Under-rated muscle cars?

[Eric]

For those of you who caught his post on this subject, Pete raised an interesting point about the late '70s Trans-Am with the "T/A 6.6 litre" 400 V-8. His observation was that this engine - which was factory rated at 220-hp - had to have been considerably under-rated given the car's 1/4 mile times and speeds. I think he's spot on.

Another example: The mid-'80s Chevy Monte Carlo SS (and Camaro Z28 with the same basic engine, the L69 305 "HO" V-8). Both cars were rated at 190-hp, max. Yet these heavy (appx. 4,000 lb.) cars still were capable of high 15-second quarters in stock trim .., which, again, strongly suggests their factory hp rating was way off.

I drive brand new cars with about the same (or slightly more) power and they do not feel anywhere near as quick or powerful. A good example - the current Ford Five Hundred. Its V-6 is rated at 200-hp, so it's supposedly more powerful than the old Monte's 305 V-8. But the Monte was a quicker car... .

Seems fudging the hp numbers was not exclusively a '60s thing!

[Disco Man]

Very Good Topic! Having spent my teen years during the 1980s, these cars bring back so many fond memories. All the high performance G-bodies were underrated during this period. As you said a L69 Monte Carlo SS which weighed about 4,000 lbs was good for high 15 second 1/4 mile times (with mandatory automatic transmission). The Trans Am and Z28 with the L69 H.O. hit the 1/4 mile in low to mid 15 second range with the Borg Warner T5 (and mid to high 15 second range with the automatic transmission). What made me laugh was GM rated the Monte Carlo SS (L69) at only 180 horsepower. According to them it was due to the Monte Carlo only having a single snorkel aircleaner while the Z28 had the dual snorkel aircleaner. However the L69 Trans Am only had the single snorkel aircleaner and it had a GM factory rating of 190 horsepower.

Never-the-less either way the 180 and 190 horsepower ratings were underrated for all three of these cars. Proof of this was the '86 (Grand Prix) 2+2 aero coupe which on paper it's LG4 305 was rated at 165 (only 15 horsepower less than the '86 Monte Carlo SS's 180 horsepower). Yet it was over a second slower in the 1/4 mile (17 seconds) than the Monte Carlo SS aero coupe (high 15 seconds). Both cars weighed the same and were built on the same platform, a 15 horsepower gain would never yield a gain of a little over a second in the 1/4 mile for a 4,000 lbs car.

The hidden gem with the L69 305 was that the engine block was reinforced with thicker walls and came with a pretty hot cam (taken from the L83 350 which powered the Corvette). The LU5 cross-fire 305 used the same hot cam and used the same reinforced thicker wall 305. Both the L69 and LU5 had a 9.5:1 compression ratio (which for the 1980s was pretty high, and required high octane unleaded gas).

Besides the L69 cars, here's some other greats from the 1980s:

1) 305/350 1985 - 1992 TPI f-bodies (Camaro/Firebird) - 305 TPI rated from 190 - 245 horsepower. Fudging of the figures occurred here also, remember the '87 Trans Am GTA with TPI rated at 210 horsepower which had same 350 TPI motor as the '92 GTA which was rated at 245. Both cars had the same 1/4 mile times (only difference between the two GTAs was the '92 had the dual cats).

2) 1985 Mustang GT/LX & Mercury Capris RS (with the 305 H.O. 4 bbl V8 rated at 210 horsepower) - This was the first high performance roller cam 302 and the last of the 4 bbl 302s. It was underrated, my cousin had a '85 Capri, this car felt like it had at least 60 horsepower more than '84 302 H.O. which was rated at 175 horsepower.

3) 1989 3.8 liter SFI Turbo 20th Anniversary Trans Am (250 horsepower, yeah right). This car got solid high 13 second 1/4 mile times with muscle car era trap speeds. Many experts believe the true flywheel horsepower rating was well over 300 horsepower.

4) 1984-1985 (302 H.O. TBI) LTD LX: The LTD LX was a lot of fun and Ford had the right idea with this car. They wanted a V8 powered 4 door car that had European flair and could compete with the rwd 4 door touring sedans from Europe. GM's strategy at this time was to compete with the souped up FWD a-bodies like the Pontiac 6000 STE. Though the Pontiac STE was quick it still as an example was rated at only 130 horsepower (2.8 liter V6 MPI), but it garnered all the press, Car & Driver gave the STE its 10 best award a few years in row during this time. The LTD LX was a lot more fun to drive, and in the end it will be worth more money as the years progress. As a side note these LTD LX's horsepower figures were a little underrated (the '84 was listed at 165 horsepowere and the '85 at 175 horsepower by Ford however the engines and transmissions were identical for both years). Where Ford went wrong was not continuing the rear wheel drive roomy 4-door touring car. Ford like GM got side tracked for 20 plus years on the fwd (front wheel drive) drug trip. However it appears Ford may be getting the picture, here's a modern version of the Ford LTD LX, in the form of the new rwd (new 5.0 cammer V8) Ford Interceptor Concept car:



5) 1986 - 1993 (302 H.O. EFI powered) Mustang LX/GT & Lincoln Mark VII LSC: These cars need no introduction, they also had their horsepower underrated from the factory. They were also fun to drive.

