1970 Firebird And 1973 Firebird - Shop To Swap: '70-73 Firebirds

Another difference is that the '70 bumper is a very simple affair to mount, and leaves ample room between the radiator support and bumper to retrieve dropped tools, bolts, etc.

This '73 assembly manual illustration details the five-piece '73 bumper reinforcement assembly. Note that the bumper-BAR ASM PN 488410-is an early '73 part number series. Among the revision notes is one barely visible indicating that this particular assembly manual sheet was revised and redrawn in October 1972. This reinforcing assembly accounts for much of the extra front-end heft of a '73 over the '70-72s. Drop a tool or part down into the valance, and something has to come apart to get it out-don't ask the author how he knows this.

Like the grilles, one item that's definitive of its timeline of usage is the hood latch system. The '70-72 Firebirds used a simple and sturdy steel bar accessible through an opening in the top of the grille housing and driver's side grille itself had a cutout area in its top inside corner to allow access to the latch bar.

The grille opening in the '73 bumper lacks the raised ridge at its rear edge and the Endura portion also continues deeper into the opening as measured here to accommodate the setback of the grille. You could install earlier grilles in a '73 bumper. A '73 grille placed in a '70-72 bumper however, would likely have an ugly gap and leave the raised ridge of Endura material showing.

With the new grille and reinforcement system, or possibly because of the front-impact standard, the '73s switched to a cable pull type that's accessed through the valance opening. (Seen here from a rear view for better detail of the entire assembly.) The reinforcement may have interfered with the '70-72 release, or it might not have met the new standard. Only Pontiac's engineers know.

In addition to the '73's reinforcement structure came a fender brace, officially known as the "radiator baffle brake" on the assembly manual sheets. It appears to have been made from leaf spring steel. It is of the exact same width and thickness and has the same side radius as the leaf springs on the author's '73 Formula. The brace was found to have a gun-blue type of original finish under the paint, the same type of protective coating usually found on leaf springs. If you need to make replacements, at least you know an easy-to-find source for the correct stock material.

Additionally, the core support bushing changed from the smaller version, used from '70-72 to a larger version, used only in 1973. 1974 and later cars returned to the smaller style.

Of course the fender brace in turn required a new core support top (lower) shown here compared to a '72 version (upper).

At the front of this comparison photo is the lower half of a '73 core support. It has a much narrower cut on the passenger's side, seen in contract with the '72 core support immediately behind it.

Another item that changed on the core support, most likely because of the new impact standard, was the manner of securing the battery hold down bracket. The '70-72 versions were spot welded to the rear of the core support.

The '73 core supports have a slot cut in them that the vertical portion of bracket passes through. Tabs on the bracket rest against and are secured to the front of the core support.