What is with this???

You know what... my 351 in my Capri was like that, and I cut the restrictions out of the gaskets and never had an overheating problem with that motor even WFO at 100+.

I'd say match the gaskets to the holes in the block. What's the worst that happens, it runs too cold? Waaa... add fuel!
 
Extended Power said:
Why are these holes so SMALL????
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Its to mantain water pressure against the cylinder walls. The holes are small so that steem can pass through. That keeps the coolant pressurized against the cylinder instead of held away with a layer of steem.

did that make sense?$.02
 
That actually makes sense.
They must have had problems with the larger holes thus the redesign.
 
The picture is from the stock engine...it has never been touched, except for injector replacements.
This is why I questioned if I had the right "Up-dated" head gaskets....cuz they have the same little holes in them.

My truck is a August '03 build.

About the pressure statement: That is why I am changing to Evans coolant...it does not need ANY pressure to have an extremely high boil point.
And you are right...when the water starts to boil, it pushes away from the cylinders by making small bubbles. (Watch a pot on the stove...even thou a watched pot NEVER boils...) This creates even more heat, because the water isn't even against the cylinder walls anymore.

I thought the small holes were for retention time. Trying to slow down the flow in the heads to get better heat transfer.
My thoughts...it's retention time is WAAAAAAAAAAAAAY too much. I think that is why the heads lift. Can't push the water/steam through the small holes, and when it becomes mostly steam, which expands what...1800 times when boiled?? It will DEFINETLY lift the heads. JMO$.02
 
I think it's got more to do with emissions garbage than anything else. Keep it hot and it changes the exhaust properties.

You're not going to get enough steam pressure to lift the heads, it would push the water back through the water pump and everyplace else first. It's going to act evenly in all directions, and the first thing that will go boom is the tank, hoses and radiator, most likely in that order. But outside of that, there isn't anyone here, even the guys running twins, nox, propane, 500cc injectors that could generate enough instantaneous heat to cause that much damage from steam. Transfer function is all wrong. You'd need a couple thousand degrees in the cylinder to get that much heat to the other side, that quickly, and at that point, the piston won't be there anymore.

So back to the comment about the retention time, I agree it is too long. It is on most any engine today. They're designed for emissions not for performance or longevity. I'd cut those holes out and let it flow. If it becomes an issue, either change the thermostat to a higher temp, or put a slightly larger diameter fan/water pump pulley on, to under drive the pump and slow the flow rate down.

I seem to remember something about cylinder cavitation on the 6.9 engines that actually caused metallic erosion of the cylinder bores from the outside in. I forget how exactly this problem was dealt with later engines, other than an additive in the coolant.

If you're using this truck for work, and it's regularly being pushed and keeps itself warm, I think opening it up would be good. If it's a daily driver that sees the occasional blast, but never really works hard for more than 20-30 seconds on a launch, you might end up with problems related to not baking out the motor enough. aka grandma driving only to church on sundays... you know what that does to an engine...
 
Kleetus said:
I seem to remember something about cylinder cavitation on the 6.9 engines that actually caused metallic erosion of the cylinder bores from the outside in. I forget how exactly this problem was dealt with later engines, other than an additive in the coolant.
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A Jasper engines class I went to talked about the cavitation issue. They claimed it was in ALL diesel engines, but for some reason the 6.9L was bad, and the 6.0L was worse! They recommended using the additive, and changing the coolant quite often.
 
Another thing to look at...there are NO holes UNDER the exhaust ports of the heads. What this means is: the coolant is just sitting there...heating up with nowhere to go...
 
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Typical HG desiegn uses the restrictor holes for emissions. They are there to heat the engine faster when its cold. The largest contribution an engine makes to polution is done when it is cold.
 
I can only speek from my gas race engine eqperience. My dad has been a race engine builder for over 30 years. When we build 400 Chevys (known for poor cylinder cooling) into 406, 408, and 410 monster mouse engines, we change the cylinder heads to a 350 cast or aluminum head. In doing so, we drill a 1/8" hole in the blocked water port to allow for steam passage. This makes a DRASTIC cooling difference by mantaining pressure and allowing steam to escape.

I run one of these 406s in my Jeep with an additional 200hp NOS and never heat it up.

Now, yes alot of OEMs use temperature to control certain tuning aspects for emissions, but remember that diesels did not have to adhere until 07.5. Also, if you do cut the wholes out, and you experience boil over and can't get it to cool, changing you tstat will NOT help. It will change the temp that the tstat opens but will not mantain cylinder pressure. In our race engines we also run a restrictor plate with a 3/8 hole instead of a tstat. That is also to mantain cyl pressure.

