Firebird Transam 455 SD

[MrPbody]

Yes, meant '73. Sorry for the fat fingers.
The '71 and '72 HO engines were advertised at 335 horse (gross). The '73 SD was advertised at 310 (net). The '74 SD was advertised at 290 (net).
'69 and '70 Ram Air IV and '70 455 HO were rated at 370 (gross).
Regardless of factory ratings, the 455 SD was the most powerful engine made after '70 (production in ANY American car) until the late '90s. Only now, are we approaching the true power output of that engine, with all the modern technology. SD was a great project. Just wish some had found their way into GTOs and the aftermarket. What a crate motor that thing would be today! A 72 CC version of that cylinder head would sell like there's no tomorrow! The large chamber is the reason it never caught on with the racer crowds. Pontiac engines don't react as well to domed pistons as other engine families.

[volkerc]

Originally Posted by MrPbody

Yes, meant '73. Sorry for the fat fingers.
The '71 and '72 HO engines were advertised at 335 horse (gross). The '73 SD was advertised at 310 (net). The '74 SD was advertised at 290 (net).
'69 and '70 Ram Air IV and '70 455 HO were rated at 370 (gross).
Regardless of factory ratings, the 455 SD was the most powerful engine made after '70 (production in ANY American car) until the late '90s. Only now, are we approaching the true power output of that engine, with all the modern technology. SD was a great project. Just wish some had found their way into GTOs and the aftermarket. What a crate motor that thing would be today! A 72 CC version of that cylinder head would sell like there's no tomorrow! The large chamber is the reason it never caught on with the racer crowds. Pontiac engines don't react as well to domed pistons as other engine families.

red book differs on your figures, not familiar with the gto engines, and as far as engines are concerned, there is plenty of movement with more and more companies building some great engine castings, for those who have the money.... you can get brand new castings of pontiac engines with improvements over the stock blocks...

[Gunstar1]

1973 S.D. 455 = 310 HP
1974 S.D. 455 = 290 HP

These are net numbers. It was one of the last production 13 second cars until the 1986-1987 Grand National

[volkerc]

Originally Posted by Gunstar1

1973 S.D. 455 = 310 HP
1974 S.D. 455 = 290 HP

These are net numbers. It was one of the last production 13 second cars until the 1986-1987 Grand National

And where did you find those numbers? All my literature is telling me 290!?

[Gunstar1]

Originally Posted by volkerc

And where did you find those numbers? All my literature is telling me 290!?

www.firebirdgallery.com

And

Chilton Auto Manuals

I think I had read it in a High Performance Pontiac magazine a few years back, as well.

[volkerc]

Originally Posted by Gunstar1

www.firebirdgallery.com

And

Chilton Auto Manuals

I think I had read it in a High Performance Pontiac magazine a few years back, as well.

It's getting interesting here. I checked again some of my literature, one Gunnels Firebird Buyers Guide also lists 310 hp, Then "Fabulous Firebirds " also says 310 hp, so I went to the real specialty book, "Pontiac Musclecar Performance 1955-1979" by Pete McCarthy, which has the most comprehensive Engine Codes and part numbers listed, where I now quote, page 51:

"On March 15,1973, the EPA mandated a major change in Pontiacs exhaust emission system. Essentially, the changes involved removal of a solenoid in the EGR system which rendered the EGR system inoperative.as part of the agreement, all engines were recoded according to the chart below, and included all engines after Serial#532727.A casualty of these changes was the 310 HP 455 SD engine (X8,Z8). No 455SD Firebirds were released to the public prior to April, 1973."

INTERESTING isn't it? It basically means that Pontiac had the car advertised with 310 hp, but because of emissions had to cut it back to 290 HP, and therefore never released a 310 HP car to the public!

[hotrod_chevyz]

Yeah it is getting interesting cause some of pontiacs own information clashes with itself.I was just looking and in some cases they even mislabeled the spark sequence.They lied and said 18736542 instead of 18436572.Not only that but ive found head valve and cc contradictions dating so far back that perhaps even later printing modeled after these were incorrect becuse a flaw in the original data.


Also interesting,A few of the 310 hp cars did actually hit the streets because they was already pressed and in shipping and by contract pontiac had to fulfill a few written agreements.Back then high proformance cars were all just about back ordered somtimes years and ive heard a few sources claim because of that fact even more slipped through the cracks only mislabeled.