Valve reliefs in the pistons does not mean that it is a non interference engine. The valve reliefs may only provide clearance for the valve overlap at the top of the exhaust stroke. If the belt breaks, then the valves get out of sync and if a valve is fully open at the same time the piston is at TDC, they collide.
My question to the OP is did you actually see a credible source that says that the pistons and valves will never touch or are you just assuming this because of the shape of the pistons.
I think the picture that @texases posted was a good idea.
I agree with him. Those valve reliefs imply absolutely NOTHING about whether an engine is interference or not. In fact, those valve reliefs were very common on chain driven OHV V8s, which were around LONG before timing belts and the term interference engine even existed.
Did you know that the Ford 5.0 liter (302 cid) is an interference engine?
A friend was on a return hunting trip in their Ford pickup when the timing chain let loose. The plastic teeth on the cam sprocket came apart. They had it towed to a local town to have the chain replaced. The shop called them the next day and said they installed the new timing chain but the engine had no compression. So instead of paying those shop rates they trailered the truck to my shop. When I removed the heads every exhaust valve was bent.
My “source” was someone making a comment on a discussion forum similar to this one. Not knowing much about engines, it’s kind of hard for me to tell truth from bulls**t.
Well, okay then. I’ll go ahead and replace the belt.
@Tester: Sure, the old 302 was an interference engine. So were lots of Cadillacs, and I’ve seen a Chevy 350 bend valves when the cam sprocket blew banging along the freeway at 75mph. Currently most, if not all, Ford chain driven engines are interference engines. People gripe about timing belts, but talk to the guy with the V-6 Explorer that needs $4000 of cylinder heads because a timing chain cassette blew up.
Our family fleet includes a 2001 Civic LX sedan, 1.7L SOHC, 5-speed manual. I have the Haynes manual for this car, and in the section regarding checking the operation of the engine after a timing belt replacement, it states on page 2A-13, line 29, “Slowly turn the crankshaft counterclockwise two revolutions and recheck the timing marks and camshaft sprocket index marks for proper alignment. CAUTION: If the crankshaft binds or seems to hit something, do not force it, AS THE VALVES MAY BE HITTING THE PISTONS, if this happens, valve timing is incorrect. Remove the belt and repeat the installation procedure, then verify that the installation is correct.”
I’m only a shade-tree mechanic doing routine maintenance on our cars, but to me this seems like if the belt is not turning the camshaft/valves, they are going to hit the pistons.
We recently had this belt replaced on the Civic, and the water pump, tensioners, all three belts (timing, alternator, A/C, and a camshaft seal that was leaking oil were all changed for <$700 at a local shop. Based on th Haynes description, this was a pretty good deal considering how much has to be disassembled to even reach the belt to pull it off. I did this job on my '79 Scirroco back in the day, but I wouldn’t try it on my own on this car.
At 160,000 miles, you are way past due on time and mileage and living on borrowed time. It could go another 20,000 miles, or lunch the head or worse, so I’d highly recommend doing this service ASAP.