Factory Horsepower Rating-how accurate?

[ANDYS87]

I recently bought an 87 Grand National, the car I've wanted since highschool! It seems like these cars are a little more powerful than the factory advertised 245 HP. Does anyone know if this figure is accurate? Or did the factory under-rate them for insurance reasons? I think a car magazine once dynoed a stock 87 GN and said the HP was more like 275??? I would appreciate any info. Thanks

 

[azgn]

Buick rated them the same as the Corvette for political reasons.....prolly closer to 300 FW

 

[Blown&Injected]

It might be accurate but less than honest. I think it is rated at something like 4,100 RPM's. GM just failed to mention the HP at say - 5,700 RPM's.

 

[EightSecV6]

I dyno'd EvilGn's bone stock GN with 8,000 miles on it, I dont remember the exact number but after the chassis correction it was REAL close to the 245HP at the flywheel.

 

[turbofish38]

The real reason for the 235/245HP rating was because of the transmission. The only trans available at the time was the THM200-4R and Hydramatic division could only beef it up to a certain torque rating. The Buick engineers fudged on the figures a little so they could get the trans and build the cars. We all know or heard of the horror stories about certain TR's and the weak links associated with this trans. Also the BRM has the stoutest list of parts out of any of the 200-4R's which also supports this fact. We all know if GM could save a penny on something they would do it. It was cheaper to do this than to retool and make a special version of another trans like the THM700-R4.

 

[JDSfastGN]

Most GNs ive heard of that were dynoed bone stock were in the 200-230 range with absolutely no modifications and a good rune. What really gets them moving and feeling fast is that its still putting out 320 lbs of torque to the rear in stock form. But yes the given reasons for the 200-4r and political reasons because of the vette are both reasons why it may be slightly underated.