BB Mark IV coolant holes
 

Any opinions about drilling the two missing coolant holes on the early Mark IV block? I have stock cast iron heads and a set of FelPro 1027 head gaskets.

https://cimg5.ibsrv.net/gimg/www.cor...1bff435733.jpg

what block and heads do you have?

427 Mark IV block from 69, stock cast iron heads from 69.

Then ignore the page you posted about gen 5-6 stuff.

I respectfully disagree with Derek, I think you could drill the small holes as suggested by Felpro if you want to (parallel cooling I think). I wish I would have seen this when I did my rebuild, my 68 just has the #3 holes. Mine works but more uniform flow is better and obviously and Dart Merlins have the holes as an example.

Experts educate us please.

I didn't read that completely. I thought you wanted to drill out the holes in front. My 78 block has all 3 holes between and below the cylinders. Most head gaskets have a small hole there. Be conservative. Small holes, not 1 inchers...