WHEN it comes to radial racing, No Mercy is the be-all and end-all. It is the Superbowl for American radial racers, and our man on the ground in the US, Luke Nieuwhof, was there to capture all the action. Check out the video coverage from the event, as well a rundown of the different classes below.
Radial vs The World
The big boys of radial racing, with massive prizemoney on offer and virtually no rules. Any chassis is permitted including Pro Mod style cars, along with wheelies bars and any transmission you like.
The only proviso is that dual power adders (for example, nitrous and a turbo) are not permitted, though you can run twin turbos. There are also different minimum weights for different power adders, with small-block naturally aspirated motors having no minimum weight, while a twin-turbo big-block (106 turbos and bigger) must weigh over 3000 pounds.
Limited to a Mickey Thompson Pro 275 radial tyre, Pro 275 cars can use any engine and transmission combination but are limited in chassis specs.
No Pro Mod style cars are allowed and no wheelie bars are permitted. Stock wheelbase and stock appearing bodies must be maintained, but rear suspension can be modified to any extent.
Like Radial vs The World, there are extensive weight breaks to maintain parity. Small-block naturally aspirated cars have a minimum of 2100 pounds while big-block screw-supercharged cars need to come in at 3150 pounds.
Many Australian drag racing fans will be familiar with X275, which is frequently run in Oz. The rules are more extensive than Pro 275.
Power adder cars require a 275/60/15 drag radial tyre, though naturally aspirated cars are permitted to use a 28×10.5in slick.
There are rules to keep the cars more street appearing, including a full interior and functional lights, and chassis modifications are very limited.
From here we go down the rabbit hole of rules for different engine combinations, with various weight penalties. For instance, a lock-up convertor on any combination will cost you 50 pounds, while a single 4150 carb/throttle body on a small-block with nitrous or naturally aspirated will allow you to take 50 pounds off. The ruleset is surprisingly complex in an effort to keep this heads-up racing close.
Limited Drag Radial
Not quite so onerous is Limited Drag Radial. Any 275/60/15 drag radial is permitted, while the Mickey Thompson 295/65/15 Drag Radial and Mickey Thompson 29in Pro Drag Radial are the two legal tyres for a ‘big’ tyre option – though any 481X/Hemi/Hemispherical Headed BBC or BBF equipped with single or twin turbochargers or a centrifugal supercharger must be on a 275/60/15 drag radial, with no big tyre option.
Backhalf style cars are permitted, but factory body lines must remain.
Screw superchargers are prohibited in this class.
Very similar to X275 but way more limited in the power adder department. For instance, only single turbochargers are permitted and they must be manufactured from factory – no hybrids allowed.
Interestingly, pre-1978 vehicles get a 50-pound weight break.
A heads-up class designed for passenger cars and trucks from a major manufacturer, weighing a minimum of 2850 pounds. Powered by small-blocks only with a maximum cubic inch limit of 470 cubic inches. Only one 10- or 15-pound nitrous bottle is permitted.
As the name would suggest, very street appearing vehicles with a focus on the ET Street style radials, the idea being you could practically drive the car to the track on the tyres it races with.
A matrix of power adder and engine combinations provides a complicated set of minimum weights, with penalties for some tyre types.
If you like nitrous this is your class, as turbochargers and superchargers are prohibited. The body and chassis rules are more liberal, but the weight limits are up there – 3000 pounds if you are at the 632-640ci engine level. Seems like a good place to get your feet wet in heads-up nitrous racing before moving on to something like Radial vs The World.