Anybody Ever Seen This Before?

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RustyRatRod

RustyRatRod

I was born on a Monday. Not last Monday.
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This is on my buddy's 71 Chevy truck I've been workin on. It's just a warmed up 350. He blew a head gasket on it and it sat for like 7 years. Local Chevy "guru" built it. He asked me one day while I was still at O'Reilly if I would look at it and see if it was worth fixin. I did and I fixed it. It ran really good. Finally got the brakes where we wanted them and we decided it was time for him to try to drive it some. Third day he was out and came back home, pulled into his parking spot, revved it once and it went POP and quit. Wouldn't restart. Now, I never touched the timing cover. All I did was remove the heads, had them worked, cleaned it all up, put an HV oil pump in because he wanted one and put it all back together. So I got the timing cover off today and here is the carnage. WTH? Cheap parts? I cannot believe the guy didn't put at least a double row chain set in it as cheap as Chevy parts are. I turned the crank by hand and cannot feel any contact with anything whatsoever. I can turn the camshaft, but it is difficult......it does still have all the rockers adjusted, so that accounts for that I believe. I've never seen a crank sprocket shear like that.
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Chineseium.... Like you mentioned Chevy parts are cheap why would you cut corners... Chevy "Guru" sounds more like a Chevy crook...

When you say "I turned the crank by hand and cannot feel any contact with anything whatsoever" I'm assuming you mean you feel no interference but it takes normal torque to rotate?

If you want to make sure it didn't bend valves pull the rockers & add compressed air.. If a valve is bent you'll hear it either through the carb or out the tailpipe...
 
Holy crap! The only thing I’ve ever seen do that is the nylon 318 camshaft sprocket. Never a crank sprocket.
 
Just noticed it broke the chain also. Wow
 
1WildRT said:
When you say "I turned the crank by hand and cannot feel any contact with anything whatsoever" I'm assuming you mean you feel no interference but it takes normal torque to rotate?
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Correct. I'm just going to install the new chain set and run a compression test. If any fail, off with the heads. Again. lol
 
I’m guessing the chain was really stretched and an extra link bunched up and got caught between the cam gear and the block. Stopping the cam in its tracks. Any signs of that happening?
 
High volume oil pump, stiff valve springs and cheap chain/sprocket set.
 
1WildRT said:
Chineseium.... Like you mentioned Chevy parts are cheap why would you cut corners... Chevy "Guru" sounds more like a Chevy crook...
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Yup, we've already figured that out with some follow up stuff I did the first time around. All the local Chevy yahoos in the big local club slobber all over the guy. It's sad, but Kitty summed it up. She said "he saw a black guy and figured he could rip him off" and that's the truth. But my friend Terius is the best guy ever. My brother from another mother. Best friend I ever had. He's a local police officer. It escapes me how somebody could have done him such a shitty job. It'll be right when I get done. Dammit all.
 
TT5.9mag said:
High volume oil pump, stiff valve springs and cheap chain/sprocket set.
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The valve springs are small diameter, but that's Chevy stuff. They are pretty stiff. I set the installed height correct myself.
 
RustyRatRod said:
I'm hoping that's all. The cam sprocket had some pretty good resistance, but it will turn.
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What I meant was that was the reason the chain was stretched. Stiff springs and hv oil pump. Read post 7
 
Here are both ends of the chain. What happened first? The sprocket give it up or the chain? Both?
IMG_20220527_210820[1].jpg
 
TT5.9mag said:
I’m guessing the chain was really stretched and an extra link bunched up and got caught between the cam gear and the block. Stopping the cam in its tracks. Any signs of that happening?
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No, but there was one crank sprocket tooth crammed in between two cam sprocket teeth under the chain. I was able to retrieve all the broken pieces out of the oil pan with a magnet too. I essentially reassembled the crank sprocket so I know I got them all.
 
That makes sense. So it broke a tooth and wedged it in there. I’m gonna guess it broke the chain after it broke the tooth. Then all hell broke loose.
 
TT5.9mag said:
That makes sense. So it broke a tooth and wedged it in there. I’m gonna guess it broke the chain after it broke the tooth. Then all hell broke loose.
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Hopefully, that's all we're lookin at. I'll know in a few days when the new chain set gets here. Got a Comp billet set coming. As easy as Chevy motors are to do, I'm completely appalled the guy did this. I see him all the time too.
 
We need a picture of the truck too. That's a nice series of truck IMHO.
 
Ron_M said:
We need a picture of the truck too. That's a nice series of truck IMHO.
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I'll get one tomorrow. It's done got dark now. It's a 71 short bed step side. It's a cool truck, but like most all but the best restored, it has rust. It's completely savable, though. It's got a Borg Warner Super T10 4 speed, too. lol
 
Another possibility in today's world of "QC" is maybe "mixed parts." Maybe the chain or one sprocket was just a BIT off ***** and bound up, causing the break
 
67Dart273 said:
Another possibility in today's world of "QC" is maybe "mixed parts." Maybe the chain or one sprocket was just a BIT off ***** and bound up, causing the break
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That's a good thought. The engine, even though it sat for about seven years only has about 500 miles on it. I wouldn't think it was that the chain was stretched from being worn out. Something definitely happened.
 
Chain had to let go fairly late in all that carnage. If the chain broke first the crank sprocket wouldn’t have shed all its teeth. The crank sprocket spinning against the chain that wasn’t spinning (or wasn’t spinning fast enough) stripped the teeth.

If the chain was just really loose, like mismatched parts, it could have skipped when he revved the engine. I’d make sure I checked the cam and valve train really well too though, because the other possibility is that there was too much resistance from the cam gear for the crank sprocket teeth. Which could mean the problem started on the top end.
 
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