Knurled pistons can work very well ,, in the right situation .
It is an excellent fix to save money and not have to bore, or buy new pistons .
To be really effective for a long time,,,it should be concentrated on the minor thrust side of a piston .
That way ,it doesn’t see the full load against the cylinder wall and won’t wear off easily .
It basically just acts to take up clearance in the cylinders,,,and keeps the piston from rocking in the bore .
Usually you are only talking about 5-6 thousandths knurl height at the most ,,depending on the condition of the pistons,,and bores .
As long as the bore taper is not excessive,,,it will work for quite a while .
Using oversized, file fit rings goes a long way in helping oil consumption as well .
Of course,,,we are only talking about an everyday street engine,,,mostly a daily that needs to help keep food on the table .
This is not for a performance application .
I’m sure Smokey was pulling someone’s chain .
He was the Master of deception,,,,,fooled NASCAR many times,,,,and only told his secrets later towards his death .
What a Great engine man !
Tommy