porsche 914, why am i scared of a knocking engine Options

[dlindzey]

looked at a 1.7 the other day
engine rebuilt in 2016 less than 30k miles, fancy pistons seemed like legit job, compressions between 140-150 all cylinders no leak down numbers

2018 or so got rid of the fuel injection system which had recently been rebuilt anyway and went to single carb

since then little issues and tune ups, last shop records this year complained about knocks at start up and variable idle often fast for no reason

i saw the car and drove it not knowing the above and the engine knocking is obvious even to someone of my mechanical inclination, the idle was too fast as well and the fuel pump was loud

would anyone pay top dollar for a car that knocks before you even get it home or is usually a minor thing a decent mechanic can fix--prior shop took a run at it before owner bailed on the car that he had already pumped at least 15k into.

so what is the collective wisdom-car looks good but sounds bad