C414 pilot reported they shut one engine down after hearing a loud noise and observing smoke and diverted to a nearby airport.

Narrative

Starting with the leg at ZZZ; I had stopped to get fuel at the FBO. They topped off the main (tip) tanks and the auxiliary tanks. I did verify on their truck and with them that it was 100LL they were adding. While they were fueling; I went inside to pay and let the passengers know that once they fuel and I preflight we could leave when they were ready. After paying; I went out to the ramp to preflight. I verified the fuel levels and sumped all 4 tanks to ensure there was no debris or water. There was no indication of issues with this. I checked oil levels on both engines which read about 9.5 quarts each. I continued to preflight by checking the lights; flaps; and airframe and found no issues. About 30 minutes later my passengers arrived and we started up. I received the weather and my IFR clearance at the ramp and proceeded to get a taxi clearance from ground. During this all instruments were operating within normal limits. I conducted a run up holding short and all mag drops; vacuum; alternators were normal. Once cleared for takeoff; I lined up; held the brakes and increased power to 30' of manifold (full props; full mixture). Once I had verified engine instruments were normal and there were no fluctuations with the RPM/Manifold Pressure I advanced the throttle to full. This gave 2700 RPM and 38' as normal and I released the brakes. During the roll; I verified that engine instruments were green and normal; airspeed was alive; and my heading matched the runway. At 105MPH I rotated and climbed to 500' where I pulled the throttles to 33' and RPM to 2500. At 700' I made my left turn on course as per my clearance. I was transferred to approach where I was cleared from 8;000' to 20;000'. I continued the climb under these engine settings and kept the EGT at 1450 per the RAM chart. I was given an expedited climb for a Cirrus going the opposite direction and I raised the nose to capture 120 MPH (previously cruise climbing at 140) and maintained my EGT. During this all instruments were still under normal conditions. Once clear of traffic I resumed my previous cruise to 20;000'. At about 5 degrees celsius I closed the cowl flaps. At cruise altitude I referenced the RAM performance chart and pulled the throttles to 29-30' of manifold and RPM to 2400 (I believe this was the setting; but I just abided by the chart for 20;000' at about standard conditions since it was within a few degrees.) I leaned the mixture to get around 21.5 GPH at the suggested EGT per the performance chart. For the next 10 minutes; the oil pressure; oil temperature; cylinder temperature were green and normal. Along with this; the pressurization was well below red line and we were at about 9;000' cabin pressure. Around 10 minutes after cruise I heard a loud pop; and immediately reduced throttle about half way on both engine and looked at all of the instruments and fuel flow. Nothing looked far outside of normal but when I looked out the left window I noticed smoke from the cowling and immediately proceeded to secure the left throttle; left prop lever; and left mixture. I notified ZZZ center that I had an engine failure and asked for a block altitude and airport nearby. While they were giving me this I tuned off the left engine boost pump; left engine magnetos; left alternator; and pulled the left landing light breaker (tied to the left pump). I continued the descent where I picked up the weather; determined the ideal runway (RWY XX); and requested that the passengers to please buckle up. About 9 miles from the field I notified Center that I had the field in sight and they cleared me for the runway and frequency change. I continued my descent into a 4-5 miles right base where at 3 miles I put 10 degrees of flaps in. At 1.5-2 miles I lowered the gear and on short final before the threshold I added flaps 25. I touched down just past the 1000' markers and took the first taxiway to the left. From here I called center from the ground to notify that we had made it safely. After I called I continued taxiing to the ramp where I shut down. After we got out; we removed the cowling to find the crank shaft had a hole blown in it.