1973 Pontiac Firebird Formula 455-SD

oldskool · 12-17-2021, 05:31 PM

A guy just posted this on a Pontiac forum.

"...Initially NHRA had the SD in G/SA..."

Does anybody here know if this is true ?

If it is, then the H&M T/A may have been running the SD455 engine, when it was marked G/SA.

But, John Clegg won D/S @ Indy '73, in his '73 SD455 Formy. So, if NHRA began the '73 season classing the SD455 T/A in G/SA, looks like they added hp to the SD455, in just a few months.

Can anybody here check this out, to find the exact dates in '73 when NHRA changed the hp factor on the SD455 combos ?

Could they have maybe begun the season using the factory net rating of 290hp, then increased it very early in the season ? Or ?

Would really love to know the exact timeline of all hp factor changes to the SD455 combos, during the '73 season.

I've posted that the H&M '73 T/A was running a D-port 455, when it was classed G/SA. But, it MAY have been SD455 powered, the whole time.

Anybody here know about this ?

12-17-2021, 05:31 PM	#20
oldskool VIP Member Join Date: Dec 2014 Location: The Land of Bayous, Boudin & Crawfish Posts: 1,668 Likes: 223 Liked 747 Times in 362 Posts	Re: 1973 Pontiac Firebird Formula 455-SD A guy just posted this on a Pontiac forum. "...Initially NHRA had the SD in G/SA..." Does anybody here know if this is true ? If it is, then the H&M T/A may have been running the SD455 engine, when it was marked G/SA. But, John Clegg won D/S @ Indy '73, in his '73 SD455 Formy. So, if NHRA began the '73 season classing the SD455 T/A in G/SA, looks like they added hp to the SD455, in just a few months. Can anybody here check this out, to find the exact dates in '73 when NHRA changed the hp factor on the SD455 combos ? Could they have maybe begun the season using the factory net rating of 290hp, then increased it very early in the season ? Or ? Would really love to know the exact timeline of all hp factor changes to the SD455 combos, during the '73 season. I've posted that the H&M '73 T/A was running a D-port 455, when it was classed G/SA. But, it MAY have been SD455 powered, the whole time. Anybody here know about this ? Last edited by oldskool; 12-18-2021 at 12:18 AM.