A friend has a small block chevy (late '70's).  His son was "just driving along" and "it blew out a big cloud of white smoke and made a rattling sound". Upon further inspection it was determined that the oil pan was full of water. I do not believe a blown head gasket on a chevy V8 will allow the oil pan to fill with water, I think that the block has to be damaged.  What do guys think?

Your friend has a cracked block, time for a rebuild !!

Usually it is a head gasket and not the block. It could also be the head cylinder also. See if there is oil in the radiator. Take the plugs out see if any are wet wit Anti freeze. Do a compression test. Then have a Cylinder leak down test done. I suspect it is not the block  unless it was reved real high.

Heads have water passages also, maybe they are cracked. It is less likely than the block but still possible. Unless you throw a rod and it punctures the block, blocks are pretty tuff, heads will crack first if it a failure from abuse (warp, cracking). HOWEVER, blocks can be easily damaged/destroyed by water that freezes in water passages, expanding and cracking the block. This is more rare though since most people remember to put in anti-freeze.

BrenLover

My guess would be the head or head gasket.

....me too!

I go along with these guy that I'd suspect either the head or head gasket.  The rattling sound worries me. Sounds like posibly rod or main bearings.

JFP! Are you coming????

I haven't heard back from you!!!!

Eric The(LeavingSoon)Hun[>]:)]

I've done maybe a dozen headgaskets on SBCs.  Almost all had oil that resembled a milkshake.  Sometimes they blow the opposite direction and you get exhaust gases in the coolant but most times it's between the water jackets and oil passages.

Eddie

E-T-H,
I e-mailed you last night but there was a problem with my computer and I do not know if it went out.  I am at work right now with no e-mail access...............

The "rattling" makes it sound VERY serious!!  Time for a rebuild I suspect.  Antifreeze attacks bearings rapidly so they need inspected.  Best plan is pull the engine, disassemble enough to find leak and check the bearings.  Decide from there where to go.  Small blocks are easy to work on and reasonable in cost for parts.  Avoid rebuilder engines from various sources such as AutoZone and the like.  They are nearly ALL crap!

If the car is a collector item you need to keep original castings anyway to maintain value.

My brother blew a head gasket on a 924 Porsche.  The gasket failed between the number 3 and 4 cylinders so that the compression gas and air from one cylinder was force into the adjoining cylinder. It made so much moise I thought it was much worse that it was.    

HEY!  Beekeeper of little faith!  These mysterious breakdowns happen all the time, especially to young men driving their parents car.  

Science hasn't yet figured out WHY the parents will drive a car for decades, but soon as a young fella hops in and idles on down the road a bit, all the metal fatigue (from before he started driving) in one part or another seems to be aggravated from the too-slow operation by the relative novice.

They think years of wear and tear by Mom and Pop caused various parts of the car to be hanging together by mere threads of metal, but they haven't been able to prove it.

Even more puzzling is why only certain areas are affected.  

While transmissions, head gaskets, u-joints, rear leaf springs, mufflers, connecting rods, valves, head gaskets, pistons, clutches, rear axles, etc. very often experience this harmonic acceleration of the failure cycle, other parts such as steering and front suspension & front tires, hinges, turn signals, and so on, seem unaffected by this mysterious premature breakage.

Not just metal parts, either.  For some reason, the back tires, especially on the passenger side, seem to deteriorate and wear out rather quickly.

Oddly, once a failure occurs -- say to the clutch, something must happen to the neghboring parts, which then puts extreme angular loads (or other phenomena) on the replacement parts, because often that new clutch will itself be toast in a week or two.

If I hear any more about this mysterious process, I'll let you all know, having been a victim myself.  Why once as a teen, I was just driving along when a pivot bracket for the column-shift linkage popped right off the frame and I had to limp home to my folks in first gear.

Equally odd was the was the ignition cut out as I was slowing down from 45mph and then came alive again after I'd pumped the gas (trying to get it going).  The remarkably small backfire caused a small hole in the muffler of the station wagon, which grew and grew until I arrived home when it was quite large.

Anyway the main concern should NOT be the head gasket on the ENGINE.  I'd worry more about the head gasket on the Old Man.

What's all this BS hinting that the son is at fault here?

Next thing, you're gonna say that young bucks actually will not volunteer all the facts when they have to break some bad news to their fathers [;)]

Update.
First all the history,
The  engine was a basic rebuild for for a "hot-rod" pick-up truck built by a guy I work with. Four months ago he sold the truck to another guy we work with for this guys 16 year old son to drive to school. Sixteen years old kid proceeds to have "reving" contest with his buddies to see who has the loudest pipes, which he usually wins.
Jump to thusrday afternoon,  the kid is just driving along,  (drag racing) over revs the engine (which does not take much because of the fact that it was not built to race).  Well right about this time the #6 piston lets go rippig a good size hole in the block. This is when the proverbial "puff of white smoke"  was seen exiting the exhaust of said vehicle.

Son will now be getting a job.................