Good luck. First find a stretch of road long enough and flat or downhill. No, longer. It's going to take a while! Then hit that stretch with few or no cars. I doubt you could hit 120mph with a stock B23F. I been above 100mph 3 times with a top speed of 105mph (B230F, M47, 3.31, and stock at the time). 110 should be possible, but I just can't see doing 120mph in my car. I suspect weight and wind resistance will play a big part in limiting top speed. Give it a shot and report back.

I bought Z-rated tires purely for the stiff sidewalls! (although they do feel great at high speed)
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Michael -- 1987 244 GT | Volvo 240 Links