Got a timing belt job turned into a nightmare last Tuesday in Denver

Customer brought in a 2010 Honda Accord for a simple timing belt swap. I lined everything up perfect, triple checked the marks. Cranked it over by hand and the pistons hit the valves. Turns out the previous shop had the cam sprocket key sheared and it was running out of time anyway. Had to explain to the guy he needed a whole new head. Has anyone else seen cam keys fail like that on these J35 engines?

2 comments

2 Comments

val_williams1mo ago

Whole head seems extreme for a sheared key. Sure it wasn't just a jumped tooth?

phoenixb341mo ago

2008 J35 with the same problem up in Boulder last fall. @val_williams I get why you'd think it was a jumped tooth but those keys can actually crack from heat cycling over time, especially if the motor ever ran hot. I had one where the key was just barely holding on, looked fine from the outside but the sprocket was walking a tiny bit every time it ran. By the time you get the head off and see the valve damage it's usually cheaper to just swap the whole thing than trust a used head that might have the same issue down the road.