Thread: 400 SBC Rod Bearing Failure

Tweet

Oil pressure sounds great.

4 degrees is, I think, the recommended static timing for a SBC. Most guys will dial in a little more (10-12) to improve throttle response, then limit the total advance to somewhere around 34-36 degrees.

I would pay particular attention to TyphoonZR's post about total timing. If you were not the person who built the motor and have no idea about the squish distance (piston to head clearance at TDC), then stay on the conservative side of total ignition advance to prevent the motor from detonating and knocking the bearings out again. With a tight squish (0.035" to 0.040"), you can run a full load of ignition timing on pump gas.

Well, I have a bit over 20 hours on this engine now. I have changed oil on it a couple of times, and been very careful breaking it in.
The idle is set at 650 RPM, and runs at that warm (about 175 F). On initial start up cold, the oil pressure still goes to about 50 -55 PSI @ 900RPM, and about 65 - 70 PSI @ 1500 RPM. The oil pressure at idle (650) now runs about 15 - 18 PSI after a run at cruising speed. After running slowly for a while, it recovers slightly. Oil pressure recovers to about 25 PSI at 1000 RPM, and at 3500 RPM, I am running about 55-60 PSI after it is hot and has been running for a half hour or so. This has been consistent. I have been running Mercruiser 25W 40 oil (after the initial break in period).
It appears that opening up the clearances was the trick. Thansk to all who contributed ideas and advice.