I find it a bit difficult to imagine these 2 big sedans in a drag race, that's not what one thinks of when you think of cars like these...

The W116 was really built to be a long distance, luxury, long lasting high speed cruiser - not to be fast off the line, so I wouldn't worry about it.

I heard once that the 3.5 engine was one of the finest engines Mercedes ever built, so I would feel comfortable with that.....

Perhaps a bit of online research might reveal the 0-60 performance times for each engine in that body, and you must know in what state of tune your motor is in.....

Maybe your motor is heavier, and you have lots of items in your trunk which adds weight to make it slower, I can't think why your car should be that much slower than the 280SE, lighter motor, different rear end ratio, who knows?

I wouldn't worry about it so much, just keep your car in good shape

Best,
Jim

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1991 560 SEC AMG, 199k <---- 300 hp 10:1 ECE euro HV ...

1995 E 420, 170k "The Red Plum" (sold)

2015 BMW 535i xdrive awd Stage 1 DINAN, 6k, <----364 hp

1967 Mercury Cougar, 49k

2013 Jaguar XF, 20k <----340 hp Supercharged, All Wheel Drive (sold)