6) 1986-1987 Buick GN (3.8 liter SFI turbo V6 with intercooler): these cars are legendary, with much much more horsepower on tap than their horsepower ratings (230 for '86 and 245 for '87) suggested. Buick GNs could hit low 14 second while some tests had them in high 13 second 1/4 mile time range back in the day. Their true horsepower rating is similar to the '89 Turbo Trans Am (which had slightly better heads).

7) 1984 - 1987 (high performance) Olds G-bodies (442 & Hurst Olds): These cars were underrated and usually obtained 1/4 mile times on par with the Monte Carlo SS. They all were powered by the Olds 5.0 liter 4bbl V8 (307 CID) H.O. which was factory rated at 170 to 180 horsepower (depending on the year). I test drove back in 1987 when I worked at an Olds dealer both a new '87 442 307 4bbl H.O. (170 horsepower) and a new 2 door '87 Cutlass Supreme Salon (standard 307 4bbl rated at 150 horsepower) - both were identical in weight and both were equipped with 200R4 automatic transmissions. The difference on paper was 20 horsepower, the real world difference was the 442 with the 307 4bbl H.O. felt like it had at least 60 more horsepower.

[Eric]

Hi Pete,

Again, thanks for taking the time to reply so comprehensively!

It'd be a great story to find some stock examples of the cars you listed and do dyno runs with them to find the real-deal horsepower these cars delivered.

I have no doubt your estimates of the difference in rated vs. real hp are pretty close. A good way to get a feel for it, from my point of view, is to consider modern performance cars that weigh about the same, how quick they are - and what their hp ratings are relative to their '80s-era counterparts. A new Mustang GT, for example, is a high 13 second/low 14-second car - with 300 hp (rated). This is about the same performance that a turbo 20th anniversary Trans-Am delivered (it was actually quicker) with "only" 270 rated hp.

I would bet the 3.8 liter/turbo-equipped Trans-Am delivered at least 310 hp....

Just one example!

[Disco Man]

Eric,

I'll see what I can do. I'll go through and compile some performance figures for some of these 1980s musle cars and use a horsepower calculator to calculate their estimated flywheel horsepower. I post something in the next few days.

[Eric]

Eric,

I'll see what I can do. I'll go through and compile some performance figures for some of these 1980s musle cars and use a horsepower calculator to calculate their estimated flywheel horsepower. I post something in the next few days.

Groovy!

[swamprat]

Let's keep in mind that 1980s cars were lighter than todays versions, so they could go places with less horsepower.

[Eric]

Let's keep in mind that 1980s cars were lighter than todays versions, so they could go places with less horsepower.

Well, yes and no. The '80-'81 Trans-Ams were porkers - 4,000 pounds, easily.

Pete's '79 TA is no lightweight, either. Yet it is a low 15-second/high14-second car, with an engine that supposedly puts out only 220 hp. I think Pete's absolutely right that the engine was under-rated and that its actual output is closer to 260 hp....

[Dave Brand]

I have no doubt your estimates of the difference in rated vs. real hp are pretty close. A good way to get a feel for it, from my point of view, is to consider modern performance cars that weigh about the same, how quick they are - and what their hp ratings are relative to their '80s-era counterparts. A new Mustang GT, for example, is a high 13 second/low 14-second car - with 300 hp (rated). This is about the same performance that a turbo 20th anniversary Trans-Am delivered (it was actually quicker) with "only" 270 rated hp.

I would bet the 3.8 liter/turbo-equipped Trans-Am delivered at least 310 hp....

Advertised BHP figures aren't always based on reality! 'Top Gear', the UK TV programme, tested a new Shelby Mustang GT500 this week. They didn't think it performed like a 500BHp car, so they put it on a rolling road........450BHP! Richard Hammond, one of the presenters, has a GT400, said by the dealer he bought it off to be a good one - that made around 250!

Another criticism they made of the GT500 was the decision, on cost grounds, to use the rigid rear axle. It certainly looked a handful round their test circuit - a Roush Mustang, on the other hand, handled much better; even American cars handle better with IRS!

[Disco Man]

swamprat,

The '80s cars that I mentioned weighed at least 3,500 lbs or more and most would out weight their counterparts today. The only exception I know to this is the the 1985 Monte Carlo SS which weighed around 3,500 lbs, a new 2007 Monte Carlo SS has a weight of around 3,500 lbs (both cars are V8 powered). A '85 LTD LX weighed in around 3,500 lbs or more and a 2007 Ford Fusion weighs around 3,100 lbs (the Taurus replaced the LTD and the Fusion replaced the Taurus). These rwd V8 powered cars by no means were light, most of these cars were built on platforms designed in the 1970s.

[Disco Man]

Dave Brand,

Very true. Horsepower figures are not always what they seem, and automakers have been cooking them, like Enron cooked its books for years.

As for IRS, it's not always better. My guess is that the new GT500 Cobra has IRS due to the fact that a solid axle is better for drag racing. A lot of GT500 owners will be taking their cars to the 1/4 mile track. IRS has never had many fans in the 1/4 mile drag racing, talk to the old timers this was their main complaint with Corvettes (IRS). As for handling IRS systems tend to be better handlers on the oval track, however I have seen some solid rear axle cars with some great handling numbers if the suspension is well tuned. Where IRS reigns is on the bumpy pothole infested roads. The rear on a car stays planted to the surface better with IRS in these bumpy conditions.