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Quick idea about a slight modification to the proven coolant reroute...

Old 12-10-2009, 12:47 AM
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Default Quick idea about a slight modification to the proven coolant reroute...

OK. I've been getting the idea that with the typical 'back of the head t-stat' reroute that the front of the block/head maybe run a little warmer than the back. It seems every reroute diagram that I found had the heater core being fed from a fitting on a spacer on the back of the head and the front coolant neck getting blocked off. I got to thinking, what about using the front waterneck to feed coolant to the heater core to promote flow through the front of the block/head? This still allows the same flow of coolant as before. I mean, this could easily be accomplished for those who didn't pull the neck and shove a freeze plug (like myself) by using the stock outlet pipe that originally fed the heater core. Yes?

On a side note, would it be possible to run the heater return to the upper radiator hose right at the radiator? (green "?" on attached diagram).

Eh.... just thinking of stuff to do...knowledge to gain.

(btw.. I didn't picture all the other stuff...oil cooler, TB, turbo...because the lines running to those work just fine as-is).
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Old 12-10-2009, 01:34 AM
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Just free-thinking here...

My intuition is that the front of the head/block would run slightly cooler than the back, as that's where the coolest coolant is.

I think I understand your train of thought, but allow me to throw a switchtrack: Just because no coolant is exiting from the front, it does not mean that no coolant is flowing through the front.

That was the big problem with the original design- taking so much water out of the front meant that there was more coolant flowing through the front of the engine than the back. With both the thermostat and heater core exit at the back of the head, the volume of water flowing through all parts of the engine should be more or less equal. Ok, there's maybe a tiny bit less coolant flowing around the very front of the #1 chamber, but the coolant that is flowing around that area is cooler than the coolant flowing around the #4, as the latter has been pre-heated by a greater amount during the process of getting there.

Discuss.
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Old 12-10-2009, 07:16 AM
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I agree with Joe...but your diagram is exactly what I'm running right now...and I've been hesitant to switch the heater core feed to the back.

I like the idea of still having some coolant exit the front, but when I think about it I'm really wasting coolant capacity. That coolant has barely traveled the 7in from the pump up to the neck, and is only cooling the front half of cylinder one.

As we all know water has a high thermal capacity, and this relatively cool water could easily remove it's share of heat all the way up to the top of the #1 cylinder head passages, and flow thru the head with the rest of the coolant.

Also, Mazda designed these engines to work like this. Despite our eleventybillion coolant reroute threads, we haven't even touched the amount of real heat transfer work they did when they first put this motor in the 323.

Additionally...I HATE that damn hose that runs from the front all the way to the heater core. It's long, has to pass straight over the exhaust manifold, and comes to the copper fitting at a funny angle that caused it to leak the first time around. This could be remedied with some creative work, but that effort would be better spent working on a nice spacer.


Spacerless reroute was easy to knock out and drop average coolant temps ~10*...but it's not ideal. In the midst of studying for finals I'm working on the different ports and locations I need machined into this blank spacer.
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Old 12-10-2009, 09:44 AM
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...and this is why I ask such questions on here rather than somewhere else

With that said, is there any possibility that the air coming in through the radiator and flowing over the front of the engine/head, actually has an effect on cooling the engine/moving heat away from the block?
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Old 12-10-2009, 10:32 AM
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Originally Posted by Doppelgänger
OK. I've been getting the idea that with the typical 'back of the head t-stat' reroute that the front of the block/head maybe run a little warmer than the back. It seems every reroute diagram that I found had the heater core being fed from a fitting on a spacer on the back of the head and the front coolant neck getting blocked off. I got to thinking, what about using the front waterneck to feed coolant to the heater core to promote flow through the front of the block/head? This still allows the same flow of coolant as before. I mean, this could easily be accomplished for those who didn't pull the neck and shove a freeze plug (like myself) by using the stock outlet pipe that originally fed the heater core. Yes?
There were people at miata.net running with the exact setup you describe. Maybe search the forum there for threads about their results
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Old 12-10-2009, 02:01 PM
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Originally Posted by Doppelgänger
OK. I've been getting the idea that with the typical 'back of the head t-stat' reroute that the front of the block/head maybe run a little warmer than the back. It seems every reroute diagram that I found had the heater core being fed from a fitting on a spacer on the back of the head and the front coolant neck getting blocked off. I got to thinking, what about using the front waterneck to feed coolant to the heater core to promote flow through the front of the block/head? This still allows the same flow of coolant as before. I mean, this could easily be accomplished for those who didn't pull the neck and shove a freeze plug (like myself) by using the stock outlet pipe that originally fed the heater core. Yes?

On a side note, would it be possible to run the heater return to the upper radiator hose right at the radiator? (green "?" on attached diagram).

Eh.... just thinking of stuff to do...knowledge to gain.

(btw.. I didn't picture all the other stuff...oil cooler, TB, turbo...because the lines running to those work just fine as-is).
its funny I was thinking about the same thing the other day, im doing a build atm so have the engine out but dont really want to use a spacer or drill into my head, moving the rear heater water neck to the front would allow me to have heater core access as well as temp sensor access, in saying that i do like the bare look of the front of the engine with just a freeze plug in the head rather then the long neck.....

Ive never had cooling issues but havent really pushed the car since i put the turbo on it, but figured the reroute cant be a bad thing, im also thinking about getting a twin core radiator to help things along...

would love to know which way people with the reroute think i should go...
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