xxdabroxx wrote: ↑Thu Dec 23, 2021 5:18 pm
I picture what's going on under the deck of a SBC similar to a log style exhaust manifold but backwards. In through one hole and out through the many ports in the deck. The head gasket is like a metering block of sorts and depending on the head gasket the bulk of the coolant flows up the middle. This high flow in the middle would likely fight the flow from the rear to the front in my opinion. Fluids generally take the path of least resistance. (I'm no fluid engineer though)
Correct, running all coolant flow back thru the head in a parallel flow system is only good from a mass production standpoint to use less connections, hoses etc (simplicity), it works well enough. Then consider the coolant flow area around a factory head with thin deck, small port runners etc V's the same dimension head externally with thick deck, thicker casting areas, bigger ports etc.
The claims of the rear coolant outlet on a parallel flow cooling system taking away flow that was meant for cooling in the head and only reading lower temps on the gauge due to the coolant having picked up less heat are rubbish. If this was the case this would be evident in overall tunability not being as consistent.
Don't know how many times I need to post this. Earlier in this thread I posted the flow for a Pontiac 6 cyl. All the US V8 engines of the 60s,70s etc used the same basic design: water INTO the block; water OUT through the heads. The only engine that I am aware of that used reverse cooling was very early Pontiac V8s, that fed water into the heads & exited the block. This only lasted a couple of years before reverting to the conventional method. I imagine the extra cost & not much benefit were the reasons for the demise of this set up.
Smokey Yunick agrees with the factory routing [ with one minor exception, later ] & says:
' ..the coolant flows [ from the pump ] to the rear of the block-receiving heat from the cyl bores- & when it reaches the rear, it moves upward into the cyl heads through the large interconnecting passages in the block & head........And once the coolant is in the head, it is forced back towards the front..'
Yunick does away with the coolant xover at the front of the intake. Instead, he has a Y piece that connects to the front of each head that leads to the t'stat & then rad. He claims this idea reduces turbulence & increases flow by at least 25%.
Further: ' I think it is important to force the major portion of coolant to stay in the block, until it reaches the rear transfer passages [ into the heads ]. It will then travel the full length of the cyl head as it returns to the front of the engine. This is the way the stock Chev system was designed to work and- if you discount elaborate external plumbing- this pattern seems to provide the most effective heat transfer to the coolant.'
Further: ' I think it is important to force the major portion of coolant to stay in the block, until it reaches the rear transfer passages [ into the heads ]. It will then travel the full length of the cyl head as it returns to the front of the engine. This is the way the stock Chev system was designed to work and- if you discount elaborate external plumbing- this pattern seems to provide the most effective heat transfer to the coolant.'
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Geoff2 but this is not how the sbc coolant is routed. There is no rear transfer passage.
cjperformance wrote: ↑Fri Dec 24, 2021 3:30 am
Further: ' I think it is important to force the major portion of coolant to stay in the block, until it reaches the rear transfer passages [ into the heads ]. It will then travel the full length of the cyl head as it returns to the front of the engine. This is the way the stock Chev system was designed to work and- if you discount elaborate external plumbing- this pattern seems to provide the most effective heat transfer to the coolant.'
Geoff2 but this is not how the sbc coolant is routed. There is no rear transfer passage.
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I would presume he is talking about the rear coolant holes that transfer into the heads Anyway, cant believe sometimes its the simple things that can't be understood and seem to go forever. Good luck and enjoy.
cjperformance wrote: ↑Fri Dec 24, 2021 3:30 am
Further: ' I think it is important to force the major portion of coolant to stay in the block, until it reaches the rear transfer passages [ into the heads ]. It will then travel the full length of the cyl head as it returns to the front of the engine. This is the way the stock Chev system was designed to work and- if you discount elaborate external plumbing- this pattern seems to provide the most effective heat transfer to the coolant.'
Geoff2 but this is not how the sbc coolant is routed. There is no rear transfer passage.
I would presume he is talking about the rear coolant holes that transfer into the heads Anyway, cant believe sometimes its the simple things that can't be understood and seem to go forever. Good luck and enjoy.
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What I always find interesting in this discussion every time it comes up is the complete lack of consideration as to the engines use and how it affects the flow within block/heads. In other words none of the opinions ever given are worth $.02 without pump type /rpm of pump/flow at said rpm/ drag or endurance/etc..
Rear transfer passage. Smokey is referring to the passages at the rear of the block that move coolant through the head gasket into mating holes in the heads.
