Hi all, I know this isn't a thirdgen question, but with all the knowlege you guys have regarding SBC's, I figure it couldn't hurt to throw this out there. I apologize in advance for the length.

My brother has a 1973 Corvette Stingray, 350/4sp with @71k original miles. The last time he drove it, about three years ago, it just quit on him and wouldn't start back up. My cousin, who's mechanic skills are questionable at best, insisted it was a blown head-gasket. I doubted that from the start since that wouldn't just make a car quit an not start.
Against my advice, my bro lets my cousin work on the car. He gets as far as removing the valve covers and intake, and upon noticing a broken valve spring and two broken pushrods, my bro makes him quit since its obviously not a blown head gasket.
To make a long story short, the #3 exhaust valve spring broke, dropping the valve and breaking two pushrods.
I think the engine needs to come out for complete overhaul. My cousin still insists otherwise, and my brother is hesitant to pull the motor in an effort to maintain the originality of the car.
My question is this: What other carnage can occur due to a dropped valve? I'm heading over to my bro's house one night this week (hopefully tonight) to pull the heads and check on the pistons and cylinder walls, but I fear a possible bent connecting rod.
Let me know what y'all think!
Dave

 

Earlier this year I tore one down that had dropped a valve. I stopped when I saw the spiderweb of cracks in the cylinder bore. On that one it junked the block and cylinder head on that side.

 

See, that's exactly what I'm afraid of finding. I keep telling my bro that there is bound to be more problems, and now is a prime time to pull it out and rebuild it. My cousin, a bodyman by trade, is a decent mechanic, at least for basic stuff, but his abilities are limited when it comes to things like this. Not that I'm a master or anything, but he seems to lack a little common sense.

Thanks for the response! Anyone have an experience they're willing to share? I'm going over there tomorrow to remove the head and see whats up. I hope its salvagable!

Dave

 

Did the valve drop completely into the cylinder, or just drop down a little? You could have minor valve damage, to guide damage, to head damage, or piston/rod like you suspect, or broken block as already stated.

The only way to know is to pull it apart. Most of the stuff mentioned can be repaired on his "original" block. A broken cylinder can be sleeved, most head problems can be machined/welded, etc. Replacing valves, guides, and springs are all pretty standard machine shop operations.

 

Honestly, I can't remember how far the valve dropped into the cylinder. It broke down about three years ago, sat for a while, and then my cousin went and worked on it, and its sat some more. I've only looked at it once, and I remember seeing one broken valve spring, with the retainer and clips sitting there on the head, one pushrod was broken in two places, and I can't remember if a second was also broken or bent. We have not pulled the head yet to check out piston and cylinder. I know the damage could be minor to catastrophic, and obviously I'm hoping for the best for my bro's sake.
I still feel its time to pull the engine out and rebuid it. It was smoking a little anyway last time it was running (pretty sure it was just valvle guides though).
Thanks for the help, guys. I'm going over to my bro's house tomorrow to pull the head off, I'll try to bring my camera and take some pics of the carnage!

Dave

 

I wouldn't take any chance and TEAR IT DOWN. Metal shavings on top of all the previous problems could exist causing bearing failure or worse. That car/engine has just about every part available to keep it 100% correct so don't let that be the deciding factor. Most likely if you just fix the visually obvious problem, many problems will follow down the road, do it right the first time.

 

Allright, well, I was over at my bro's house last night working on his 'Vette. We finally got the driver's side head off and it was the worst possible case scenario. The #3 exhaust valve broke, bent the #3 intake valve pretty bad, cracked the head, put a couple holes in the combustion chamber. So the head was junk.
Then we saw what was left of the piston. Two holes in the piston and it was broken into about a dozen pieces. Got all that crap out and the block was wasted too, along with the wrist pin and that connecting rod. The engine is still in the car, where it will remain until my brother can afford a completely new engine.
You hate to see this, but I couldn't help getting at least one pic to share w/ you guys. Sorry its a crappy cell-phone pic.

dave

 

You absolutely sure the block is junk, can it be bored to clean up? You mentioned in another post about how your brother was concerned with a numbers matching car, if you change the block, it will not be numbers matching and devalue the car significantly, especially since it's a Corvette (found this out the hard way years ago). You can change everything else and keep the current block and have it machined would be the optimal choice, if not do your best bet is to find a good block with the same casting numbers for originality.

 

Well, That's done....My advise, take the engine out of the car, get what you can sell or use off the engine and build a new one. Fact is, that engine is going to cost you a lot more time and money to repair then the ADDED re-sell value of the car will bring with the correct casting numbers. In other words, an old car with a new engine..worth $$,$$$ Minus your cost to replace.An old car with a totally rebuilt engine...worth. $$,$$$, Minus your cost to re build. And honestly, if your planning on keeping the car, racing it, you'll better off. I know the numbers the numbers. Always buy new parts you'll be money ahead in the long run.

 

Oh, the block is destroyed, that cylinder was shattered almost as bad as the piston. Didn't even find all the parts of the cylinder wall, I think some chunks went down into the oil pan.
I know he wants to keep the car, he's dreamed of owning a Stingray since he was a kid. Racing it, no. This car is pristine except for the engine, very nicely kept survivor with 71k original miles.
He just had a baby, so money is tight right now. We were talking last night and think he's gonna look for like a junkyard motor for now just so he can drive the car, then as time and money allow look for a good block with the correct casting numbers to get the car back to original.

 

Put in a used motor 'til he has the money to do over. I wouldn't let go of a car I dreamed of owning for such a long time. Things turn out better when you're not in a rush to get it done, he's waited this long, a couple more years should be a breeze.