I had the hood of my bronco to install a fiberglass cowl scoop. I was able to get the hood back ontop of the motor bay by myself, but I wasnt able to bolt it on by myself, so it sat for 2-3 weeks with the back of the hood proped way up in the air, resting on the hood hinges. We had a few really bad rainstorms come through, and I didnt think to cover the front of the truck.
After I finally got someone over to bolt the hood back up, the starter wouldnt go and I had a dead battery, which all puzzled me. Replaced the battery and starter and at first it started to spin then seized up and wouldnt budge. I pulled out all the sparkplugs to see if it would turn over with no compression, and when I pulled the last plug (driver side near firewall) a whole bunch of water stared to drain out. Yeeks. So I fired up the starter and the motor turned fine, and for a few strokes blew a ton of water out a couple of the spark plug holes. I squirted a little oil in the plug holes, reinstalled the plugs, and fired it up. It started fine, so I quickly shut it down.
Then I went ahead and did an oil change (it was due anyways). As soon as a cracked open the plug water started draining out, then the oil. I put new oil in it and everythings ready to go, but before I drove it I wanted to see what you guys all thought. Anything else I should do here? Think its gonna be ok?
I was thinking because I have a large k&n open air filter that maybe the water just soaked through it and ran into the carb? I dont really see any other way the water could have gotten in. It was a downpour a few times, got really soaked. Thanks for any advice.

 

At the VERY LEAST start it and run it until it warms up completely -- idling, not driving -- shut her down and do another complete oil and filter change. At least that should purge the water from the lubrication system.

You might also pull your carburator and drain the fuel. There might be water there too.

After that -- all you can do is cross your fingers. If there's damage you'll not see it until you start hearing strange noises from deep in the block, or you start seeing serious blow-by. Hopefully there's no serious damage.

Hope this helps.

 

Make sure there is no more water above the rings. Water doesn't compress like air/fuel mixture so it is really hard on EVERYTHING. At least it isn't a diesel. A friend of mine's daughter drove her diesel through some deep water and some got pulled through the intake and it seized the engine (bent rod etc). With a gasser, you might be okay as there is less compression and less tolerance in the rings, but you really do want to make sure all water is out above the rings.
Keep an eye on the oil. If it gets milky after you run it for a short while, change it again.
Change your spark plugs, and dry up the distributer cap real well and keep fingures crossed.
Good Luck, Tim

 

I sunk the front of my 78 bronco in a river and hydrolocked the eng. Same thing as you. I pulled the plugs, drained the oil(into a pan) added fresh oil and drove it home. I then changed the oil again. Never had a problem. The biggest issue when you hydrolock an eng is bending a connecting rod. On the 351 or 400 you have, the rods are very strong. You will be fine.

 

put some sea-foam in your engine. This stuff will mix with the water and help it evaporate

 

This may be a dumb question but what the heck is sea-foam?

 

Thanks for all the advice everyone. I did open the drain plug again today and saw some water come out so I drained the oil again. Ran it for a few minutes after refilling, and I'll let it sit for a day or so and check the oil again. I was trying to think how the water got into the oil... and I remembered I also have an open element air breather on the back of the pass side valve cover. I hope I dont have this problem now everytime it rains! Would have though twice about the scoop.

I was lucky that the engine filled with water while it was off, therefore no bent rods. And there was enough water in the cyclinders to prevent the starter from cranking and wouldnt even turn over. Water sure doesnt compress easily, its funny to think that a rod would bend before some water would compress, but its the truth! lol