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Timing chain broke, engine is ruined :( pics and video
What a sad day this is. I was on my way to do some 4th of July drag racing and while passing a van on a 2 lane highway, the engine completely died. It sounded and felt just like the rumble strip, with a large puff of blue smoke in the rear view mirror. In the video it's pretty difficult to hear but if you listen closely there is the noise from the rumble strip and then immediately the noise from the engine taking a dump, then the rumble strip again as I coast back across. I pulled over and called AAA. I tried starting it and got the signature low compression starter pitch. At this point I suspected a hole somewhere or the timing chain broke and the valves are open. Checking under the hood, the only thing I noticed was mild oil splatter around the front of the engine, no gushing, everything else looked okay. Now I'm thinking timing chain.
Well today I finished pulling the timing cover and my guess was correct. The timing chain snapped, punching a hole in the timing cover. The rumble strip noise and feeling was probably the valves and pistons getting beat to hell. Still haven't pulled the heads. Surprised the chain broke because the engine only has 60,000 miles on it.
In the middle of the tear down with hoses and crank balancer out of the way.
Water pump, cam sensor, and crank hub removed giving the first clear look at the timing cover. I was removing the bolts when I noticed the huge crack on the left.
Close up of the crack.
Close up of the pieces and the bolt that broke in half.
Wow you're right, hard to tell as it blends in and happens almost right as you're going over rumble strips.. That really sucks man, hope its not too bad and you can get her buttoned back up and on the road in no time.
They gave you what looks to be a stock standard non-roller chain, which seems weird considering the load on your valvetrain is heavier due to higher pressure springs. A true roller is a stronger chain, less friction, same style as a bike chain, etc.... if you have a mechanical w/p then go with this: https://www.hawksmotorsports.com/clo...ing-chain-set/
I'm trying to get the valves out but when I use my spring compressor tool the valves just go right down with it. I tried smacking them all with a rubber mallet but no dice. The only thing I can think to do is put the heads back on with like 5 bolts snugged down and use the tool to press the valves onto the pistons to get them to break free.
I just had a thought. My heads are Lloyd Elliot 21 degree Trick Flows. With increased PTV clearance, is it possible I dodged a bullet? Or is it still guaranteed some valves are smashed?
I take it the heads are off? Have you looked at the pistons? If there was contact made it should be obvious. You can try to use a socket and smack the retainer with the valve and keepers inside the socket to see if that will jar it loose. You can also fill the combustion chambers with mineral spirits or the like to see if they leak.
Not saying you're out of the woods, but I had a friend whose timing chain broke on a stock engine and he was able to get away with replacing the chain and the engine was just fine until he blew out the ring lands on a 150 shot.
I take it the heads are off? Have you looked at the pistons? If there was contact made it should be obvious. You can try to use a socket and smack the retainer with the valve and keepers inside the socket to see if that will jar it loose. You can also fill the combustion chambers with mineral spirits or the like to see if they leak.
Not saying you're out of the woods, but I had a friend whose timing chain broke on a stock engine and he was able to get away with replacing the chain and the engine was just fine until he blew out the ring lands on a 150 shot.
Drivers side head is off. Pistons look unscathed. They're forged though if that makes a difference. I'll try the 'ol socket smash thanks!
So the non-carbon spots on the valve reliefs on #'s 1 and 5 aren't from contact? If there are no sharp ridges or divots on any of the pistons I'd do the right thing, ensure the valves aren't leaking, put it back together with a roller chain and send it.
Disclaimer- by "the right thing" that's what I would do. Not saying that is the actual right thing to do...
#1 definately made contact with the intake valve. I would check both the valve and pushrod. No idea why someone would use that junk chain. GM does not sell their LT4 single roller but Cloyes still offers it. I run the single roller in my 383 Vortec. Mine is the SBC roller cam version but they offer the same design for a LT1/LT4 with the water pump drive gear.
Here's some bendy action for ya. I had to use a hammer and chisel on #2 intake on the combustion chamber side to get it straight enough to finally pull it out. Yeesh
What's your plan of attack from here?
For starters, unless it was an option which was overlooked, I'd tell Golen to get fucked for installing a stock chain.
Just checked the brochure and he does list it as "stock gm timing set". I wasn't familiar with how weak and inadequate it was otherwise I would've changed it when I did the cam swap.
This engine would need a new chain, oil pan gasket, heads need to be reworked and maybe a few other things. At this point it's not worth it to me, I'm going to do an LS3 swap. Kinda sad because everything I know about engines I learned from this LT1 and this forum.
I emailed Golen saying something along the line of how surprising and disappointing it was that the chain broke after 60k, he commented on how bad the break looked haha.
I'm going to post my whole engine and anything LT1 for sale once I get the short block out, have to buy and engine stand and hoist. Really sucks cause I was looking forward to putting some serious miles on it this summer.
I wasn't familiar with how weak and inadequate it was otherwise I would've changed it when I did the cam swap.
You know, waaaay back in the day a stock chain would have probably been able to handle this, but these days with the quality of materials the way they are.........................................
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Timing chain broke, engine is ruined :( pics and video 
