HeavyOlds

I installed this -12 hose from the back to front of my intake manifold.
I was told to make sure and connect my heater hose to help cool the engine so I added this hose to the other side to get the hot water out of the back of the head. Would this help, hurt or do anything at all?

Fun71

It looks as if it would allow coolant to bypass the head, which does not sound like a good idea.

HeavyOlds

I think I saw one of the Olds gurus do this. The water pump pushes coolant into the block and is warmed by the cylinders before it goes up into the heads. I think the idea is to get the hot coolant out of the front and back of the head so that the hot coolant doesn’t have to flow from back to front through the head, heating up as it goes. I’m second guessing now whether or not this is what happens when you put a hose from back to front. Did the Olds guru properly test this out to make sure it helps?

Olds64

The Olds engines weren't designed that way from the factory. There's no need for it. I've never even heard of this mod on high performance race motors. If it were my car I would remove it.

JohnnyBs68S

I'm surprised Joe hasn't jumped in on this yet, but if you bypass some of the coolant flow through the heads, the heads will run hotter, which is never a good thing.

My understanding is that the water pump pushes coolant through the block from front to back cooling the cylinder walls, then it flows up into the heads at the back and flows towards the front cooling the heads. Adding a hose such as this bypasses that coolant flow through the heads, reducing it rather than enhancing it.

oddball

All-out race builds that still have water in them will use 4-point cooling. They also tap the driver side of the intake manifold and run hoses from both back corners to the front of the intake. The theory is they get more consistent temps in the heads. It's not about cooling - it's about consistency.
For street it's useless and can be harmful. There should be a restriction down to about 1/4" from that port. The stock heater cars had it in the fitting, the A/C cars had it in the control valve. Otherwise too much water can flow through there and you limit the flow in the driver's head and the front half of the passenger head.

There's a number of coolant passages through the head gasket. The largest ones are along the outside wall, biased towards the center. It's not really back-to-front in the head. I mean, that's the hope, but more just because the outlet is at the front than because of how the passages are designed.

Schurkey

I'd be willing to believe that in certain competition circumstances, (heavy throttle for extended time) adding a pair of small-diameter (-4, nominally 1/4 inch) hoses from the rear of the heads to the rad side of the thermostat, could eliminate steam pockets (NOT AIR, there is no air in the system after the cooling system has been burped after service) under high-power engine use. Street use? Total waste of time, money, effort, and enthusiasm.

Bigass hoses like what is pictured, routed to the restricted side of the thermostat...sounds VERY silly to me under any circumstances.

Might also consider that even the OEM Olds heater system, which pulls heated coolant from the RR of the intake manifold, uses restricted fittings, not full-flow. So the hose may be huge, but the coolant flow is relatively small.

76olds

Would this help, hurt or do anything at all?

I agree with others. In fact, you won't get any flow going through the added hose. It won't hurt anything so if you don't mind looking at it, just leave it as is.

Eric

Schurkey

Thermostat closed, no flow.
Thermostat open, coolant bypasses the cylinder head picking up no heat from the engine. Cylinder head runs hotter. Counter-productive.

76olds

The hose installed is up higher than the T-stat , unlike the constant flow on heater hose side of the water pump. How would that hose effect any cylinder head flow, T-stat open or closed ?

Schurkey

"Higher" has nothing to do with it.

The hose connects to the intake manifold water crossover. This is on the restricted side of the thermostat when the 'stat is closed. The only water flow will be through the bypass hose. The volume of flow with the 'stat closed is small enough to be ignored.

'Stat open, there's plenty of flow through the water crossover. At that point, it's a matter of "path of least resistance" whether the coolant will flow through the twisting, turning water jacket passages of the head usefully picking up heat, or through two nicely-streamlined 90 degree hose ends and the straight length of hose. Given the volume of water going through the engine, there'll be flow through the head and the hose--but the coolant flowing through the hose isn't doing anything useful for the head.

joe_padavano

I've been at Spring Carlisle all week.

Besides, I think you have it covered.

76olds

Fair anuf.
However, with the amount of coolant flow running through the intake crossover into the head given the "path of least resistance" . This happens. On a cold engine start-up, the hose will begin to fill. Once the hose becomes filled with coolant and the system builds pressure, the flow will no longer pass through the added hose along the top of the intake.
"Higher" does have something to do with it. .

Schurkey

You have it backwards. The coolant doesn't flow from the intake crossover INTO the head or the added hose. It flows from the head or the added hose TO the intake crossover.

Once the hose fills, it's never going to un-fill as long as the hose is lower than the level of coolant in the radiator.

Of course not. The water pump is pushing the coolant along. System pressure (the pressure from the radiator cap) may be equal everywhere in the cooling system, but dynamic pressure (from the water pump) will vary along the coolant circulation path--higest at the pressure side of the pump, through the engine, past the thermostat, into the radiator, and back into the suction (low pressure) side of the water pump. In this case, the rear of the head (where the added hose connects) is going to be somewhat higher pressure than in the intake crossover if the thermostat is open. Coolant flows through the hose and through the head, past the thermostat, and into the radiator.