Infrequent Coolant changes causing Electrolysis
This is an FYI to folks who haven't changed coolant regularly. I bought my 69 L71 coupe 2 years ago and almost immediately began restoration. The motor was put on a shelf intact. The previous owner installed a LS6 intake 20 years ago and put the tri-power set up on the shelf (which I recieved when I bought the car). Although I only drove the car a few miles before beginning tear down it ran cool. Last week my brother tore off the old intake and called me immediately saying you have to see this (see attachment). I'm a boater and recognized the elctrolysis you see in the attchment immediately. When we dug the crud out of the intake the walls had thinned by about 25% or more. Fortunately this is not the one we are going to use and heads/block are fine as the aluminum was the sacrificial metal. but I thought I'd share with you all this warning. Change your coolant!