• Hello Guest, welcome to the initial stages of our new platform!
    You can find some additional information about where we are in the process of migrating the board and setting up our new software here

    Thank you for being a part of our community!

Cooling system changes for high rpm use.

Probably good evidence to add to the case here. There are alot of other forces on the block besides the pressure inside from hot water. The twisting and bending loads on the side of the block near the motor mount come to mind. And in my case, the freeze plugs I have had trouble with are near the motor mount bolt holes. Jiggling, twisting, pressure inside. It probably all contributes. And maybe all that is more important than cavitation or some water flow related issue like I originally was thinking.

i'm reading this post in Z and im asking question about over pressure possibility at high RPM....anyone have take a pressure gauge and do a inrun high rpm pressure test ??
i have tested my block at 100 psi air pressure (checking for crack) and never pop a frost plug ?? so the question is if the pressure raise up to 100 psi in block at 7200rpm or more !
 
Probably good evidence to add to the case here. There are alot of other forces on the block besides the pressure inside from hot water. The twisting and bending loads on the side of the block near the motor mount come to mind. And in my case, the freeze plugs I have had trouble with are near the motor mount bolt holes. Jiggling, twisting, pressure inside. It probably all contributes. And maybe all that is more important than cavitation or some water flow related issue like I originally was thinking.

yeah its possible to engine force at bottom around engine support will allow more twist than my relaxe pressure test on my work table...so in b21 its a not the same frost plug than the b230 any people test this at high rpm ??
 
Quote:
Originally Posted by Dave_242gt
i'm reading this post in Z and im asking question about over pressure possibility at high RPM....anyone have take a pressure gauge and do a inrun high rpm pressure test ??
i have tested my block at 100 psi air pressure (checking for crack) and never pop a frost plug ?? so the question is if the pressure raise up to 100 psi in block at 7200rpm or more !

__________________

The overflow tank's cap has a pressure relief valve that hold the radiator's pressure at a constant amount. Just a few pounds is all that is required. So IMO that blows the excessive pressure idea all to hell, as long as cap is working correctly.
 
I used a laser temp gun to check temperature when I tried out the new cooling system on my boat.
I was finding 148-155* at the front of the engine and ~170* at the rear. It's obvious that the back of engine gets cheated out of some cooling. Having the heater on, allowing some coolant to exit the rear of engine and promote more rearward flow, would-in theory-even it out. I wonder if you guys making big power are seeing stagnant coolant boiling in the rear of the engine and causing the localized pressure. Along with some block squirm, both issues together could be forcing the plugs out.
 
The overflow tank's cap has a pressure relief valve that hold the radiator's pressure at a constant amount. Just a few pounds is all that is required. So IMO that blows the excessive pressure idea all to hell, as long as cap is working correctly.

The pressure and temperature is not even in the entire system. It's kind of like high and low pressure areas in the Earth's atmosphere.
 
The pressure and temperature is not even in the entire system. It's kind of like high and low pressure areas in the Earth's atmosphere.
It's all vented in the same place though isn't it? There is only about 5 lbs pressure in the coolant system on a Volvo. American cars in the1960-80s ran more coolant system pressure , some up to 15 psi, and nowadays more than that. They never "blew" freeze plugs. It'll take more than 5-20 psi to unseat a freeze plug.

Some need to realize that above 15-20 boost, is more than these engines were intended to do without some other mods. Screw in freeze plug would be one of these IMO.
 
Last edited:
Some more food for thought... I've seen/heard of freeze plugs coming out in b21FTs that are nearly stock, with maybe raised boost but not necessarily much else. I can't remember if those were previously replaced freeze plugs or not though. Still, something, aside from super power levels can also have an effect on plugs popping out.
 
Yeah, if the water in blocck freezes or the wrong size plug is installed. I've owned a LOT of b21s & B230, have one with over 500,000 on it. Freeze plugs still in it.
 
It's all vented in the same place though isn't it? There is only about 5 lbs pressure in the coolant system on a Volvo. American cars in the1960-80s ran more coolant system pressure , some up to 15 psi, and nowadays more than that. They never "blew" freeze plugs. It'll take more than 5-20 psi to unseat a freeze plug.

