Originally posted by tbucketdom
I have Just installed my freshly built 396 in my T-bucket and got things going.My concern is blue smoke on overun.The motor was filled with a regular grade oil and run for 20mins at 2000rpm in the driveway and then driven normally(hard) for approximately 100 miles (short trips).I find now that under load or just revving the engine or even at idle their is no smoke but when you rev the engine and then back off it smokes blue. Is this due to the moly rings simply not being bedded in yet or is it something more serious?
A couple of things to check. Possible internal intake manifold gasket leak. PCV sucking a small amount of oil when backing off. Valve guide seals leaking slightly. Bad diaphram in the vacuum modulator (if automatic trans) allowing trans fluid to be sucked into the intake from the vacuum line.
A suggestion for you: Change your oil and filter. You don't mention doing that after the cam break in. It should have been done at that time and again after that first 100 miles or so.