So a friend of mine had his timing belt snap on him the other day at ~5000 rpm in a stock '90 Si motor. We all assumed the thing was messed up and with the understanding that we're going to junk the whole car, we took the head off just for ***** and giggles.

We totally half assed it, we didn't drain the coolant and oil, we scratched up the block while trying to pry the head off, etc.

We finally look at the valves.... everything was perfect. Zero damage. Never having taken a motor apart, we slapped a Pep Boys head gasket (scratched while putting it on) and timing belt on with out even taking off old gasket material, and now the thing runs perfectly.

I always understood that a timing belt snap on this motor would destroy it. I refuse to believe that simply luck kept the valves from getting bent to hell at 5000+ rpm. Anyone know what's the story? Have we all been lied to all this time? Is there a fail-safe that keeps valves from hitting the pistons when the belt breaks?

 

Since (most?) honda engines are interference engines, (meaning that the valves and pistons can contact if moved at the wrong time), I would guess, much against your wishes, that luck was on your side. I had the timing belt snap on my old D16A6, and I didn't even bother checking it, because I knew it was garbage. That and the motor was constantly breaking down. You're right though, at 5000rpm, that sounds odd that there was no damage at all... As far as I know, there is no failsafe incorporated in these engines... I think you just had some dumb luck there, man

 

Your lucky. God was looking after yall......errrr your motor .

 

There is no failsafe but on motors with lower compressions the valves are less likely to contact the pistons. The higher the compression the more likely the pistons will contact due to the raised piston height.