Straight from the rule book,
4:10 ROLL BAR
All roll bars must be within 6 inches of the rear, or side, of the
driver’s head, extend in height at least 3 inches above the driver’s
helmet with driver in normal driving position or be within 1 inch of
the roof/headliner in the area above the driver's helmet, and be at
least as wide as the driver's shoulders or within 1 inch of the
driver's door. Roll bar must be adequately supported or crossbraced
to prevent forward or lateral collapse. Rear braces must be
of the same diameter and wall thickness as the roll bar and
intersect with the roll bar at a point not more than 5 inches from the
top of the roll bar. Crossbar and rear braces must be welded to
main hoop. Sidebar must be included on driver’s side and must
pass the driver at a point midway between the shoulder and elbow.
Swing-out sidebar permitted. All roll bars must have in their
construction a cross bar for seat bracing and as the shoulder
harness attachment point; cross bar must be installed no more than
4 inches below, and not above, the driver’s shoulders or to side bar.
All vehicles with OEM frame must have roll bar welded or bolted to
frame; installation of frame connectors on unibody cars does not
constitute a frame; therefore it is not necessary to have the roll bar
attached to the frame. Unibody cars with stock floor and firewall
(wheeltubs permitted) may attach roll bar with 6-inch x 6-inch x
.125-inch steel plates on top and bottom of floor bolted together
with at least four 3/8-inch bolts and nuts, or weld main hoop to
rocker sill area with .125-inch reinforcing plates, with plates welded
completely. All 4130 chromoly tube welding must be done by
approved TIG heliarc process; mild steel welding must be done by
approved MIG wire feed or approved TIG heliarc process. Welding
must be free of slag and porosity. Any grinding of welds prohibited.
See illustration. Roll bar must be padded anywhere driver’s helmet
may contact it while in driving position. Adequate padding must
have minimum 1/4-inch compression or meet SFI Spec 45.1. All
cars running 180 mph or faster, SFI Spec 45.1 mandatory.
This is for 11.0 to 11.99,
11.99
By the time a car is capable of running between 11.00 and 11.99 seconds in the quarter-mile, safety requirements are especially important. Up until this point, factory seatbelts are acceptable, but in the 11-second-and-quicker time zone you need a quality safety harness. The minimum requirement is a 3-inch-wide, five-point harness meeting SFI spec 16.1. The 1995 National Hot Rod Association Rulebook outlines the proper way to mount the shoulder harness and belts.
An NHRA-legal rollbar is also required in the category. Recent rule changes have reconfigured what NHRA classifies as a rollbar. The classic four-point bar is no longer acceptable. The new standard is mild-steel tubing of at least .120-inch wall thickness (most chassis companies, like Art Morrison, use .134-inch wall tubing) that includes a forward-running side bar from the main hoop past the driver’s shoulder. This bar is only required on the driver’s side, but most systems include both sides for a six-point rollbar.
An SFI-approved scattershield is also necessary in this e.t. category. NHRA requires the scattershield to have an SFI aluminum-foil sticker. According to Red Roberts of McLeod Industries, older bellhousings can be certified by sending the scattershield and block plate to the original manufacturer. The company will inspect the housing and if it passes, it will receive an SFI 6-1 certification. Most SFI certifications are good for five years. Contact your manufacturer if you’re not sure.
The clutch and flywheel must also be SFI certified. The main consideration in this area is to avoid using a cast-iron flywheel. According to Roberts, sometime in the mid-’70s most of the new car companies began using nodular iron flywheels that are much safer. Most, if not all, current high-performance aluminum and steel flywheels are safe when used in conjunction with an approved scattershield, but the rules state that the pressure plate and flywheel need an SFI certification number. Roberts says the best plan is to record all your SFI numbers in a logbook. This makes it easier for the tech inspector and it shows the inspector that you understand the importance of the inspection process. This e.t. level also requires steel valve stems in all wheels, along with arm restraints for open-cockpit cars like roadsters.