350 spit out cam, any ideas why?

[Rifter_Chevy]

So my engine went boom a few weeks ago and im just throwing around possible causes in my head and want to hear options, doesnt really matter but should be some fun discussion.

It was a 350(mostly), it was not taken care of by previous owner, when i bought it it didnt even have a oil dipstick and had less than 3 liters of oil in it and was leaking oil from every possible spot it could leak oil from so i guess it ran in a state of oil starvation for most of its recent life till i got a hold of it. I drove it for a year till it went boom.

It had a 305 head on one side and a 350 head on the other(didnt notice this till i pulled it after it died), was a 350 block 4 bolt main.

I was driving on the highway and noticed a lack of power, like a huge lack of power i couldnt maintain 40mph up this hill i can usually do 65mph on without even trying. As i started to pull over engine stalled and locked up solid had to put it in neutral to roll off the highway. Puked out a very small amount of oil that was pitch black and water like(oil level/condidtion was good as of 3 days prior when i checked it last). There was no oil in it and was blowing plumes of white smoke out of the valve cover breaters and the oil dipstick tube when i pulled it out.

So I pull the engine and fine out that the cam snapped in half between the 7,8 and 5,6 cylinders. And then spit the cam out of the block into the flywheel really messing up the tourque converter bolts and making them really fun to remove.

The rocker studs on 7 and 8 were snapped off, 3 pushrods bent and one gone, never found it. One lifter was also gone and i never found it either. TONS of metal shavings in intake valley, probably the missing lifter and pushrod remains but the largest piece of metal shaving was the size of a uncooked grain of rice.

So what do you guys think would cause a cam to blow out the back of a block?

[BigBlocksRule]

Once a cam breaks, all bets are off. You had pieces of cam that weren't turning but still probably had valves lifted. Once a piston smacks one, the rest of the valve train passes that motion along to the valve train. Something got wedged in just right to transfer that motion toward the rear of the block.
If you're going to keep the block, make sure to have it thoroughly checked. I've seen a few cracked in the cam tunnel from your type of catastrophic failure.
Next time, go roller!

[ctandc]

Sounds like oil starvation finally caused the cam to give up the ghost. Honestly it could have been a combination of several different things from the way you describe the condition of the engine when you started messing with it.

[sean1969c10]

350's aren't that hard to find, I would find another block to start with. After years of abuse the cam bores could be out of alignment now and the machine work to correct this is hardly worth it on a stock block. Just my .02c

[Weasel Diesel]

Don't forget in a Small block that the first stop on the oil circuit is the cam bearing. If those go, then everything starves.

[ctandc]

Look for a later model, 1 piece rear main seal 350. '89 and up truck motor would be ideal. Throw on a set of Vortec heads, a small roller cam, and have fun.

[raceman6135]

I had an engine failure somewhat similar to OP's.

What happened was that a connecting rod bearing spun, which overheated the rod and it broke. The flailing part of the con rod that was still attached to the crankshaft swung up and broke the camshaft into 4 pieces. The rear-most piece pushed the cup plug out the back of the block into the flexplate, stopping the engine from rotating.

If the OP checks the connecting rods and finds one or a pair of bearings hammered to dust, I'd bet the same thing happened to him: rod contacted cam, cam broke, domino effect.

[Weasel Diesel]

Originally Posted by raceman6135

What happened was that a connecting rod bearing spun, which overheated the rod and it broke. The flailing part of the con rod that was still attached to the crankshaft swung up and broke the camshaft into 4 pieces. The rear-most piece pushed the cup plug out the back of the block into the flexplate, stopping the engine from rotating.

That is a severely good theory... and darn sure plausable.