The tech data for a 89 Firebird shows a 230hp and a 240hp 350. My Formula 350 does have the 3.27 rear and dual Cats. Would that be the only difference or is there a different cam in the 240 hp vs the 230hp?

JP

 

As I recall the 240HP cars were 1989 cars. I do believe they got a slightly larger cam from that point on. In 1990 they got another small boost due to speed density TPI. (245HP/345TQ)

 

I researched published horsepower figures for 1991 in depth. What I found was that Pontiac was all over the map advertising the horsepower numbers. One minute they'd say 230, the next 235, the next 240 or 245. While this applies specifically to 1991, it's pretty safe to assume that other years were similar. Part of the problem is the standard practice of rating the Firebird 5hp less then a Camaro with the exact same engine. In reality, the engines were assembled before they were even assigned to Camaro or Firebird, they're exactly the same.

So then what is the actual horsepower rating for a 1989 Formula with a L98 and 3.27 gears? By Pontiacs rule book (the -5hp for being a Bird) it'd probably be 235hp. In reality, it's probably safe to say 240. Also since these cars were mass produced and the drivetrains weren't blueprinted, the margin for error between the rating, car to car differences, and so on are probably greater then +/- 5hp.

 

Dual cat 350 cars got the exact same cam as same-year single cat 350 cars. This doesn't hold true for 305s with automatics.

 

For 1989, the 10-hp difference is from the N10 dual cat exhaust option.

According to the product book for that year, the 5.7L TPI was rated at the same 225 hp as in 1988; the N10 option (available beginning on October 1988 production units) added the 10-hp gain to a total of 235 hp.

The product book for 1990 shows the exact same figures as above.

For 1991 the total jumps to 240 hp on the 5.7L TPI, which included the mandatory Performance Enhancement Group.... which in turn included the dual cat exhaust.

The 1992 figures are the same as those listed for 1991.

So apparently along the way between 1990 and 1991, another five horsepower was eked out there somewhere.

 

I read on austinthirdgen.org that the additional 5 hp came from lighter pistons but it said that happened in 1990

 

As for the 1989 HP discrepancies... It has pretty much been covered, but keep in mind that the N10 dual cats was original only on the Formula, mid year they started putting the system on all L98's and LB9/M5 (Pontiac) cars... More so, I am not sure if all Formula 350's and LB9/M5 cars got it as well, as some have said that early cars did not get N10... Also the difference between the IROC and the Firebird with the L98 & LB9 was the air intake system, obviously the Firebird was slightly more restrictive. The Firebird also weighed more and to explain that the Firebird over a camaro may feel slower may have been explained thru literature as a slight HP change... Head to head I have never seen anything that suggested that a L98 Firebird was any difference performance wise than an IROC of the same year.

ALSO you may consider that Chevrolet may have over-bloated their HP estimates more than Pontiac, OR Pontiac may have under emphasized its HP estimate. There was not a standard of hp rating as there is now, as SAE, or ASE is now certifying GM's HP claims on their engines... This was not always the case, and until recently there was no industry standard of HP...

AFAIK the engines and its parts, cam, crank, heads, pistons, connecting rods, etc were the same from 1990 - 1992... At least the last time I looked the replacement part numbers were the same...

I actually suspect that the increase in HP from 1990 to 1992 was improved ECM Program management, as everything else appears to be the same... It is not too difficult to squeeze an extra 5hp from a new program...

John

 

At least some LB9/T5 equipped Firebird Formula cars did indeed get N10. According to Compnine, my car was an earlier production 1992 model year car built on 10/28/1991. At the very least my RPO codes confirm the car came with N10, LB9 and MK6.

 

ALL 1990 - 1992 LB9/M5 Formulas & GTA's got N10... NOTE: Trans Am & Z28, N10 was an option with the LB9/M5.

ALL 1990 - 1992 L98 Z28's, Formula 350's, L98 GTA's & L98 Trans Am's from 1990 thru 1992 got the N10 Dual Cats...

I have yet to officially find an exception to the above rule... Compnine (no matter how futile or useless some think it is agrees)

1989 however is a different story, it seems that many did not get the N10... It should be noted There were no N10 cars in 1987 & 1988...

 

Good to know.