70-81 2nd gen F body Upper Cowl Sandwich Plate Kit for use with PTFB GEN II G-Braces RACE click for more pics and product details
The upper cowl area where G-braces attach is a ledge consisting of three pieces of sheet metal spot welded together at the factory with a short lip on it. The G brace mounting points are almost centered on the large air openings on the top of the cowl which are the weakest areas. Although the short right angle lip adds a little rigidity to the ledge, the sheet metal ledge itself isn't particularly rigid and you can actually flex the stock ledge with only your bare hands.
Imagine the forces G-braces can exert on the upper cowl ledge during hard cornering, acceleration, braking, or when hitting a bump or dip in the road. There's almost constant pushing, pulling, and twisting forces transmitted by the G-braces as the car is used. When the car is used for auto sports the forces are even greater and quicker than normal street driving. This kit is designed to stiffen the ledge, provide additional resistance to shear stresses, and spread the forces transferred by the G braces to a wider area so that sub frame deflection is minimized which allows the suspension and steering components to work their best.
The race kit is different than the street kit in that the race kit plates that sandwich the cowl on the drivers side are different. This is to compensate for the recessed wiper motor section which flexes more because of the additional leverage the G-brace has on the deeper ledge due to the windshield wiper motor recess in the firewall. The top plate forms a "T" with the cowl face toward the outside and two of the bolts are inside the cowl area adding more rigidity to the G-brace mount area.
The Lab-14 sandwich plate kit eliminates the need to flatten the short lip or use washers as spacers on the ledge where the G-Brace attaches. The steel plates above and below the ledge create a sandwich and are bolted through the pinch welded ledge of the cowl. This stiffens the ledge and spreads the force from the brace over a much wider area which reduces deflection and spreads the forces out to the horizontal sheet metal between the openings on the top of the cowl.
The plates also create a wider thickness for shear forces transferred through the G brace mounting bolts to act on by more than doubling the functional thickness of the ledge when installed. This prevents the G-Brace mounting bolts from tearing the sheet metal ledge or causing the mounting holes to become oblong from the repeated pushing/pulling forces applied by the G-Brace.
This Lab-14 kit does not interfere with use of the stock cowl grill or the stock 70-76 cowl/hood seal.
This race version of the Lab-14 upper cowl sandwich kit is finished in PPG black epoxy primer and includes the 4 plates shown as well as locking mounting hardware including matching hardware for the upper G brace mounts.