Old muscle car. Weight about 3700lbs. Engine a big block with around 450hp. Quarter Mile time is low 13s. Street tires. Mustang Mach-1 2003-2004. Weight is 3450lbs. Horsepower is supposedly around 330. Quarter mile time is low 13s. Street tires.
I know the way they measured horsepower back when differed from now, but some of the times just do not add up.
Could tires have played a significant part and would an old muscle car now using decent tires do better?
There's many things that make todays cars more efficient/faster. One big reason is computer controlled engines and transmissions. Typically, todays cars get much more hp/torque from a cubic inch of displacement. Computers keep an engine's tune optimum under all driving conditions while optimizing shifting for automatic transmissions.
As you mentioned, better tires (and suspensions) are another reason todays cars perform better. Put a pair of modern tires on a muscle car and its times will improve considerably.
Another reas> Old muscle car. Weight about 3700lbs. Engine a big block with
Wasn't it after 1972 they began using SAE NET horsepower rating? I remember seeing the HP figures dropping substantially to figures that made more sense considering the intake/engine/exhaust used. John
The problem was that 1972 was also the year compression ratios dropped in order to facilitate pollution control and this effected horsepower too, so it's hard to reconcile the numbers.
In stock trim most of the old muscle was lucky to get into the 13's, let alone the low 13s. 14's and 15's were the norm. The ones that did run low 13's (we're talking regular production stuff) were tweaked & tuned or were "ringer" cars.
You're right; they don't add up. That's because the 60's horsepower figures were a crock. Most of the figures were sales/marketing driven. So here's what you do. Compare their trap speeds. You'll find, generally, that the really "hot" big-block muscle turned low
100s (less than 103 mph) to high 90s. Some Hemi cars and big-block Vettes ran 104-105. The really "hot" small blocks generally ran mid/high 90s.
I've seen numbers from the Pure Stock Drags and some of those guys are turning 1.8s on bias plys. I'd kill to get 1.8s with my 245/45s.
The big block's forte is prodigious torque, and the old street tires could not hold up to the twist. A switch to slicks could knock anywhere between a half to two seconds off the ET.
By far the best analysis of a 60's car's relative potential is the times turned in the original Stock Eliminator classes. Here, they were properly tuned and devoid of excess weight, and were not allowed headers or slicks. Some suspension work was legal. The problem with magazine test cars is that they were often apples and oranges. Some were heavily optioned so they *looked* good to the testers, and would appeal to the reader who didn't care much about ET's. Stock Eliminator leveled the field.
SAE Gross horsepower ratings are calculated without many of the accessories (such as alternator, water pump, etc.) attached to the engine. After the
1972 model year most manufacturers switched to SAE Net horsepower ratings.
Tires are definitely a big factor in the differences in times - lots of
60's/70's cars used bias tires on 13" rims.
Info for 50 fastest car model years1962-1972 is @
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Info for 50 fastest cars through 1997 model year is @
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Some additional info I pulled a while back off the Mustang Monthly site -
1/4 mile test track times for *STOCK* Mach I Mustangs:
69 Mach I 428 CJ C6 13.9 Car Life 3/69
69 Mach I 351W 4 spd 15.36 Car Craft 1/70
70 Mach I 428 CJ 4 spd 13.8 Sport Car 1970
70 Mach I 351C C6 15.2 Car Craft 5/70
71 Mach I 351 CJ (C) C6 15.0 Hot Car 5/71
71 Mach I 429 CJ-R C6 13.4 Sport Car 1971
71 Mach I 351 CJ (C) C6 15.55 Motor Trend 10/71
71 Mach I 351 HO (C) 4 spd 15.1 Car & Driver 3/72
Regardless of the numbers, given the technologies available in the 1960's and early 1970's, these cars have some very good times. At times, there is NO replacement for displacement...
Like I said before, take these old gross horsepower figures with a grain of salt. Instead use trap speed and vehicle weight... those will give you a better horsepower estimate.
I think if you read this article you'll find the 'Cuda was "tuned" a little to turn a 107 mph trap speed.
But let's just say, for sake of argument, it did turn 107. A 13.10 e.t with a 107 trap indicates a pretty damn good hook for a 3,800 lb car, so I don't think the tires used were holding back its e.t.
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