What makes antifreeze go from alkaline to acidic? Does combustion gas leak from the head gasket and contaminate it or is it the heating and cooling process? Regardless, we have had two corrosion situations from acidic coolant recently, a pair of 330 cylinder heads and the core plugs in a 365 GTB/4 Daytona. To be fair, the core plugs are very soft alloy in comparison to the engine block so they are kind of sacrificial, unfortunately they are difficult to change. These plugs were so delicate that just by scraping the crusty coolant off to find the source of the leak, the screwdriver poked right through them like they were made from waxed paper.

Ferrari 365 Daytona Engine repair

Ferrari 365 Core Plugs
The 330 heads are a combination of a bad casting and corrosive coolant. I saw a youtube video showing the process of building a modern Ferrari 612 engine where an MRI test was used to determine the thickness and integrity of a cylinder head casting. They didn’t have this technology in 1966 and this is the evidence of it! The deep pores in the exhaust port aren’t from corrosive coolant, it’s from a horrible casting. The pitted areas around the water passages are due to corrosive coolant rotting the material away.

Head Gasket leaking on Ferrari 330

Welding holes in Ferrari 330 V-12
Like a dentist, I drilled and scraped the corrosive material out so I could weld the holes that were leaking coolant into the exhaust and intake ports. I don’t often remove valve seats and realize what a difficult job it is but I found a great way to get them out easily. I take a valve with the same size stem as the original (8mm for Ferrari) but has a slightly smaller head. I weld the head to the seat and drive the valve and seat out with a hammer from the back side!

Repairing 330 GTC Heads
Anyhow, after welding, grinding, pressure testing a number times, I finally have the heads sealed up and looking great. After grinding and cutting the core plugs out of the Daytona block, we installed the new ones and sent the car home.