Some need to realize that above 15-20 boost, is more than these engines were intended to do without some other mods. Screw in freeze plug would be one of these IMO.
If you notice from a previous post i made here, i dont think these freeze plugs blowing out should be happening, of course.

But my point is, there's going to be locally occuring high pressure spots in the water passages in the block. They probably dont last very long, but they happen. Just like the water isnt 200 degrees in the whole block. It's all vented in one place, and thats exactly why high pressure spots can occur. The pressure has to work its way back to the overflow bottle...which probably occurs pretty quickly.
 
The water is under pressure right? Do yo really think that little bit of localized hotter water is standing still? No it's being piushed around by the pump.

It has a water pump, remember?
Tell ya what. take a block, seal up all water outlets/inlets. Pressurize it with 120PSI air pressure. See if plugs pop out. Or read this thread where someone already did this.
 
The water is under pressure right? Do yo really think that little bit of localized hotter water is standing still? No it's being piushed around by the pump.

It has a water pump, remember?
Tell ya what. take a block, seal up all water outlets/inlets. Pressurize it with 120PSI air pressure. See if plugs pop out. Or read this thread where someone already did this.

I'm not the one that has ever had a freeze plug pop out, remember? No interest.

And no, the water is not standing still. And thats why the persure will never be 5 psi in the whole system. That hotter water moves into the radiator...and what replaces it? More water, which quickly becomes hotter....
 
Oh, and yeah...my conclusions from this thread are pretty much that this is caused by block squirm...
Maybe that and poor installation or low quality plugs being used. I've had friends with cars putting out not even 200whp who've had their's pop out.
 
And no, the water is not standing still. And thats why the persure will never be 5 psi in the whole system. That hotter water moves into the radiator...and what replaces it? More water, which quickly becomes hotter
LOL, you need to read upon how cooling systems work.

Block squirm is most likely the culprit on popping freeze plugs. That & wrong size plugs installed by machine shop, which has been covered in Maint section.
 
LOL, you need to read upon how cooling systems work.

Block squirm is most likely the culprit on popping freeze plugs. That & wrong size plugs installed by machine shop, which has been covered in Maint section.


Sounds like you need to read upon how cooling systems work. To think that one vent in one place is going to keep the system the perfect pressure in the entire system is insanity.
 
That is what the pressure release cap does. BTW, at first you said it was water pressure that forced the plugs out. then you say it's the block squirm. now you think there is more pressure in the cooling system than the cap allows for.


Don't you find it strange that American V8s with 2-3 times the cooling system pressure of a B20-b230 do not blow freeze plugs out?

Also, freeze plugs are design to come out if the water in block freezes & expands. If it takes that amount of pressure to unseat one, it seems to me 4-5 psi sure isn't going to do it.

Sure there are 'hot spots" in the block's water passages., most of them are in the cylinder head, and around the block at/near combustion chambers. The freeze plugs are not really all that close to these areas.
 
That is what the pressure release cap does. BTW, at first you said it was water pressure that forced the plugs out. then you say it's the block squirm. now you think there is more pressure in the cooling system than the cap allows for.


Don't you find it strange that American V8s with 2-3 times the cooling system pressure of a B20-b230 do not blow freeze plugs out?

Also, freeze plugs are design to come out if the water in block freezes & expands. If it takes that amount of pressure to unseat one, it seems to me 4-5 psi sure isn't going to do it.

Sure there are 'hot spots" in the block's water passages., most of them are in the cylinder head, and around the block at/near combustion chambers. The freeze plugs are not really all that close to these areas.

You don't even have a clue who you're talking to.
 
I'm sure you both know exactly who you're talking to, this is the internet. :roll:
 
I'm sure you both know exactly who you're talking to, this is the internet. :roll:

haha....my point is, he's trying to argue with me about something i agree with him on, and have agreed with him on the entire time...I dont know why he thinks i said high pressure was pushing freeze plugs out. I just know that the system is not the same pressure at all points...its obvious. I never said it was enough to push freeze plugs out.

My dad used to have a v8 with 500 horsepower.....never had a freeze plug come out.

Infact....I've seen people have engines with water in them freeze, and not push the freeze plugs out.
 
Back
Top