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Q: A loud noise is coming from my engine

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it sounds like a bolt inside the engine, it is a very random noise not a constant timed sound, the transmission is a t56, and the flywheel was just replace with all new bolts. the pilot bearing was also just replaced, the engine just had a new cam, and new springs put in, i took the valve covers off and ran the engine and everything looks fine, i took the intake manifold off and the valves all look good from what i can tell. it sounds like a broken connecting rod, but the rods looked good when i took the oil pan off, and the engine has not been revved over 2500 since being in the car, just idled to move the car. so i don't see how the rod could have broke. i will have to pull the engine to check the bottom end so just wanted to see if anyone had any ideas. the noise is very loud and i don't want to run the motor and cause more damage. i also checked the starter and it seems like it is working properly not staying open and hitting the flex plate. i am at a lose at this poin

Hello - You don’t mention what make, model, or engine we are discussing, but with a T56 behind it, we’ll assume it is a V8 of significant size. There are many possibilities given the recent engine work, and your thoughts about connecting rod or main bearing problems are good guesses. Other possibilities, depending on the engine design, could include a loose oil windage tray, cam timing chain, tensioner, or variable-valve timing actuator, or a broken lifter or cam-follower, among other things. The possibility of a loose nut or bolt falling into the engine during the recent work is yet another nightmare to consider. I believe you are correct, the engine will need to be removed and torn down or at least have the pan removed to allow access so you can look for debris. If you would like some professional assistance with this, consider contacting a certified technician, such as one from YourMechanic, to take look and diagnose the noise. Good luck!

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