Popped a freeze plug

[Broncobowsher]

The boss 302 block (and other aftermarket blocks with screw in plugs) was done for block rigidity.
Want to take the tangent of thin wall casting? The engine foundry hated making 427FE blocks. Very high scrap rates due to tight tolerances and core shift. Buick with the paper thin 455 blocks. They really pushed the thin wall casting,

 

[ntsqd]

All the while my long understanding of the reason for those holes in the side of the block has been for removal of the sand cores used in casting the block. Specifically the coolant jacket. Has/had nothing to do with freeze protection and everything to do with locating the cores used to create the coolant jacket and then allowing for the production removal of that sand.
Block rigidity is the common reason given for going to screw-in plugs, but in racing the screw-in plugs offer a level of robustness not matched by any of the more common plugs. Look in older books on building racing engines and one of the topics discussed will be using drive pins to mechanically retain those core plugs.

If you want numbers for coolant jacket pressure look up @nvrstuk 's thread about his testing of this. Real numbers from an experiment someone actual made rather than guesses and conjecture. With those numbers and the size of the core holes you can figure out just how much force is trying to eject those plugs and realize it's not a small number. The coolant jacket pressure is not caused by the radiator cap, but rather it is caused by the coolant pump.

I fell victim to exploding the heater core in the FSB. Hoses were replaced not realizing that there was a restrictor in the supply hose. So I made a new restrictor that fits into the inlet of the heater core.

 

[ba123]

All the while my long understanding of the reason for those holes in the side of the block has been for removal of the sand cores used in casting the block. Specifically the coolant jacket. Has/had nothing to do with freeze protection and everything to do with locating the cores used to create the coolant jacket and then allowing for the production removal of that sand.
Block rigidity is the common reason given for going to screw-in plugs, but in racing the screw-in plugs offer a level of robustness not matched by any of the more common plugs. Look in older books on building racing engines and one of the topics discussed will be using drive pins to mechanically retain those core plugs.

If you want numbers for coolant jacket pressure look up @nvrstuk 's thread about his testing of this. Real numbers from an experiment someone actual made rather than guesses and conjecture. With those numbers and the size of the core holes you can figure out just how much force is trying to eject those plugs and realize it's not a small number. The coolant jacket pressure is not caused by the radiator cap, but rather it is caused by the coolant pump.

I fell victim to exploding the heater core in the FSB. Hoses were replaced not realizing that there was a restrictor in the supply hose. So I made a new restrictor that fits into the inlet of the heater core.

I think you mean coolant temp. This was the start of this uptick in discussion. The coolant pump doesn't cause pressure, it just circulates the coolant. If the engine stayed cool, no pressure would build coolant pump or not. Remove the belt and you're still going to have a pressure build up in your system. It'll just not be even all the way around and it won't cool.

 

[ntsqd]

No, the coolant pump is the main source of pressure in the coolant system (1.5X - 2x+ the cap pressure). IF there is either a t-stat or a restrictor in the system. Without either of those you will have no block pressure. Cap pressure raises the coolant's boiling point in the whole system, block pressure raises the coolant's boiling point in the coolant jacket where all of the hot spots are. Cap pressure is not high enough to keep the coolant from flash boiling at those hot spots and is why running without either a t-stat or a restrictor usually results in over-heating.

Early farm implement engines used a thermocline coolant circulation system that had no pump. The hot water expanded and moved towards the top of the system pulling the cool water in at the bottom. They did cool and circulate the coolant without a pump, but those were not high output for their displacement engines. There will be circulation without the coolant pump working, it just won't be anything close to enough exchange to keep a modern engine cool.

 

[ba123]

No, the coolant pump is the main source of pressure in the coolant system (1.5X - 2x+ the cap pressure). IF there is either a t-stat or a restrictor in the system. Without either of those you will have no block pressure. Cap pressure raises the coolant's boiling point in the whole system, block pressure raises the coolant's boiling point in the coolant jacket where all of the hot spots are. Cap pressure is not high enough to keep the coolant from flash boiling at those hot spots and is why running without either a t-stat or a restrictor usually results in over-heating.

Early farm implement engines used a thermocline coolant circulation system that had no pump. The hot water expanded and moved towards the top of the system pulling the cool water in at the bottom. They did cool and circulate the coolant without a pump, but those were not high output for their displacement engines. There will be circulation without the coolant pump working, it just won't be anything close to enough exchange to keep a modern engine cool.

Yeah, I disagree and can prove it by simply starting the engine with the cap off. It won’t go anywhere. Doesn’t overflow, even without a tstat, it’ll just flow.

Add heat to it and bam.

