My question pertains to a 1994 Accord EX 4 cylinder engine.

If the valves get bent when the timing belt breaks while the engine is running, what is the likelyhood that there is also damage to the pistons? I'm asking because I want to know whether I should go forward with repair or not.

Thanks in advance!

 

From the threads I have seen posted in the past regarding a broken/stripped belt and bent valves the usual outcome when repairing the head was the engine ran fine after.
I cannot say there has never been a punched piston, but I don't think I've ever read about anyone needing to replace pistons. Just valves in the head.

 

You'll know once you remove the head!

Or if you are paying a shop/someone to do all the work, have them scope the cylinders prior to the tear down. I would assume that most garages should have access to a cheap video scope these days. I bought one for $150 with LED lights that works great.

 

I agree with GhostAccord, remove the spark plugs and a scope will let you see the condition of the piston when rotating the engine (piston comes up to top) Scopes are very cheap on amazon.

 

You are going to need to pull the head so normally you can just pull the head and check then, but like everyone is saying, normally you aren't going to have piston damage, the pistons are much stronger than those tiny valves that will just bend out of the way.

A timing belt breaking is much better than a head gasket failing and the head warping. Just have a machine shop swap out whichever valves are bad and after reseating it will be fine. They may ask to resurface the head but it's not needed at all, just have em check it for straightness but the surface will still be straight.

After slapping the head back on, be sure to run a compression test before putting anything else back together just to be sure all is well but they should do a pressure test to be sure the head is in good working order they they replace the valves and before handing it back to you.