Keep in mind, this experience is not with just drag or quick run engines, my dad is a sprint car/circle track engine builder. Our engines have to go 8-9000 rpm for hours. Cooling is something we have tested and retested.

Just my .50 $.02
 
HushpowerGuy said:
I can only speek from my gas race engine eqperience. My dad has been a race engine builder for over 30 years. When we build 400 Chevys (known for poor cylinder cooling) into 406, 408, and 410 monster mouse engines, we change the cylinder heads to a 350 cast or aluminum head. In doing so, we drill a 1/8" hole in the blocked water port to allow for steam passage. This makes a DRASTIC cooling difference by mantaining pressure and allowing steam to escape.

I run one of these 406s in my Jeep with an additional 200hp NOS and never heat it up.

Now, yes alot of OEMs use temperature to control certain tuning aspects for emissions, but remember that diesels did not have to adhere until 07.5. Also, if you do cut the wholes out, and you experience boil over and can't get it to cool, changing you tstat will NOT help. It will change the temp that the tstat opens but will not mantain cylinder pressure. In our race engines we also run a restrictor plate with a 3/8 hole instead of a tstat. That is also to mantain cyl pressure.

Keep in mind, this experience is not with just drag or quick run engines, my dad is a sprint car/circle track engine builder. Our engines have to go 8-9000 rpm for hours. Cooling is something we have tested and retested.

Just my .50 $.02
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Thanks!:Cheer:

I spoke with our mechanic here at work, who builds, and tunes race cars, he said that depending on how the coolant enters the heads plays a big role. If the coolant comes in the ends and flows past the tops of the chambers, it cools better than letting it drop down the cylinder walls. (Most of the heat is in the top section of the head/combustion chamber.)

So the small holes ARE there to limit the amount of coolant that enters the block.:rockwoot:
 
If it wasn't such a ***** to tear one of these down, I'd say cut the holes out, then run it for a while and see what it does. If it sucks, change out the gaskets.

I know diesels in general move a lot more coolant around than gassers, but from where to where and at what pressure I couldn't tell ya. I don't understand the cylinder pressure comment that's been made though... the total system pressure isn't going to change, if the cap's good for 20 psi (or whatever #) then regardless of holes or no holes, the water pressure around the bores is going to be no more than 20 psi. 20 PSI is a minimal pressure for boil reduction. I can see slowing the flow rate down to get some better heat transfer to a point, but too much makes the engine too hot (duh). Like I said before, and was mentioned above, it does stuff for emissions, and that generally hurts performance.
 
HushpowerGuy said:
I can only speek from my gas race engine eqperience. My dad has been a race engine builder for over 30 years. When we build 400 Chevys (known for poor cylinder cooling) into 406, 408, and 410 monster mouse engines, we change the cylinder heads to a 350 cast or aluminum head. In doing so, we drill a 1/8" hole in the blocked water port to allow for steam passage. This makes a DRASTIC cooling difference by mantaining pressure and allowing steam to escape.

I run one of these 406s in my Jeep with an additional 200hp NOS and never heat it up.

Now, yes alot of OEMs use temperature to control certain tuning aspects for emissions, but remember that diesels did not have to adhere until 07.5. Also, if you do cut the wholes out, and you experience boil over and can't get it to cool, changing you tstat will NOT help. It will change the temp that the tstat opens but will not mantain cylinder pressure. In our race engines we also run a restrictor plate with a 3/8 hole instead of a tstat. That is also to mantain cyl pressure.

Keep in mind, this experience is not with just drag or quick run engines, my dad is a sprint car/circle track engine builder. Our engines have to go 8-9000 rpm for hours. Cooling is something we have tested and retested.

Just my .50 $.02
Click to expand...

You're right about that, but an engine that runs at 8-9k has way different cooling characteristics than one that varies from idle to 4k with varying loads.

If and when mine goes boom which hopefully will never occur, I'll do it. I've done this with several other engines and haven't had any issues. Never tried it on a diesel though.
 
you need to run a bypass line out of the back of each head. The coolant gets airlocked at the top of the heads and forms steam pockets. When you pulled your old heads did you notice that there is rust build-up at the tops of the coolant passages? You can see the rust line in both rectangular coolant ports in the pic. I put 3/8x6an fittings in the back of the heads and plumbed it to my EGR bypass line.
 

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Yeah, I was going to do them in stainless steel 1/2" lines, and tie them in just under the thermostat housing.
 
im really curious to see how that works, and much it helps. Keep us updated!
 
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