Originally Posted by Rookie

I did not put any holes in them. They come with 1 hole in them for air pockets. I will probably not drill any holes in them right away. I'll see where my pressure is an go from there. I also just put those in my Merc 420's w/ 500 EFI cam builds. Those engines ran hotter water and oil than I like with 420 stock hardware. Nothing like spending $160 on thermostats. Why do I do this again... lol

Originally Posted by ThisIsLivin

I run in water temps that range from 34 to 76 degrees. I have a 524CI BBC that's a GM Mark IV block with AFR heads and a Brodix HV2000 intake, and Lightning headers. I am running the Hardin stainless pump that I have ported for better flow with a crossover and racing 160 thermostat. It came with 3 3/16" holes and I still have the divider under the thermostat. I added a -10 line from back to front to even out the cooling. According to my lab grade IR temp gun the front and rear of my cylinder heads are with 2 degrees of each other. I have slightly modified the headers to allow for more flow as well. When running wide open across the lake I run about 165 on the gauge. idling for any length and I'm 140-150 if the water is warm. When Lake Huron is cold, I'm lucky to hit 130 pushing it. My oil cooler is a bit too small, but with Amsoil as long as I'm under 300 degrees I'm fine. I couldn't ask for a more consistent and even cooling system.

Originally Posted by getrdunn

those lightenings have a sound of their own don’t they... Also good info. Like abones mentioned every application can differ. I will be running large stat controlled oil coolers. I suspect they’ll only open on hard runs with lake mi water temps.

Originally Posted by getrdunn

Aside from the hole in the stats and your 5/16 restricter in your bypass is that your only source of cooling the exhaust until stats open?

Originally Posted by Rookie

No, I plumb the rear of the intakes into each header. I don't believe there would be enough flow if I didn't. Also at 120°F I'm assuming they will open relatively fast. I do plan to open the bypass to 3/8".
See 2nd pic post #8