Cooling Mod #4 question

[kwimmer]

Head drilled for cooling mod, will block bottom of t-stat housing and run line from end of head through heater core and back to bypass inlet on water pump. Straightforward
My question. Size of drilled hole matches up to 3/8 Id hose. Is this large enough for proper coolant flow or do I need a larger diameter to allow the mod to work?

[4 l-bodies]

Thermostat needs to have coolant flowing by it so you don't get wild temps swings when it decides to open. IMO and experience, bad idea to block off the bottom of T-stat housing on a street car. To reply to your question, yeah 3/8" ID doesn't really equal 5/8" ID does it? Doing what your planning on doing doesn't rally gain you much of anything. Why not just add coolant (outlet of waterpump) to your #4 mod or have it return to waterpump (suction side) leaving everything else as factory?
Todd

[tryingbe]

I drilled a hole on top of the waterpump housing and ran the hose there.

[Pat]

I have used 1/4" brake line for years with no issue. I suspect it's moving enough coolant to be effective given the motor has cast pistons and has had the snot kicked out of it for years at the 325+hp level with no (knocks on wood!!!) broken pistons.

[4 l-bodies]

I have used 1/4" brake line for years with no issue. I suspect it's moving enough coolant to be effective given the motor has cast pistons and has had the snot kicked out of it for years at the 325+hp level with no (knocks on wood!!!) broken pistons.

Pat, OP is talking about feeding heater core with 3/8' line instead of the 5/8" line factory used, and omitting factory bypass at thermostat. Are you feeding coolant to it (from WP outlet) or relieving pressure from #4 coolant mod (to WP suction)? It's been done both ways with apparent success.
Todd

[Pat]

My mistake...should have read more carefully!

Scratch what I said. In my set up, I'm not running a heater core at all...the motor has been in a race car the entire time. I'm running a 1/4" line from the suction side of the pump to the side of the head. My logic was to keep cylinder head temperature consistent across the head...in other words, not pumping colder coolant directly to #4 when the rest of the head is getting coolant that has already run through the block.

Without the heater core, to keep coolant moving past the thermostat so there aren't huge temperature swings, I have a couple of fairly decent sized holes drilled in the T-stat. For a race car, this has worked for me just fine. Warm up is a bit slower but it gets to operating temp just fine and no huge temp swings.

Again, sorry for the confusion. Won't read/post from my phone anymore! ;-)

[Shadow]

Head drilled for cooling mod, will block bottom of t-stat housing and run line from end of head through heater core and back to bypass inlet on water pump. Straightforward
My question. Size of drilled hole matches up to 3/8 Id hose. Is this large enough for proper coolant flow or do I need a larger diameter to allow the mod to work?

We've been doing it this way for years. Just make sure your T-stat is modded with hole in it and there will always be coolant flowing through it

Having said that, I have always used the Full 5/8 hose to the heater core, but on some applications, where the factory rad was Not working 100% I had to place a restrictor inside that 5/8 hose or else the motor would not cool properly. (coolant takes the path of least resistance and circulates through heater core instead of rad!)

So the 3/8 should work fine, but you could always tweek it up to 1/2" ect and just monitor the way the motor cools vs heats (in cabin) to really dial it in.