Does anyone know of any tests showing realistic top speeds of the various engine combos? All the tests I've seen are with cars using short gears (eg. 3.90s) which results in pretty low top speeds due to being rev limited.
Kinda silly to say that a RA II car is only capable of 115 mph when it gets to 108 in a 1/4 mile. I know I've taken my '69 well into the 140 mph range with 2.56 gears and an essentially stock RA III engine.
There really is no true high speed test based on engine. The top speed of any vehicle can be calculated based on vehicle specs.
RPM x rear tire diameter x .0029749 / rear gear ratio (assuming the trans is a 1 to 1 high gear)
In your case if you max out at 5500 rpm with a 2.56 ratio and say a 27” tire = 172mph top speed theoretically.
Same with a 3.90 gear = 113MPH
The top speed can also be limited by having the available HP to overcome the aerodynamic drag of the vehicle and frontal area. You may top out on power before ever reaching that top speed - thus this is the only time the engine might come into the equation (based solely on the higher available HP if needed).
