The maximum CR for 3.9 pistons I can find is 9.35 OEM pistons? Why is this so low when one can get higer compressions for the 3.5?
What pistons do I use if I want a higher compression than this?
Stupid question about 3.9 compression ratios
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I would imagine that the compression ratios / pistons available as OEM would reflect the application that the engine was originally intended for,..ie powering a Land Rover or Range Rover.
Aftermarket companies may well use these engines, but their primary role , the one that they were manufactured for, was to power four wheel drive vehicles, with substantial low to midrange torque, as opposed to top end power.
The fuel and emission requirements in many countries into which these vehicles are sold would also mean that lower CRs would be required.
The higher CR OEM pistons were available when the 3.5 litre engines were being fitted into cars made by Rover.
The Rover P5B and P6B had pistons with 10.5 : 1 CR, only up to 1973 or there abouts, after that date the piston design was changed with the CR dropping to 9.25 : 1.
The Rover 3500 Vitesse from the early / mid 1980s used pistons with a 9.75 : 1 CR.
Aftermarket companies may well use these engines, but their primary role , the one that they were manufactured for, was to power four wheel drive vehicles, with substantial low to midrange torque, as opposed to top end power.
The fuel and emission requirements in many countries into which these vehicles are sold would also mean that lower CRs would be required.
The higher CR OEM pistons were available when the 3.5 litre engines were being fitted into cars made by Rover.
The Rover P5B and P6B had pistons with 10.5 : 1 CR, only up to 1973 or there abouts, after that date the piston design was changed with the CR dropping to 9.25 : 1.
The Rover 3500 Vitesse from the early / mid 1980s used pistons with a 9.75 : 1 CR.
4.6 Rover 3500 P6B
