Really I thought the 455 that appeared in the 71 firebird-trans am was a 428 pontiac motor with an increased bore. Dubbed the 455-HO and later SD-455 in 73/74.
Oh and I want a V-mount:bump:
That's exactly what I thought, because I had a friend with a white T/A back then, that I think was a 73' model & could of swore it had a 455 in it. But, I did a quick search on the internet after sleay brought it up & only showed 400HO for Firebirds & T/As for that time frame.
Just did some more research & found this:
"For the first time since 1970, two engines were offered in the 1973 Trans Am, both displacing 455 cubic inches, in base and Super Duty versions. The engines might have offered the same displacement, but that is where the similarity ended. The base engine (coded as follows - manual WT, WW, ZZ, and, ZE and for the automatics - X7, XE, XL, XM, YA, YC, and YD) produced 50 fewer horsepower than their round ported 1972 H.O. counterpart. Horsepower was [email protected]
rpm while peak torque took a hit as well, dropping to 370 lb/ft @2800 rpm. Increased emission regulations meant a drop in the compression ratio, now down to 8.0:1. The output of oxides of nitrogen (large displacement engines are more succeptable to high levels of N0x as compression ratio's increase) were lessened with a lower compression ratio. Pontiac removed the H.O. designation from the engine, and simply badged the shaker with 455 engine calouts."
Here's the website: http://www.2gta.com/1973ta.html