OK,just to stir the pot an Sb2.2 valley pan has rear water outlets connected with passages to the front just like the -8 or -10 hoses from the rear to the front accomplish. There is also a -4 hose from pump suction side to center ex ports along with holes drilled between each pair of valves from ex side to intake side to vent steam/cavitation pockets.Does this mean every "race head" needs such? Bear in mind that this is old Nascar stuff operated continuously at near redline for hours on end before you answer.
ANother consideration is how much pressure your cooling system operates at. If using a lower pressure radiator cap as far too many do you will have cooling issues sooner than if running a high pressure cap. Remember that the boiling point for coolants is raised as the pressure is increased. Some top teams pre pressurize their cooling systems to raise the running pressure even higher. Some run as much as 50 or so PSI. Water boils at 212° F. 50/50 coolant boils at 223° F. The boiling point goes up 3° F for every pound of pressure (psi). A 15-psi radiator cap will raise the boiling point by 45° F. With the proper Coolant Mix and Radiator Cap, the maximum temperature is raised from 212° F to 268° F. and at 50 psi the boiling point is raised to 373*. You will never need it that high(and any normal radiator will not like you if you try) but the cooling system damn sure isn't going to develop any steam pockets either.
Geoff2 wrote: ↑Fri Dec 24, 2021 4:39 pm
CJ and others.
Rear transfer passage. Smokey is referring to the passages at the rear of the block that move coolant through the head gasket into mating holes in the heads.
Read your quote below a few times while studying the coolant flow path in an sbc, in particular read the part in bold. Then look again at an sbc head gasket and look for these "large interconnecting passages". You either have him referencing a different engine brand OR referring to a series flow BBC as this 'again' is not applicable to an SBC.
"Smokey Yunick agrees with the factory routing [ with one minor exception, later ] & says:
' ..the coolant flows [ from the pump ] to the rear of the block-receiving heat from the cyl bores- & when it reaches the rear, it moves upward into the cyl heads through the large interconnecting passages in the block & head........And once the coolant is in the head, it is forced back towards the front..' "
Geoff2 wrote: ↑Sat Dec 25, 2021 2:25 am
No, SBC. You should read Smokey's Power Secrets book. He details things that were tried to improve on the factory cooling.
Geoff , where are these "large rear interconnecting passages between head and block" on the sbc?
So now lets just imagine then that smokey bored some large rear passages of his own and had a series flow gasket made etc, this is still not relevant to a parallel flow setup with a rear outlet.
(Pics from net for examples, not my pics)
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What becomes obvious in these sbc coolant flow topics is that at least 99% of the posters have huge misconceptions as to how and where coolant flows through head/block.
1.Coolant is discharged from the water pump into both banks of the block at a volume far above anything needed .
2. Pump fills block ,pressure and flow equalizes through out block due to the excess flow provided from pump before hitting the head gasket restriction..
3. Coolant now flows through the entire length of head gasket that due to its design acts as the restriction regulating the total volume of coolant that will enter head and due to the excess flow volume available biases the flow to the larger number of holes along the exhaust side of the gasket compared to the number across the intake side of the gasket. Coolant does flow through all head gasket holes at same rate but more total volume flows through the exhaust side of head due to the larger number and size of the holes on the exhaust side of the head.
4.The coolant flow volume that is biased to the exhaust side of the head then flows basically up and over the combustion chambers (it does not flow rear to front along the head on the exhaust side of head) where it rejoins with the smaller coolant volume coming from the holes on the intake side of the head where it does now flow along the length of head to front discharge port entering the front manifold crossover to the thermostat.
5. Normally all flow discharges from head at front coolant outlet as there is no rear outlet. Adding a rear outlet will disrupt #4 flow. Depending on application the results may or may not be beneficial or necessary.
The head gasket functions as the flow and direction regulator.
fabr wrote: ↑Sat Dec 25, 2021 4:17 pm
What becomes obvious in these sbc coolant flow topics is that at least 99% of the posters have huge misconceptions as to how and where coolant flows through head/block.
Won't reread, but sure wouldn't say more then 9%, and definitely not 99!
Yes, water does flow down hill.
Only peeved at that flow too fast to cool tripe.
Good work OP, good luck.
Anyway, cant believe sometimes its the simple things that can't be understood and seem to go forever. ](./images/smilies/eusa_wall.gif "Brick wall"){kind=small}
Good luck and enjoy.
