Well, as they say, nothing lasts forever. The weather was nice on the 4th and I decided to get the car back out. I swapped my home brew carbs on the night before. I got it running and checked a few things over and took it out for a drive. Cruising around felt pretty decent. Made a few scenic trips to put some miles on. Everything seemed okay. I figured it was about time for a performance evaluation. I headed over to a local test spot(in Mexico) and tried to make a hit. I let the clutch fly at about 6200 and ran in through 2nd and 3rd shifting between 78-8000 and ran it halfway through 4th. Seemed very strong. Came up to the stop sign and took a left and jumped on it a little more, when all the sudden......Smoke rolling from the valve covers(hood is still off). Hmmm. Thought maybe a gasket or something started throwing some oil? Then I hear a faint tapping sound. Nah, can't be. Well, I make it to the next turn and the tap turns into a knock. I look down at the oil press. gauge and it's not happy with me. Sinking like a lead balloon. Uh oh. I'm only 1/2 mi. from home. Tried to go real easy, but the knock was loud and it felt like it was losing power. I shut it off and pulled over. I called a friend from down the street for a tow home. Looked around on the engine and nothing out of place, everything is dry. Get it pushed back in the garage and let it cool off. Pull the valve covers and see this:
A little milky.....
Then I check the radiator and it's down some. Great. Figure I might as well cut the filter. As soon as I pull the filter I'm greeted with this
Cut it open to find plenty more where that came from.
So, I blew it off and worked on something else the next day. Grabbed my borescope and coolant pressure tester from work and checked it out more last Fri. I pulled all the plugs. Nothing too obvious. Started looking in cylinders and got to #7. Huh, looks like a small puddle at the bottom of the cylinder. I pressurize the water and it starts filling up fast!
https://m.youtube.com/shorts/Vk5vpvK7cUcOn the left side of the screen, you can kind of make out the valve reliefs on the piston. And a bunch of water on the right! Half the piston is submerged. I figured it better come apart so things don't get rusted inside. Pulled the engine out yesterday and got started on the autopsy. Once I got the head off, I found the obvious cause:
The knock:
The cylinder has a pretty long crack.
The big end on #7 rod is pretty ugly. Don't think it can be re-sized, so prolly need a new one. Luckily the damage was very isolated. Every other journal looks like it never ran, like I just assembled it. I think the coating on the bearings and a good oil additive helped me out. Looks like the crank can be turned on just the rods. Cam still looks like chrome from polishing. Can barely see where the lifters were riding.
Crank still nice and shiny.
Haven't gotten the oil pump apart yet, but hoping the aluminum bearings did minimal damage. I guess it could have been a lot worse. It was a one hit wonder. Butt dyno said it was making every bit of the 335hp factory rating when it let go.