273 Y-pipe?

Here is a pic of the 2bbl and 4bbl Y-pipe design available in early A-body cars. The rusty looking piece is the 2bbl style, where one pipe dies into the other. The 4bbl one shown is an NOS piece and has a "collector" style where both pipes die into one at the same time, but as you can see in the pic, both have to be crushed flat at the end to fit into the collector pipe...not the best for flow. Thats where the Accurate unit differs from the one pictured here. The Accurate design allows the pipe to remain round and die into the collector almost completely unobstructed, save for the fact that both pipes die into the same place and are probably angle cut to fit together and go into the collector as a unit.

The Accurate one is a design improvement over the OE design, but come at a cost. In the end, I still think that the Accurate system is the best overall value, even over duals, but it is a large stroke to pay all at once!!

Hope this helps, geof