 

[ntsqd]

What won't go anywhere? What is it that you think you're proving by running without a cap? Have you looked up Brian's thread on coolant pressure?

 

[jamesroney]

I think you mean coolant temp. This was the start of this uptick in discussion. The coolant pump doesn't cause pressure, it just circulates the coolant. If the engine stayed cool, no pressure would build coolant pump or not. Remove the belt and you're still going to have a pressure build up in your system. It'll just not be even all the way around and it won't cool.

Whoa now...

The coolant pump absolutely creates pressure. And not just a little bit. The water pump impeller creates pressure in proportion to rpm. While it is true that a car idling with an open radiator does not show the 3-4 psi difference, a Trans-Am car at 7500 RPM will push 50 psi against whatever pushes against it. Usually it's the thermostat, or the fixed orifice restrictor. Or the head gasket ports, or the radiator itself. Keep in mind that the pressure rise an increase. So if you pressurize the whole cooling system, the pump can add 50 psi more.

The high sustained RPM water pump pressure is why the SideOiler 427 got the screw in freeze plugs. Same thing for the Boss 302. To claim that a block is more rigid because you tighten a tapered threaded plug in it defies physics. The high RPM, high endurance engines got threaded plugs to keep them from popping out at 60 psi. And yeah, it will 100% blow up a heater core. The SCCA Trans-Am guys actually "strapped" their core plugs to keep them from self-extracting. Bud Moore, Donohue, and Penske acknowledge that they trimmed the vanes and the Z-28 got special underdrive pulleys.

The beauty of water pumps is that they can only build pressure if you push back against them. Otherwise, they just move water. Every block, head, water jacket, thermostat, and radiator core "pushes back."

"main source of pressure" is kinda vague. The "main source" of pressure in the radiator is the expansion of the coolant. (about 12 oz) and the partial pressure of vapor at 200 degrees, and the expansion of any air pockets in the system. But the water pump pushes about 5 psi harder than the inlet pressure at idle. Jack that up to 7500 rpm and that pump will push 60 psi no problem.

 

[ntsqd]

A pump can't build pressure without some kind of restriction to flow in the system. Flow, pressure, and the size of the restriction are all tied together, varying any one of them changes at least one of the others.

My "main source of pressure" comment was specifically aimed at the operating pressure in the coolant jacket, that being the portion of the whole system that is between the pump and the t-stat or restrictor. At anything much more than idle the pump generates as much or more pressure than the thermal expansion (i.e. cap pressure) does.

And that may be the part that isn't understood, that between the pump and the t-stat/restrictor the coolant pressure can easily exceed the cap pressure depending on the pump's impeller RPM. At idle when warm the whole system is at least at cap pressure, but the coolant jacket will be at little higher pressure and at high RPM the coolant jacket pressure will be far higher than the cap pressure.

 

[jamesroney]

My "main source of pressure" comment was specifically aimed at the operating pressure in the coolant jacket, that being the portion of the whole system that is between the pump and the t-stat or restrictor. At anything much more than idle the pump generates as much or more pressure than the thermal expansion (i.e. cap pressure) does.

And that may be the part that isn't understood, that between the pump and the t-stat/restrictor the coolant pressure can easily exceed the cap pressure depending on the pump's impeller RPM. At idle when warm the whole system is at least at cap pressure, but the coolant jacket will be at little higher pressure and at high RPM the coolant jacket pressure will be far higher than the cap pressure.

As usual, we agree…

 

[ntsqd]

Sometimes violently, but yes.

 

[ba123]

I still say that's flow pressure and not system pressure. It's rare I argue with you James, but if you turn the engine off, does the pressure go away?

Engine running, and hot, squeeze that top radiator hose, then turn the engine off and squeeze it again. It is any easier to squeeze?

 

[ntsqd]

I still don't understand your position.

Pressure is pressure, regardless of the source. Multiple sources are not additive, can not have two 5 psi sources and get 10 psi, you still have 5 psi. If thermal expansion results in 5psi and the pump is putting out 10 psi then system pressure is 10 psi while the pump is running and 5 psi when it is not, so long as the coolant is still at the temperature that produces 5psi.

 

[DirtDonk]

The top hose is outside of the pressure producing area.
It’s not between the pump and the restriction.

And yes, when you turn the engine off the pump pressure goes to zero.

Leaving the cap off does not change circulation, or pressure between the pump and restriction.
It does, however, remove the pressure created by temperature. What I previously called ambient pressure or temperature. Whatever term/phrase it was, I used.
Lowering the boiling point among other things.

