Fredrik71

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.

derekderek

what block and heads do you have?

Fredrik71

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

derekderek

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

suprspooky

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.

derekderek

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...