Ireland & MM both sell single row timing chains with the nod towards reduced rotating mass. I agree there could be longer life with a dual row chain, but if your spending $$ to squeeze a little more power out of an M42, single row is just another option. BMW did use single row on M10‘s in 320i & I’ve heard of more than a few 2002 owners who have single row chains with no problems. Dual row is overkill, IMO.
Here is what MM says:
For years we have used single row timing chains on the M10, M30 single overhead cam engines. They have proven to be extremely reliable to the point where we trust them more than the Double row chain. Yes the dual row is physically stronger but due to the centrifugal force of the spinning chain, the sheer mass of the double row chain can cause the chain links to stretch and wear out and the chain’s whipping action can also cause excessive wear on the guide and tensioner rail. Converting to the single row chain reduces the rotating mass of the chain and sprocket by about 2 lbs and to-date we have never had a chain failure from this modification.