 

[jamesroney]

I still say that's flow pressure and not system pressure. It's rare I argue with you James, but if you turn the engine off, does the pressure go away?

Engine running, and hot, squeeze that top radiator hose, then turn the engine off and squeeze it again. It is any easier to squeeze?

You can argue all you want. You know I don't mind.

We are talking about different pressure measured in different places. The upper radiator hose is an easy place to measure what you are calling "system pressure" And no, that pressure is generally the result of thermal expansion from the heated coolant / vapor pressure / air pockets and doesn't care if you have a water pump turning or not. We know that the expansion pressure does not go away.

(...BUT if the radiator core is the pressure "restriction" then the upper hose will indeed go higher pressure with increased water pump flow.)

So it all depends on where the restriction sits. And there has to be a restriction, or else you cannot build pump pressure. USUALLY it is in the thermostat orifice. So everything behind the thermostat sees increased pressure due to coolant flow. But if you look at a 302 head gasket, ALL of the coolant flows thru those 2 little triangle holes in the rear of the head gasket. So there is no such thing as "the pressure..." There are many pressures. As the temperature rises, the pressure everywhere goes up by that 7-12 psi number. But the pressure between the water pump discharge and the thermostat goes up by the flow curve of the impeller PLUS that 7-12 psi. It's just hard to measure that pressure, because it exists in the block, then the heads, then the intake, and never makes it past the thermostat. (and by thermostat, I mean the orifice. And if you leave the thermostat out, we all know that the 7-12 psi still happens.) But the 60 psi is harder to achieve, and needs to push against the radiator core tubes. Regardless, the core plugs see the sum of the expansion pressure, and the pump pressure.

I can turn on my Bronco, and once it achieves steady state at 190 degrees, I can remove the radiator cap and just watch the coolant flow thru the radiator. "system pressure" is 0 psig. But I will guarantee you that the pump is making pressure in the block. It's just all gone by the time I see it in the radiator. Same exact thing happens in my boat. I pull water from the lake. I put the same water back in the lake. My lake sits at 0 psi. But my water pump makes pressure in the block. And if I wind it up to 8,000 PRM with a thermostat in it, it will blow out the freeze plugs that aren't freeze plugs.

 

[ba123]

Ah, yeah, we're talking about totally different things.

Totally agree and thanks for the clarification. Thought I might be going crazy.

 

[jamesroney]

Ah, yeah, we're talking about totally different things.

Totally agree and thanks for the clarification. Thought I might be going crazy.

Did you ever get any dyno numbers on that Intake? Still wondering if the view was worth the climb...

 

[Steve83]

The coolant pump doesn't cause pressure, it just circulates the coolant.

A pump creats FLOW. Blocking/restricting that flow increases the pressure to a degree relative to the amount of restriction. And all flow has restriction due to friction against the container surfaces & against the fluid being slowed by that friction. But a thermostat forcing the majority of the flow to go through the heater core &/or the bypass hose causes a substantial restriction.

If the engine stayed cool, no pressure would build coolant pump or not.

No pressure would build BEYOND the last significant restriction. But there would be flow-generated pressure between the pump & the last significant restrictions (the heater core on its branch, and the bypass hose on that branch). To judge if a restriction is significant for the flow, simply look at the cross-sectional area of the pump outputs (the journals passing through the timing cover) and compare that total to those of the heater core outlet nipple plus the inside bore of the bypass nipple on the t'stat cover. If you're considering when the t'stat is open, add the area of its opening.

Remove the belt and you're still going to have a pressure build up in your system. It'll just not be even all the way around...

Without a flow-generator, or substantial convection flow (thermocline), the pressure at any point of a particular depth will be exactly the same as any other point at that depth; IOW: VERY even all the way around.

...in the FSB. ...there was a restrictor in the supply hose.

Ford never put a restriction anywhere in an '80-96 Bronco or gas F-series. Was yours a '78-79? I'm not nearly as familiar with those.

Cap pressure is not high enough to keep the coolant from flash boiling at those hot spots and is why running without either a t-stat or a restrictor usually results in over-heating.

This doesn't stand up. Assuming it was correct and the pump & t/stat were working perfectly with properly-mixed coolant; the coolant would get hotTER than enough to flash-boil at cap pressure, but it wouldn't because of the restriction. And then at the moment that super-heated coolant passed the restrictions (heater core, t'stat, & bypass hose), it WOULD flash-boil, just like refrigerant passing the orifice tube/expansion valve in the A/C system. But the coolant system has no accumulator to allow for boiling, so it would immediately over-pressure the cap. But we know that doesn't happen, so it also wouldn't happen without the restriction. If there's enough properly-mixed coolant flowing and enough radiator & fan to dissipate the engine heat, then the engine will never get hot enough to boil the coolant regardless of a thermostat. The cast metal cylinder walls & heads will slow the combustion heat loss so that the coolant sides never get that hot, and most of the heat will go out the exhaust, like it should.

