RPM motors (7000+) that rarely drop below 5000 RPM
Important: Higher duration increases peak RPM but reduces idle quality and low-end torque. Smaller carbs benefit more from increased duration—a 240° to 260° upgrade shows 10% HP gain with a 28mm Mikuni but 20% with a stock carb.
ICL (Intake Centerline)
ICL determines where peak torque occurs. Most cams range from 102-110° (Honda GX160s are ~105°, GX200s are ~110° stock).
- 102° ICL - Power peaks 1000-2000 RPM lower, more low-end torque, pulls harder off corners. Ideal for tight tracks, boats, winch boarding, rock crawling
- 110° ICL - Higher RPM power band
- 114° ICL - Peaks around 9000 RPM. Perfect for large tracks (1/2 mile+) where RPM stays above 7500, but requires high-stall clutch (5000+ RPM)
LS (Lobe Separation)
LS controls overlap and affects power band width. Most cams are 106-110°.
- Narrow LS (106-107°) - More HP but smaller power band. Required for high compression (11:1+) to prevent detonation
- Wide LS - Broader power band, better for varied RPM ranges (road courses)
Lower LS = more HP but narrower band. Wider LS = more dynamic compression capability.
Application Matters
Dyno results don't always translate to track performance. Cam selection depends on your specific use:
- Mini bike vs. kart
- Dirt track vs. paved track
- Oval vs. road course
- Track size and RPM range
NR Racing Cam Numbering System
Our part numbers tell you everything about the cam:
Example: 252-0207
- First 3 digits (252) = .252" lift
- 4th & 5th digits (02) = 102° intake centerline (add 100)
- 6th & 7th digits (07) = 107° lobe separation (add 100)
- Letter "P" = Old style Predator
Example: 274-0611
- .274" lift
- 106° intake centerline
- 111° lobe separation
Note: Lobe separation = (ICL + ECL) ÷ 2
Exhaust centerline formula: ECL = (2 × LS) - ICL
Installation Notes
Small Block Engines
Compatible Engines: GX200, 6.5 Clones, Hemi Predators use the same cam
Cam Requirements:
- 274 & 307 cams: 1.2 rockers + dual springs
- 252 & 280 cams: 1.2 rockers + single springs
Important Clearancing Info:
- Old style (non-hemi) Predators: Require cam with .009" larger journal
- GX200 Honda blocks: Must be clearanced for 274+ cams
- 6.5 clone blocks: Usually clear most cams, but check due to manufacturing variances
- Hemi Predators: May have rod-to-cam interference on all non-stock cams
- 224 Predators: Can use GX200/212 Hemi cams but require clearancing along shaft and lobes
Big Block Engines
Compatible Engines: GX270, GX390, 420, and 460 all use the same cam
Note: Some 301 motors use a large journal cam
Cam Grinds - Small Blocks
230 Series: Special Cam for Classes with Lift-Only Rules
Approximately .230" lift with 30° more duration than stock. Significant power increase while maintaining factory lift. Bolt-in installation, no block modifications required. Maintains stock base circle for correct valve train geometry. Works best with 22lb springs (6500 RPM). Can use 26lb springs for higher RPM but may experience cam wear. Note: Cam may have noticeable idle and will not pass visual inspection.
230-0211 Marine: High-torque cam for marine applications. Great for road racing and mini bikes. 5500 RPM, 10:1 compression or lower.
230-0611: All-around grind for medium to large road racing tracks. Wide powerband. Works great on mini bikes needing high RPM power with some low end. 6500+ RPM, 10:1 compression recommended.
252 Series: Approximately .252" Lift and 230° Duration (at .050)
Welded and ground cam with significant power improvements over stock. Works best with mild motors using bored OEM or aftermarket carbs. Bolt-in installation, no block modifications required. Maintains stock base circle for correct valve train geometry. Use 26-37lb springs. Great with 1.3 rockers. OUR #1 SELLER!
252-0207: Special high-torque grind for small tracks. 6000 RPM. 22lb springs required, 26lb recommended. 10:1 or higher compression recommended (works with lower ratios). Best choice for low-end power, especially small dirt oval tracks with heavy drivers.
252-0211: Same as 0207 but for road race, wide powerband applications (GX200, 6.5 Chinese OHVs, Predators only). 7000 RPM, 26lb springs required. 10:1 compression or lower. Great for marine and winch applications.
252-0607: Oval track grind, high-RPM applications. 7500 RPM maximum (GX200, 6.5 Chinese OHVs, Predators only).
