Re: coating coolant passages in block and head of 1930 engine

Posted by Mr.Pushbutton  On 2008/5/15 7:08:42

Well, I'm the most vocal proponent of this, here and on the AACA forums. I learned this from a noted restorer and I know of severl others who believe strongly in this practice, and have been doing it for over 20 years with no ill effect. The practice is based on the premise that you are having the block and heads chemically stripped, not just auto parts store hot tanked. There is a big difference in the outcome. The auto parts store treatment degreases the parts, the chem-stripping cleans them to a fair-thee-well, the parts come back a bright silver color and the cooling passenges are perfectly clean--which also means they are bare cast iron, ready to rust again with the slightest provocation. I get the block (and heads and pans and anything else that doesn't move) back from the strippers, mix up a small batch of DP-90epoxy primer (PPG), it comes in many colors, most of us use the green color for engine work. I apply it with a brush to the rough cast sections of the block, inside and out and especially the cooling passenges. This involves taping off freeze plug holes and cover areas (straight eights), pouring the epoxy primer in and rotating the engine on the stand, even rotating it end-to-end using the cherry picker to insure coverage in unseen areas. Then we peel off the tape and sop up the excess. I know of Packard, Auburn, Duesenberg,Cadillac and other engines that were rebuilt over 20, 25 years ago and they are fine. I drove one in Warren in for the Packard centennial in that torture-parade and it ran cool as a cucumber. You still need to have a good radiator core that isn't clogged and a good pump and hoses and distribution tube, if so equipped.
The epoxy paint does not impede the heat transfer appreciably, and it staves off the re-corrosion of the bare iron cooling passenges.