Head Gasket Question

[SyntheticShield]

When I pulled one of the heads off my engine, I noticed with the OEM head gasket that where the water jacket ports are, there was just a small hole drilled rather than having the full opening.

Can anyone tell me why this is? Can that be opened up to the full size of the opening?

[chrisb]

ive noticed this too, i wonder if this is the same on the mls head gaskets too? now i wouldnt see why you couldnt open them up to the size of ports. maybe they only make one style of gasket to fit over all the years, cause i kno there were slight improvments on the heads 99 and up.

[Zef_66]

It is my understanding that these ports need to be restricted so that the coolant stays in contact with the hot parts of the engine in order to cool properly. Very much like why you don't want to run without a thermostat.

In order for heat to be transferred from the hot cylinder walls to the cool coolant, the coolant needs to remain in contact with the hot walls for a certain amount of time. The cooling system is designed with restrictions in place for this contact to take place, and thus the desired amount of cooling.

Again, this is just my understanding, so take it FWIW. But I would just leave the head gaskets as they are.

[beastin1]

It is my understanding that these ports need to be restricted so that the coolant stays in contact with the hot parts of the engine in order to cool properly. Very much like why you don't want to run without a thermostat.

In order for heat to be transferred from the hot cylinder walls to the cool coolant, the coolant needs to remain in contact with the hot walls for a certain amount of time. The cooling system is designed with restrictions in place for this contact to take place, and thus the desired amount of cooling.

Again, this is just my understanding, so take it FWIW. But I would just leave the head gaskets as they are.

that does make sense.....

[SyntheticShield]

I had thought about the fluid dynamics aspect of it, and I was afraid that is what someone was going to point out. Its not like our engines have a tendency to overheat for no reason or due to some engineering flaw, but I would wonder if it would benefit from opening up that hole just a little. Perhaps not to the full size but just so you would have a little more flow

There is a LOT of room in there for coolant around the cylinders. Or perhaps even better, with the restrictions in the front exhaust manifold, if there would be any benefit to modifying the front head gasket only?

[GR8racingfool]

I would leave them be, stock or after market.

It is my understanding that these ports need to be restricted so that the coolant stays in contact with the hot parts of the engine in order to cool properly

as to why, you are correct. Small holes = resistance, which is good.

~F~

[Zef_66]

I had thought about the fluid dynamics aspect of it, and I was afraid that is what someone was going to point out. Its not like our engines have a tendency to overheat for no reason or due to some engineering flaw, but I would wonder if it would benefit from opening up that hole just a little. Perhaps not to the full size but just so you would have a little more flow

There is a LOT of room in there for coolant around the cylinders. Or perhaps even better, with the restrictions in the front exhaust manifold, if there would be any benefit to modifying the front head gasket only?

On a modded engine that is going to be raced, you might gain something by opening them up a little. But how much? I don't know. And I doubt you know for sure.

But I do know that GM tested these kinds of things. Their engineers are smarter than I am. And like you said, these engines don't have issues with overheating. Only when there are issues elsewhere in the cooling system from bad parts or lack of maintenance is overheating a problem. Even then, opening these holes up will only cover up the problem that needs fixed.

I wonder what people like ZZP do on their race engines?

[SyntheticShield]

Zef, I agree with your statement, but Im going to contend with you on a particular statement cause it just irks me and I know you are one person that can be discussed and debated with without it getting out of control.

Yes, GM probably tested these things, and I will never say a person is smarter than I because I wont limit myself that way. What they do have is more specific training than I but they dont know anything that I could not learn nor could I do without that same training and experience.

That said, the issue I have (albeit maybe a small one in most peoples eyes) is that a car rolls off the assembly line, in 99% of the cases, set up to work across the widest possible customer base. That is to say that it is designed and built with a few specific goals in mind but targeted to the widest possible consumer base. In other words, they hope that maybe one shortcoming in one area to a person will be made up for buy several other things that a particular person likes. Its a balancing act.

