Head Cooling - What I was talking about

[Zed Head]

Started a discussion over on Stanley's thread (link below) about bypassing the heater core and its effect on cooling. http://www.classiczcars.com/forums/interior-s30/49100-dump-heater-keep-fan.html#post428554

Didn't want to muddy up his thread so I've posted a couple of pictures I took to show what I was talking about over there.

The first shows the large passage at the back of the head which should flow a lot of the coolant up through the block and through the head from back to front. The heater core supply hose fitting has been removed and is lying on the head. The second shows my finger in the big passage and visible in the heater core supply passage. That's what I think would be the shortcut for the coolant if a large hose is attached to the fitting and coolant allowed to flow freely.

Only posting for the record and the discussion. Not trying to win, it's just an interesting topic.

[LeonV]

Started a discussion over on Stanley's thread (link below) about bypassing the heater core and its effect on cooling. http://www.classiczcars.com/forums/interior-s30/49100-dump-heater-keep-fan.html#post428554

Didn't want to muddy up his thread so I've posted a couple of pictures I took to show what I was talking about over there.

The first shows the large passage at the back of the head which should flow a lot of the coolant up through the block and through the head from back to front. The heater core supply hose fitting has been removed and is lying on the head. The second shows my finger in the big passage and visible in the heater core supply passage. That's what I think would be the shortcut for the coolant if a large hose is attached to the fitting and coolant allowed to flow freely.

Only posting for the record and the discussion. Not trying to win, it's just an interesting topic.

I'll quote a few statements I made earlier...

Shorting the back of the head to the pump inlet creates issues. Creating a path from the back of the head to the radiator only helps to improve things.

The whole reason for the head being hot in the back is that the thermostat is in the front, as is the water pump. The path of least resistance is to the front of the head, thus the back gets less cooling. By creating a path from the back of the head to the radiator, you are working to equalize temps, not the other way around as you infer.

What Tim and other guys are doing is a better solution as they tap into multiple (or "better") spots in the head, but that doesn't make routing a small line from the back of the head to the radiator inherently "bad".

You need to see the big picture here. Temps at the back of the head have been measured to be hotter than the front. The "bad" thing to do is to short the back of the head to the water pump inlet. This raises coolant temperatures (because of bypassing the radiator) and further increases chances of overheating at the back of the head.

Plugging the back of the head puts you at square one.

Routing the back of the head to the radiator only helps to improve things. This would help promote flow at the back of the head. More coolant flow = more cooling. Less flow = less cooling and increased chances of nucleate boiling. It should be clear that there should be some restriction in the line.

Look at the (somewhat undetailed) drawing in the Cooling section of the FSM, page CO-1, if this is unclear.

[LeonV]

I can't agree. You're inferring from very little evidence. There's no real difference in flow through the head determined by where the coolant goes, whether it's back to the pump inlet or back to the radiator. In effect, going to the pump inlet pumps less water through the radiator. If the flow through the engine and thermostat was barely enough to remove the heat produced, you could argue that diverting hot water back to the inlet pushes things over the edge. But I haven't seen enough real evidence of why the overheating occurs. Most of the theories suggest that "spot boiling" over 5 and 6 is the initiation of a reduction in cooling capacity overall which then leads to overheating in general. The hole drilling and plumbing is intended to move more water over 5 and 6.

I understand what you're saying I just haven't seen real evidence for it. Even in all of the pages of the head cooling thread on Hybridz. Lots of conjecture, some experiments with hole drilling and re-plumbing and some subtle results, but little understanding/explanation of what's really happening in the engine and head.

Conjecture? Subtle results? Temp readings at different points of the head, while at steady state on an engine dyno issounds like a good procedure to me, with very conclusive results to boot!

Heat Transfer is not voodoo. The back of the head is hotter because it receives the hottest coolant and the least amount of flow. You improve cooling by either increasing flow, delivering cooler coolant, or both.

Exactly how much more evidence do you need?

If what you're suggesting is correct, then my statement about running the heater core supply back to the radiator directly would be a good idea, and cheaper than the hole-drilling an re-plumbing . Maybe it should be suggested over on Hybridz. It would be a lot easier than what's being done now.

I've been saying all along that running it to the radiator would be a better solution to plugging (with a properly restricted line) and much better than looping. The evidence very strongly points to it. What got me thinking originally was John Coffey's post about how he's routed the heater supply to the thermostat housing. While that may be effective (I don't know), I concluded that routing it past the thermostat was a better idea, since you'd be in more control over where this coolant is flowing.

If instrumented testing proves me wrong, I'll happily eat my words.

[Zed Head]

I've been saying all along that running it to the radiator would be a better solution to plugging (with a properly restricted line) and much better than looping. The evidence very strongly points to it. What got me thinking originally was John Coffey's post about how he's routed the heater supply to the thermostat housing. While that may be effective (I don't know), I concluded that routing it past the thermostat was a better idea, since you'd be in more control over where this coolant is flowing.

If instrumented testing proves me wrong, I'll happily eat my words.