...by simply starting the engine with the cap off. It won’t go anywhere. Doesn’t overflow...

All of mine will. As the engine warms up, the little air pockets throughout the system get hot & expand, pushing coolant out the radiator neck.

The "main source" of pressure in the radiator is the expansion of the coolant. (about 12 oz)...

What about the expansion of the block, hoses, heater core, & radiator going from 80-200°F? I haven't tried to calculate or measure them, but I bet they're significant.

... the partial pressure of vapor at 200 degrees, and the expansion of any air pockets in the system.

This is the source of the system pressure, assuming there's a cap & no substantial leak.

...if you turn the engine off, does the pressure go away?
Engine running, and hot, squeeze that top radiator hose...

The flow pressure inside the block & heads goes away, leaving only the system (temperature-caused) pressure. The radiator hoses don't contain any flow pressure because they're on the return side of the pump's flow, after the restrictions. It's vaguely like the difference between the PS high-pressure hose (being analogous to the engine block) and its return hose (being analogous to the radiator & its hoses).

 

[ba123]

Did you ever get any dyno numbers on that Intake? Still wondering if the view was worth the climb...

I've wasted all my energy chasing other things... First it was the loud exhaust, got rid of the Magnaflow that hurt my ears, then it seems the Flowmaster I love creates too much heat, trans gets too hot when I'm really hard on it, been working on that and once I'm happy, I need to change a couple things in the exhaust and when I can be as hard as I need to on it, then I can spend a little more time tuning the full out and then get it on a dyno.

Either way, I know I've gotten at least something out of this intake in addition tot he looks. I can pop the hood and just stare at it and I'm happy. Although despite moving the engine forward, the torque of the engine moving does make it at least rub the firewall a little (noticed a spot when I put my catch can for my trans breather the other day).

 

[EPB72]

I still say that's flow pressure and not system pressure. It's rare I argue with you James, but if you turn the engine off, does the pressure go away?

Engine running, and hot, squeeze that top radiator hose, then turn the engine off and squeeze it again. It is any easier to squeeze?

So here is an example .
servicing a BMW with and electric waterpump volvos as well ,, when refilling cooling system You need to put vehicle in bleed mode or use scan tool to do the same thing basicly your running running the pump with the engine off. the cycle can take upto 15 minutes. you can repeat as well ,, on Bmw your supposed to have cap installed , whendone ther is no pressure built up .

there is pressure behind restrictions in the system though as there is cylinder head to expansion tank return for removing trapped air . that return flow is like someone putting there finger over the end of a garden hose , thats why you put the cap back on or you;ll make a mess ,,

another thing that happens vehicle at operating temp driven on test drive return to service bay. system is pressurized , just so happen have scan tool on and monitoring coolant temp, lets say 212 *F wait a minute upto 217* fans cycle on and drop temp down 193*f .. or so when fan cycles off ,, feel upper hose and pressure drops off to almost nothing , not alwasys but pretty common,

 

[jamesroney]

What about the expansion of the block, hoses, heater core, & radiator going from 80-200°F? I haven't tried to calculate or measure them, but I bet they're significant.

As it turns out, they are not. I started doing the Alpha delta T calculations (gross estimates) on the cast iron block, and concluded that a 100 degree temperature rise yields a volumetric capacity increase of about a thimble. AND, it turns out that most of that expansion goes the wrong way. Because the block, hoses, radiator, and heater define the "container" any expansion of those items increases volume. The block gets bigger. (which reduces pressure.)

Then I thought about the fact that it's a cavity, and the inside of the block gets bigger too. But since the outside of the block is bigger than the inside of the block, getting it hotter makes the bigger part bigger while the small part gets bigger. Then I considered that the heat comes from the cylinders, which makes the inside of the block hotter than the outside of the block. Which makes the cavity smaller. But I already assumed that the cylinder was at steady state, and I already chose to ignore boundary effects. So I convinced myself that I am right. Then I realized that I was satisfied that I was right, and did not need to go further. Then I considered small combustion leaks, and cast iron permeation and cavitation and stopped.

So yes, 2 gallons of 50/50 glycol water will expand about 12 oz with a 100F temp rise. So you will to displace about a coke can of liquid.

I will freely admit that I let AI do the math, and I did not validate the results, because directionally they are backwards. (the container volume actually grows)

...But I did think about it.