252-0611: Same as 0607 for road race, wide powerband applications (GX200, 6.5 Chinese OHVs, Predators only). Also recommended for mini bikes!
Rattlesnake 252: Non-welded economy grind, same specs as 252-0611, but for 22lb springs.
252-1007 (GX120 only): High RPM grind for large tracks. 8500+ RPM, 26lb springs required. 11:1 compression or higher.
Note: Marine and winch board applications work best with 252-0211. Mini bikes work best with 252-0611.
272 Mongoose Performance Camshaft
Approximately .272" lift and 245° duration (at .050). Ground and hardened (non-welded) high-performance cam designed for wide powerband with awesome mid-range power increases. Works best with bored OEM or aftermarket carbs. 26lb springs recommended. 6500-7500 RPM based on springs and carb.
274 (F200) Series: Radical Cam Grind for F200 Series and Super Box Stock
Approximately .274" lift and 260° duration. Square lobe design maximizes valve opening time. While meant for larger carbs, works very well with smaller carbs by holding valve open as long as possible with reduced lift to maximize velocity. Honda blocks may need clearancing. Dual springs recommended (37lb will work but limits RPM to 7500).
274-0207: Super high torque for small to medium tracks. 4500-7500 RPM range, 11:1 or higher compression required. Designed to get you off the corners. OUR #1 SELLER!
274-0211: Same as 0207 but with wider torque curve. Works best with 10.5:1 or less compression. Great for road racing and marine applications.
274-0607: 8500 RPM, 12:1 or higher compression required. Big track cam! Warning: may cause traction problems. Use with 1.2 billet steel rockers for maximum power.
274-1007: 9000+ RPM, 12:1 or higher compression required. Recommended for serious competition! Use for large ovals or where traction is a problem. Dual springs required.
280 Series: The Original NR Camshaft - King of Mid-range
Approximately .280" lift and 220° duration (at .050). Works well on both stock and modified motors. Produces lots of low-end torque. One of the best all-around cams we offer. Honda blocks may need clearancing. 26lb springs required. Bored or aftermarket carb needed. Great for mini bikes & marine applications!
280-0611: Good torque cam with excellent power. 7500 RPM. 10.5:1 compression or more. 26+ lb springs.
280-0211: The ultimate torque cam. Special grind for marine and winch boarding applications. Extreme torque. Designed for 2000-5500 RPM, 11:1 or lower compression required. HD springs required.
285 Series: Serious Mid-range Camshaft for Serious Motors
Approximately .285" lift and 250° duration (at .050). Lobe specially designed for Honda GX series. Allows use of stock valves with 1.2 rocker arms when using our springs. Likes big carbs and big ports. Will easily make 20hp with correct combination. Works best with 24mm Mikunis, big valves, and high compression. Honda blocks must be clearanced.
285-0211: 7000 RPM. 11:1 compression or more. 26+ lb springs required. Small track cam for serious torque.
285-0611: 8000 RPM. 11:1 compression or more. Dual springs required. Recommended for most serious GX200s needing good mid-range torque.
292 Series: Radical Cam Grind for Drag Racing
Approximately .292" lift and 260° duration. Square lobe design maximizes valve opening time. 108° ICL, 110° LS. Works well in most high-RPM applications but designed for wide RPM range to maximize acceleration. Pulls hard from 4000-9000 RPM. Honda blocks may need clearancing. Dual springs recommended (37lb will work but limits RPM to 7500).
307 Series: All-out Racing Camshaft for Serious Motors and Big Tracks
Approximately .307" lift and 260° duration. Took 6 months to develop. Special ramp designed for Honda GX200s running 12:1 or higher compression using race gas or methanol. Use with dual springs and 1.2 rockers. This is the cam for 20+ HP motors. 9000 RPM. 12:1 compression or more. 108° ICL, 107° LS.
Note: Use of rockers longer than 1.2 with dual springs may result in retainer to guide interference. Block or crankshaft may require clearancing to clear camshaft lobes.
320 Series: The Biggest, Baddest Cam for GX200s!
Approximately .320" lift and 260° duration. Requires dual springs and special attention to valve train. Block and rod must be clearanced to install.
320-1007: 8500+ RPM. The hottest cam available for GX160/200s. Big valve and big carbs required. Dual springs required. Heads will need spring pocket cut. 12:1 or higher compression required. 20+ HP. .320" lift, 110° ICL, 107° LS.
Note: Block or crankshaft may require clearancing to clear camshaft lobes.