Zincs for 427 Heat Exchangers

After the push rod failure in July 2012, I finally got the port engine all back together. But when I shut it down after the test run I noticed that the heat exchanger was leaking raw water out of the outboard brass drain plug. I put a wrench on the plug and was surprised when it practically fell off in my hand. There were practically no threads left on the plug! I was also surprised to see that the plug was only a plug when I expected it to be a pencil zinc. Since I knew of two pinhole leaks in that HEX, I decided to take it off and send it to Springfield Radiator to be boiled out and resoldered.

When I removed it, though, I found that the copper raw water intake pipe to the HEX was badly corroded to the point that it could easily have failed entirely at any time. The fact that the HEX doesn’t have zincs might explain why the threads were shot on the plug and the copper intake pipe was nearly gone—electrolysis 101. Unfortunately, I didn’t take pix of the damaged pipe, but when it came back from the radiator shop it was nicely boiled out and the shop had crafted a new intake pipe out of sheet copper.

Even though zincs aren’t on the original line card for this boat from Chris Craft, I decided to install them since a pencil zinc will fit and function as a “drain plug” on the raw water side. I found 2 inch pencil zincs online for $2.50 each (search online for 1/8” NPT pencil zinc). Here's the side-by-side comparison of the original, dezinced plug and the new zinc.

But when I went to install it the brass fitting crumbled to bits! Again, electrolysis 101—brass loses its zinc in salt water unless it’s protected by a zinc anode. So, off to the radiator shop it went again, this time to have another brass fitting brazed in.

I pulled out the standard plug the radiator shop had installed and put in the zinc.

I little teflon pipe dope to seal the threads, and this part of the job was done.

My total investment in repairing, resoldering, zincing and painting the HEX was $180, which is a fair chunk less than a new HEX. I put a few coats of spray paint on (can't get the Ford color anywhere local!) and began the install. I didn't get far before I realized Springfield Radiator screwed up. They installed the new pipe inlet nipple at the wrong angle! The straight hose from the gear cooler to the HEX can't make that bend!

Fortunately, I had some 1.25" hose with 90* bends in it that I was able to use. It's not the way Chris Craft did it, but I really don't want to go back to the radiator shop again. Fall is coming!

All’s good now. We’re going boating for the first time in a month tomorrow! Yea!