I put the edelbrock victor jr. heads on my 400 block and edelbrock only stated to drill out the bottom steam holes in the heads and said do not drill out the top steam holes. I just used a head gasket as a template and started drilling. Ran the engine in 90 plus degree weather with no problems, runs about 180 at idle and about 190 cruising. Not sure what no holes will do though. Check with your head manufacturer to see what they recommend on the steam holes.