Why did your timing chain break?

[4jrfox]

Why does a timing chain break and what dammage did it cause and how did you fix your explorer 5.0? My timing chain broke on a 10,000 mile new old motor. On idle my truck came to a halt. I couldnt get it running! found out the roter wasnt turning and the timing chain was in the bottom of the oil pan. Pulled the valve covers off and I had bent valves and push rods. I had a total rebuild all new valves new harden push rods new springs valve guides everything new even a new doubble roller chain. Put it all back together started right up for 2 minutes than heavy valve noise again. Bent the valves in the #4 piston and push rods. Im really depressed because of all of money I spent. Here is what I have:
1997 gt40p iron heads, ported polished small charger comp cam 512 lift. Ford roller rockers, stainless valves harden push rods with new springs. BBK SSI intake with a 9 pound powerdyne charger. Before I done the initial problem there was 3,000miles on this setup.(except the charger is new). The only thing I can thing is the valve adjustment is a tad complex on the ford rollers preload. Im thinking this is what it could be. Im a good mechanic and this p me off! Any one in the Houston area has experience with the adjustment and want to make some $ on a Sat or Sunday let me know. Im afraid to start again.

 

[CDW6212R]

I'm sorry to hear of your problems. Unfortunately many times a failure like that can be traced to a valvetrain that wasn't set up correctly. I'm not jumping straight to that conclusion, but it is the most likely cause.

Jake referred me here, so I'm being more thorough with my answer. I'm not picking on you, but trying to be generally accurate in describing most engine builds by non pro engine builders.

It is critical for any new combination of valvetrain parts to check them all, confirm that they are all compatible, and to double check all dimensions. That description of assembly sounds easy enough, but it is actually not at all easy or simple.

The fact is that most people accept recommendations from advertisers as to parts compatibility. They then assume everything should work great, and they start bolting things together. Unfortunately most people skip critical checks. The result is not a failure each time, it's amazing that far more people don't have serious issues.

Just because an engine runs and doesn't "blow up", that doesn't mean that the parts are all perfectly matched and will be great for 200k miles.

It is critical to check the piston to valve clearances, and the camshaft specs(degree it), the pushrod lengths and rocker arm geometry. If the parts are all stock then of course it should bolt together. But most people change something in the valvetrain, and each time those checks must be done again.

Setting the lifter preload(hydraulic) is simply the last final bolted down part. The process of checking all of the critical components doesn't begin there. That stuff must be done before the final lifter preload is set.



4jrfox, give us more details of the valvetrain. The pushrod V8 may seem like a really simple design, but it still has to be right to survive and make good power.

My first thought of the few details here is that the cam shouldn't have been used. There is no place for an expensive off the shelf camshaft in a nice supercharged engine. For all of that money spent, the cam should be a custom cam made specifically for that vehicle combination. The valve springs should be exactly as instructed by the cam designer, not read from a book/chart. Tons of horsepower and reliability are lost using OTS cams. The makers of those cams do not have your best interest in mind. They just want to make a bunch of cams and springs which they can talk you into buying, no matter what vehicle you have. Regards,