The Gapp & Roush race car known as the ‘Taxi’ was built to take advantage of the NHRA rules in effect.

The story itself is a bit twisted both in actual history and in the re-telling over the years.

Let’s see if I can lay out a straight line…so to speak.

First…the rules

In 1973 NHRA Drag Rules the NHRA mandated weight per cubic inch facteos for Pro Stock vehicles were:

• 6.50 or more lbs. per cubic inch, for original “true wedge” or incline valve engines.
• 7.00 or more lbs. per cubic inch, for all other engines.

Additionally, the rules stated:

• ENGINE, 100 lnch Wheelbase or More: Must be of 1965 or later manufacture and must be the same make as car. Any internal modifications permitted. Minimum total car weight, 2,400 lbs.
• ENGINE, Less than 100 Inches Wheelbase: Must be of 1965 or later passenger car production, the same make as car, with original displacement 366 inches or less. Any internal modifications permitted. Minimum allowable weight 2,100 lbs.

Seems pretty straightforward. A legal NHRA small block car would weigh, assuming a engine displacement of 366 cubic inches, 2379 lbs.

A big block car, say a Hemi, would have weighed around 2982 lbs.

An extra 603 pounds was a killer for the big blocks. It becomes obvious why the small block cars were so successful during the 1973 season (in fact continuing their success from 1972).

As my Dad stated in a interview:

Problem was, if NHRA had consulted their physics books they would have realized that it wasn’t all that straightforward. There was a thing called inertia, which no one took into consideration. Simply stated, if you take a 2,700-pound big-block car and a 2,300-pound small-block car and you let out the clutch on each one, it’s the inertia off the line that determines the performance during the first 60-feet of the pass, not the horsepower. In other words, if you kick a cement block and a block of wood, guess which one will travel the farthest? So, naturally, Jenkins’ little Vega just jumped off the starting line and consequently it killed the Chryslers during the 1972 season.”

Going into 1974, needless to say, there were a few complaints. So NHRA tried again.

The 1974 Drag Rules state the following:

• 6.45 or more lbs. per cubic inch, for cars with 105 inch or more wheelbase using true wedge or incline valve engines of original production.
• 6.65 or more lbs. per cubic inch, for cars under 105 inch wheelbase using true wedge engines of 366 cubic inches or less, original production.
• 6.75 or more lbs. per cubic inch, for cars under 105 inch wheelbase using incline valve engines of 366 cubic inches or less, original production.
• 7.00 or more lbs. per cubic inch, for cars over 100 inch wheelbase using all other engines, i.e., Hemi’s, Cammers, etc.

Lastly the weight minimums:

• WEIGHT MINIMUMS: All cars with 6.45, 6.65 & 6.75 factors = 2,100 pounds. Cars with 7.00 factors = 2,300 pounds.

Reading THOSE rules and representing Ford vehicles a few things pop out:

• Weight Minimums for the big block cars were lowered by 100 lbs.
• A car with 105″+ wheelbase has a significant advantage of .55 lbs. per cubic inch over the big block cars and .20 lbs. per cubic inch over the next classification.
• Ford didn’t make any recently manufactured two doors that were over 105″ that could be used. In fact, the 2-door Maverick was probably considered in the rules as the its wheelbase is 103″.
• The 4-door Maverick, however has a 109″ wheelbase.

So a legal NHRA small block car over 105″ wheelbase would weigh, assuming a displacement of 366 cubic inches, 2360.7 lbs.

A Pinto would weigh 2433.9. So, that is 73 lbs. MORE than the Maverick with the same engine.

A big block car, say a Hemi, would have weighed around 2982 lbs.

The weight advantage of small block (at 105+ inches of wheelbase) vs. big block has gone UP to 621.3 lbs.

So..what happens? NHRA decides that the advantages provided for in the 1974 season need to adjusted. So they go insane adding complexity to the rules in the attempt to achieve parity. At this point, the rules are out of hand.

I have included the relevant set of rules below. See here for all the engine rules.

The new rules state:

• Over 105″ 105″ or less Manufacturer and original engine size
• 7.10 7.30 Ford Cleveland (Small Block) 302 & 351
• 6.90 7.10 Chevrolet (Small Block) 302 & 350
• 7.30 — Chrysler Corporation Hemi & Ford SOHC (Big Block)

The Ford vehicles just got jacked…and the Pinto’s got hammered.

Let’s run our weight calculations again:

• Ford – 366 * 7.10 = 2598.6 lbs.
• Chevy – 366 * 6.90 = 2525.4 lbs.
• Chrylsler – 426 * 7.30 = 3109.8 lbs.

In 1973 a small wheelbase Ford could run at: 2379 lbs.

In 1974 a Ford long wheelbase car could run at: 2360.7 lbs.
In 1974 a Ford small wheelbase car could run at: 2470.5 lbs.

In 1975 a Ford long wheelbase car could run at: 2598.6 lbs.
In 1975 a Ford small wheelbase car could run at: 2671.8 lbs.

In 1975 a long-wheelbase small-block Chevrolet could run at: 2525.4

In 1975 a Chrysler Hemi could run at: 3109.8

The difference between the 1974 weight and the 1975 weight was 237.9 lbs. In closing, the performance of the Taxi during 1975 is downright amazing given the attempts by NHRA to factor the vehicle.