From my view, the onus is on you to provide the data from the instrumented testing or a link to someone else's work, from an engine with the heater core supply line back to the radiator or the thermostat housing. You're making unsupported claims. Thought experiments. Conjecture. Supply the data, or the link to the data. It's just a BS session without it.

Edit - Just to simplify - what we're really talking about here is the difference between drilling holes in to the cooling passages on the driver's side of the head (left) and plumbing that coolant flow to the thermostat housing versus just running the heater core bypass line to the thermostat housing instead of the heater core. That is the heart of the discussion. Much much easier and cheaper to just run a hose from the fitting already installed at the back of the head. Why isn't that the answer to the problem? That's the question that needs real data.

Edited April 10, 2013 by Zed Head

[LeonV]

From my view, the onus is on you to provide the data from the instrumented testing or a link to someone else's work, from an engine with the heater core supply line back to the radiator or the thermostat housing. You're making unsupported claims. Thought experiments. Conjecture. Supply the data, or the link to the data. It's just a BS session without it.

Edit - Just to simplify - what we're really talking about here is the difference between drilling holes in to the cooling passages on the driver's side of the head (left) and plumbing that coolant flow to the thermostat housing versus just running the heater core bypass line to the thermostat housing instead of the heater core. That is the heart of the discussion. Much much easier and cheaper to just run a hose from the fitting already installed at the back of the head. Why isn't that the answer to the problem? That's the question that needs real data.

Actually, this conversation originally stemmed from your assertion:

I'm no expert on how these engines work but the guys who modify for more power and/or race have shown that allowing coolant to flow at a high rate out of the back of the head back to the radiator will cause imbalanced cooling and increase the chance of overheating. The heater core only bleeds a small amount of the flow that is passing up through the block to the back of the head then forward to the thermostat housing. When a hose is run directly from the back of the head back to the radiator, flow through the head is diverted.

Most recommend blocking the port at the back of the head instead of rerouting it. This forces the coolant to pass through the head as designed, removing heat along the way.

Just passing on some knowledge from other forums.

Your claims were the ones that were completely made-up and unsubstantiated.

[Zed Head]

Round and round...

I expected better. Oh well.

[LeonV]

Right...

Let me ask you this: have you ever done any sort of your own instrumented testing? Have you invested your own time and money just to prove that you're right to some guy on a forum?

I've posted test results on other subject matters as others elsewhere have used their time to do proper testing on their own coin, and then posted it on a public online forum. If you so badly want me to set up controlled, instrumented testing on this subject, I'm happy to do so if you pay me for my time, supplies, and dyno time.

You like to complain about how others don't have "conclusive" evidence, yet you never seem to have your own. Maybe we should ONLY talk about things that have been "conclusively" proven, because apparently everything else is just worthless BS. I'm sorry that I applied fundamental engineering principles, related empirical evidence, and logic in an attempt to describe a physical phenomenon. Guess that's just bull**** too.

Moving on...

[John Coffey]

I actually have some test results from what Electramotive did back in the 1980s with the turbo engines. Got them from Dale Caldwell. The best solution is what they did on their racing engine which was to drill outlets on left side of the head on in 5 places and route those outlets to a manifold and then route that manifold to the radiator. They completely blocked off the heater outlet on the right side of the head.

For low power (under 200hp) race engines I run a -4 line from the heater outlet to the bottom of the thermostat housing for three reasons:

1. Air bleed so radiator filling is a bit easier.

2. Duplicate the factory bypass when the thermostat is closed (I also drill two .125" holes in the thermostat if I'm running one in the race engine).

3. Slight increase in coolant flow at the back for the head where it needs it the most.

And no I'm not going to publish the test results for the same reason I don't post copies of the 3023 homolgation documents that I have. This stuff cost me money and no one here is paying me. I offer advice and if you want to take it, fine.

[Zed Head]

Thanks John. This whole conversation is about the difference between routing the heater outlet to the pump inlet or routing it to the radiator or thermostat housing. Started when I said in another thread that sending the coolant back to the radiator has been shown to be worse than blocking the port, when the typical bypass is done by sending it back to the pump inlet, not the radiator, so I had no basis for my statement, which I acknowledged later. It was a mental typo, radiator instead of pump inlet.

My ending thesis after the word battle is that the Electromotive method of drilling the holes in the head indicate that there's more to the situation than just where the coolant ends up, in the inlet or at the T-stat housing. It's where you pull the coolant from that matters. Otherwise the guys that know, like Electromotive, would just run a hose from the heater supply port at the back of the head to the thermostat housing and get the same results.

If we could get past the butting of heads, it's probably easy to answer. Maybe someone has even tried it and knows.

[240260280z]

Here is the Nissan S20 engine with a similar cooling architecture implemented that John mentions above. This engine collects along the top of the block:

[LeonV]

Nice photos Phil. Something like that will definitely distribute coolant flow better than a single or dual exit.

[240260280z]

Here is the coolant input for that motor. Same flow pattern: