73 Centurion 455 Horsepower

[Guest]

Hi, anyone know the stock horsepower for a 73 Centurion Convertible 455? There is one on Ebay right now (actually it looks like a steal) and the seller says it has 225HP. Is this correct? I would have thought it was more like 350. Thanks

[rocketraider]

Gross horsepower probably is, even with the post-1970 lowered compression ratios. The 225 hp figure is <span style="font-weight: bold">net</span> horsepower, measured at the transmission with all auxiliary equipment (PS, A/C, alternator etc) installed and running. The carmakers started measuring it as net in 1971, partially to appease the Feds and insurance companies who were trying to lobby and price high performance out of existence. Believe the SAE also had some input, trying to give drivers a more real-world view of what their engines were actually doing.

[Centurion]

Brian L.,

Rocketraider is entirely correct about the horsepower rating for the 455 engine being measured as "net horsepower" beginning with the 1972 models.

Gross horsepower rating of the 455 engine in the 1970 Wildcats -- the Centurion's immediate predecessor -- was 370. Compression ratios were lowered for the 1971 models, enabling the cars to run on low lead or unleaded fuel. The standard 455 in the 1971 Centurion was rated at 315 horsepower, which rose to 330 horsepower with the optional, modified high performance 455. The '72 Centurions, in contrast, were the first to be rated with "net" horsepower, and the rating was 225 horsepower for the standard Centurion 455 and 260 horsepower for the optional version. The book I'm obtaining these figures from shows 225 horsepower for the '73 Centurion 455 and 250 horsepower for the modified high performance 455.

Please keep in mind that, beginning with the '73 models, the 455 engine was no longer standard equipment in the Centurion series, and the base engine became the 350 engine with a four barrel carburetor. The trend for high performance cars was shrinking fast during the early 1970's, and those that remained by '73 were mostly intermediate-size cars. That may help to account for the disappearance of the Centurion from Buick's lineup after 1973, and Buick's concept of a higher performance standard-size car (Century - Invicta - Wildcat - Centurion) seemed irrelevant in the mid'70's marketplace.

It is possible to determine from the vehicle VIN number whether '72 and '73 Centurions were equipped with the modified high performance 455, and a surprisingly high percentage of the Centurions I've observed were so equipped.

[BigFella]

Was 73 the first year for the smog stuff in the engine bay as well? (cat, air pump, etc). This equipment can effect this rating as well...

[Guest brh]

No, 1972 had all that smog garbage too. My Centurion still had horrible gas mileage even with all that garbage disconnected.

[Guest]

Buick's and Mopars were the only ones to have air injection in 1972. That says something about the dirtyness of their engines. Buick had a much better air injection design and it was copied by all other manufactures for their 1973 models.

[Guest]

Air pump yes (easily disconnected, though) cats, no. I believe cats were put on in '74? I can get anywhere from 8 to 18 mpg depending on how I drive and where I'm driving in my '73 225.

[Guest]

Which air pump are you referring to? Is it needed or should I disconnect it? I admit I'm not all that familiar with all the different engine components so please be desciptive as to where it is. I pulled the engine last weekend by myself. Only took about 3 hours. I painted it with the Por15 engine painting kit. I must say, It looks incredible now. Thanks

[Guest]

The air pump/smog pump is on top of the powersteering pump. You can just take the belt off or remove the pump itself like I did. I put a brass cap on the metal line that goes into the intake.