Factual error: While handling the ignition coil cable to the distributor cap, Joe Pesci tells De Niro that the timing chain needs adjustment in his truck. A truck of that year with an inline Chevy motor would not have a timing chain at all, instead this truck would be equipped with a direct drive timing gear. Even if it had a timing chain, it would be behind the water pump and a cover. It would have been a several hour job to replace, not possible to adjust it.
Continuity mistake: When Elton and John Reid are kissing in the cupboard John's hand keeps changing between shots. John's hand rolls down Elton's chest, then the next shot it's on Elton's cheek, the next shot he takes his hand away, then the next shot his hand is by Elton's mouth and Elton pretends to bite John's thumb.
Continuity mistake: After Mick Mars has Nikki and Tommy kick the guy out with the guitar at his audition, the guy leaves and cries through the door. Nikki is standing by the door and looking nearly straight forward as the guy leaves, but then the camera changes angles and suddenly he's looking more to the side towards the door. Also his arms are a little higher up holding his guitar.Quantom X