Are Ultra4 4400's The Best Built Race Trucks On The Planet? | KOH

King of The Hammers and Ultra4 4400 racing with Dobry Designs

Sam of Dobry Designs runs us through this Genright Racing Team 600hp LS7 powered Ultra4 buggy built for one of the toughest offroad racing events on the planet, King of the Hammers. KOH sees vehicles race at opposite ends of the offroading world at the same time seeing speeds over 100mph across open desert into rock sections that see vehicles doing single-digit speeds, or sometimes even less as they hit reverse to try another line or drive around (sometimes even over) a struggling competitor.

Ultra KotH in car

In this interview via the SEMA Torco Racing Oils & Fuels stand Conner & Sam discuss:
- What is KOH?
- Cooling setup
- Design fundamentals including 'Rod Ends In Bending' explanation (REIB)
- Oil pressures vs parts reliability and longevity & damaging oil vapour
- Full independent suspension vs solid axle for KOH
- Drag radials as 40" offroad tyres
- Massive ground clearance without the height/COG (center of gravity) issues
- Tyre construction & weight gives huge advantages for mixed terrain & speeds

Ultra KotH rose joint close up

600hp LS7 based engine with RHS tall deck, All Pro heads, COMP cams & Johnsons high performance driven dry sump system.
Custom Griffin radiator, oil cooler only for summer racing.
Turbo 400 transmission, spool rear one way locker front using Tubeworks 9.5" fork style differential & Atlas transfer case.
4-wheel independent suspension, double wishbone with a 5-link rear.
Portal axles allow 3:1 diff ratio for high-speed section advantage and less CV breakages
40" Mickey Thompson Baja Boss tyres on 17" rims.

For more KOH & offroad racing content check out: @jordanpellegrino @genrightoffroad @jamipellegrino @michkeythompsontires

Ultra KotH rear suspension

Ultra4 Unlimted Class Explanation
"4400: ULTRA4 Unlimited Class This is the original unlimited class that started the King of The Hammers. These cars are not limited on tire size, engine or chassis design, other than to meet the safety requirements for the class. Unlimited cars must have a transfer case and be able to be driven in 4WD. These cars can be straight axle, or independent front suspension (IFS)" -
0:00 - Dobry Designs
0:20 - What Is King Of The Hammers?
1:22 - LS7 Based Engine
202 - Heat Management
2:30 - Cooling Removed for KoH
2:59 - Dry Sump System
3:46 - Oil Pressure 101
4:56 - Drivetrain
5:36 - Why Independent Suspension Over Solid Axle?
7:46 - Double Wishbone
8:48 - Height and COG
10:12 - Multi-link Rear
10:50 - Rod Ends
11:42 - 'Rod Ends In Bending' - Explanation
12:45 - Fatigue A Large Design Consideration
13:03 - 40" Mickey Thompson's
14:43 - Free Lessons

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