Cooling mods for Pontiac 389 400 455

[@sampson7941]

Dont have any of that on my 467 and stays cool just fine. I like what your doing there though. Another guy has a video up doing the same thing. Monty's garage or fast monty or somethin

[@CrankAddict]

Yeah, I talked to him about my ideas as I was making my video. His idea is simple and has some tuneability to it, but I think my idea is more efficient.

[@scotthatch4548]

I have never understood why people want to bypass water flow around the head and not cool the head as well ....

[@Wei55_und-stolz]

Hi, can you please confirm the tap size that you used for the back of the heads? I’m sure my ports are larger than 1”. Cheers

[@CrankAddict]

a 1" NPT tap is bigger than 1" diameter.

[@DisturbedBlodgett419]

Where did you end up routing your heater core hose to?

[@CrankAddict]

The rear passenger water outlet has a T fitting. This fitting goes to the heater core and has an inline shutoff valve so I can turn off the heater when not needed (so its always shut off).

[@mayken6661]

68 GTO . New electric fan, new high flow water pump, not sure of brand or material, with thermostat/without… Still runs HOT as F**k !

[@CrankAddict]

make sure initial timing is at 10-16 degrees BTDC. Your timing marks could be wrong on damper. Could be a clog in coolant system. Can you see water flow through radiator with cap off? Try to plug the bypass on the waterpump to keep hot water from mixing with the cool water. As a last resort you can tap the rear water outlets like I did. Its a lot of work with engine in car, though. There could also be excess friction in engine, like spun bearing or ring problem(how does the engine turn over with socket on crank pulley?) How is compression when cranking (too high? too low?) lower radiator hose has a good spring inside?

[@56cadd]

Drill 2, 1/8 holes in a 180 thermostat and use 16 psi lever cap for burping the coolant system.

[@terrypetty9822]

So the coolant has cooled the back cylinders then goes through the heads back to the t-stat housing. Now you are taking some of that and routing it back to the same place. Explain how that alone will improve anything. The heater valve will make a difference. Restricting the t-stat bypass is risky especially when refilling the radiator and that orifice will plug easily. The Vortec 350 Chevy has the absolute best t-stat bypass system using the double seated t-stat that when closed opens the bypass (up position) but when open, (down position) closes it. Make one do that and I'll be impressed. With that removeable cross-over and a tig it can be done.. Then 100% of the coolant will be COOLED.

[@CrankAddict]

My TIG skills are not good on old aluminum. Opening the heater valve actually increases water flow to the rear cylinders on that side of the engine (if you don't do my mod). The idea with this mod is to get water to flow THROUGH the rear cylinders and return it to the t-stat. Without this mod the water doesn't circulate well through the rear cylinders. Imagine a large swimming pool where the pool pump and the drain are on the same side. The t-stat bypass is not needed AT ALL if you drill a couple of 1/8" holes in your t-stat. You don't want to send hot, bypassed water back into the engine.