Coolant flow question

[Da67goatman]

How does the coolant flow through a smallblock?  A diagram would be most helpfull.  Thanks.

[HAULIN IT]

There are a couple minor variations based on the year, heads, intake coolant passages & even the rad. The basic is this: The coolant goes into the pump & is pushed through the Two holes in the front of the block...this feeds around the cylinders, from there it goes upward into the heads, into the intake (one hose going to the heater core)...through the thermostat housing & back to the rad.
  Depending on which heads/intake you have effects how many places the coolant meet before getting to the front passage at the thermostat. Not sure what your after, but you want to keep in mind...all of the coolant doesn't "follow the leader" so to speak, the coolant basically ambushes the engine looking to get out (back into the rad) so not all of the water routes through the back of the block, heatercore, ect. it's more like a garden hose with several holes poked in it...coolant "gets out" at the first hole (the front series of holes going up to the front of the heads, some travels farther back & so on, some goes into the heatercore & back to the front. Understand? Hope this helps, Lorne

[Da67goatman]

So the water goes in 2 places and comes out 2 places, do they meet anywhere?

[1980c10]

So the water goes in 2 places and comes out 2 places, do they meet anywhere?

The lower radiator hose flows into the water pump where it is separated flowing through the block etc. The coolant flows back together in the intake when the water reaches a warm enough temp(typically 160-195) the thermostat opens and the water flows back together through the upper radiator hose. This also takes place in the heater core(essentially a mini radiator for your heater).

[HAULIN IT]

Well, I'm not sure I'm following you on the "come out 2 places, meet anywhere?" Do you mean each side of the block, As in INSIDE the block? No. Each side of the block has 8 or so places (just going from memory, may be more. 400's have additional small ones between the cyl's.) that the coolant goes out of the block up into the heads. Like I said, depending on the intake...some don't have a rear coolant crossover, but most stock type do...so out of the engine up into the intake would typically be 4 corners. The heater core hose comes off of the Right side & comes back in either to the top of the waterpump or rad. depending on which set-up it is. What is it that your trying to figure? Are you the fellow that was doing the overheating/by-passing the heatercore stuff? Let's start there. Lorne
 

[Da67goatman]

yep that's me with the overheating issue, I'm bringing it back up because my electric fan fried on me yesterday and since I'm changing the fan its one step more to change the radiator, if that's the reason its overheating.  So the coolant crosses paths at the intake?  If that's the case, my radiator is no longer doing its job and its time to upgrade to aluminum.  but I was under the impression that the coolant should still be able to get back to the radiator through the t-stat even if the heater core lines were closed.

[1980c10]

first check your radiator.

Feel the radiator fins as the engine warms up. As the thermostat opens, the entire radiator should start to get warm. If only part of the radiator gets warm, it may be clogged in the cold areas.

Another sign of a clogged radiator is overheating at highway speeds.

overheating at idle it is a sign of a bad fan or fan switch.

[HAULIN IT]

So the coolant crosses paths at the intake?  If that's the case, my radiator is no longer doing its job and its time to upgrade to aluminum.  but I was under the impression that the coolant should still be able to get back to the radiator through the t-stat even if the heater core lines were closed.

Yes, The only place the Two sides of the coolant in the engine meet is in the intake...I don't see how that makes it a "sure bet" that the radiator is bad, what makes you think so? In every SBC, coolant crosses in the intake...How does that not make every rad bad? I don't understand your reasoning.
 Yes, the coolant can still get back to the rad with the heater hoses blocked, plugged, looped, ect. if the thermostat is open. This is why I used the garden hose with holes in it theory...maybe not the best, but sorta applies. The heater core hose would just be one of the holes...the water still gets out the end, just that some of it went to the heater core. If you block it (or stick your finger over the hole) water doesn't go there anymore, but it still goes out the end like it was with the hole open, Does this make some sense? Ofcorse the truck system is a closed loop & not running on the ground..it was just the first thing I thought of hoping you could relate.
 Have you tried removing/changing the thermostat? If it is stuck shut, no (or a little if you have the set-up with the heater hose going in the rad tank) coolant is getting back to the rad. Maybe this is why it didn't overheat when you didn't have the heatercore valve shut? Lorne

[VileZambonie]

DA67, First understand it is a sealed system (to an extent) and when cold there is still coolant in the radiator and all of your passages only the waterpump is circulating the coolant through the bypass side of the circuit, around the cylinder walls, cylinder heads, heater core etc. Heat is transferred through the coolant transferring the heat energy to a source of less heat constantly. Once the thermostat opens coolant is circulated through the radiator where again heat energy is transferred to the source of lesser heat but at a grater rate and volume. You can't think of it as a direction the coolant takes, you need to think of it as a heat exchanger with a control valve.

Now- if it's overheating look at the basics assuming you've verified the system is full:

When does it overheat? If it's a clogged radiator it won't overheat until the thermostat opens and there will be a cold spot in the radiator. Is the thermostat opening? Is the upper hose hot? What about the lower hose? If your fan isn't working that's a good reason to overheat right there. What kind of electric fan do you have and what controls it? Are you using a shroud? Try putting your mechanical fan back on and see what it does.

[Da67goatman]

It only overheats when the valves are closed. The fan worked almost too well, it cools so good that sitting still, the gauge will actually continue to drop incrementally farther every time the thermostat opens.  I have the fan wired through a fuse block and a thermostat.  Manufacturer stated that the fan draws 12.5 amps so I put it on a 15 amp fuse, still good.  2 days ago The fan self destructed on my return trip from the scrapyard.  I was a mile from home with an empty trailer, when we smelled burning wires, so we pulled over, popped the hood and the fan was billowing smoke.  So I unplugged it and went home, gauge stayed at 210 the whole way, no over heating.  I do remember feeling the radiator heat up faster in some spots than others, that means its clogged in certain tubes right?  I have another fan that I am waiting to put in,  draws 16 amps, but is the same size, 16".  The reason I asked this topic was that I thought since I closed the heater core hoses, that side of the coolant system stopped flowing, but now I know that the coolant crosses in the intake manifold.  Now I'm thinking that radiator is plugged in some spots.  Thanks guys, you're a big help.

[1980c10]

 "So I unplugged it and went home, guage stayed at 210 the whole way, no over heating.  I do remember feeling the radiator heat up faster in some spots than others, that means its clogged in certain tubes right."

This is some what of a sign that your radiator is good, your fan wouldn't usually run at highway speeds. the radiator will usually run hotter near the top

you could remove both radiator hoses and cap-run a garden hose in the top and watch from the the cap to see if water runs through.

If your heatercore tube are blocked with the heater core bypassed-try loping it and see if it helps