Secondly, the vehicle the comes off the line is first designed and built to meet existing legistlation (read: emissions and pollution standards), then to meet performance and comfort goals then reasonable longevity standards.

So what is the point to all this? The point is that when a design is settled on and put into production, its not a design that had being the best at its core, or being the most durable, or anything like that. Rather the design is centered around whether or not it will 'adequately' perform and meet requirements. And adequately sometimes does not even meet the middle of the road in overall performance.

So with all that in mind, I circle back to what you stated and say yeah, you are probably right. If I were to modify that opening, what would I gain, what do I hope to achieve or what will it improve? It would be good to know just what exactly does ZZP, Intense or any of the other dedicated race teams do.

But I do know this and I am VERY confident in stating, there is likely room for improvement in that design. Whether or not it will result in any noticeable or significant gains or even if they are worth persuing remains a question to be answered.

However, its not meant as an attack on you in any way. I just dislike that statement to an extent as it assumes that the GM engineers had the best performing product in mind when that part, that engine, that car was built and that is not the case. I dont view the engineers with contempt in anyway, but having worked with a few over the years and the compromises required to meet imposed deadlines and cost controls I understand the process.

Furthermore I have never held the concept that just because one has a degree or specialized training means they are in anyway better than I or smarter. They are more likely to have the solution because they see and understand things in a larger more global view of the subject matter but it doesnt exclude anyone from coming up with a solution that they did not think of or consider.

[Zef_66]

Zef, I agree with your statement, but Im going to contend with you on a particular statement cause it just irks me and I know you are one person that can be discussed and debated with without it getting out of control.

Yes, GM probably tested these things, and I will never say a person is smarter than I because I wont limit myself that way. What they do have is more specific training than I but they dont know anything that I could not learn nor could I do without that same training and experience.

That said, the issue I have (albeit maybe a small one in most peoples eyes) is that a car rolls off the assembly line, in 99% of the cases, set up to work across the widest possible customer base. That is to say that it is designed and built with a few specific goals in mind but targeted to the widest possible consumer base. In other words, they hope that maybe one shortcoming in one area to a person will be made up for buy several other things that a particular person likes. Its a balancing act.

Secondly, the vehicle the comes off the line is first designed and built to meet existing legistlation (read: emissions and pollution standards), then to meet performance and comfort goals then reasonable longevity standards.

So what is the point to all this? The point is that when a design is settled on and put into production, its not a design that had being the best at its core, or being the most durable, or anything like that. Rather the design is centered around whether or not it will 'adequately' perform and meet requirements. And adequately sometimes does not even meet the middle of the road in overall performance.

So with all that in mind, I circle back to what you stated and say yeah, you are probably right. If I were to modify that opening, what would I gain, what do I hope to achieve or what will it improve? It would be good to know just what exactly does ZZP, Intense or any of the other dedicated race teams do.

But I do know this and I am VERY confident in stating, there is likely room for improvement in that design. Whether or not it will result in any noticeable or significant gains or even if they are worth persuing remains a question to be answered.

However, its not meant as an attack on you in any way. I just dislike that statement to an extent as it assumes that the GM engineers had the best performing product in mind when that part, that engine, that car was built and that is not the case. I dont view the engineers with contempt in anyway, but having worked with a few over the years and the compromises required to meet imposed deadlines and cost controls I understand the process.

Furthermore I have never held the concept that just because one has a degree or specialized training means they are in anyway better than I or smarter. They are more likely to have the solution because they see and understand things in a larger more global view of the subject matter but it doesnt exclude anyone from coming up with a solution that they did not think of or consider.

Scotty, I agree with you 100% about the factors that are involved with producing a car. Having talked to a few GM engineering, I know the performance things they can do to a car, but are not allowed to put into production due to many of the factors that you mention. And I also agree that people use the intelligence of the engineering as a point not to mod anything sometimes, and I hate it as well.

But I said that based on this situation alone. The basic 3.8 litre engine that we have in our cars was originally designed in early 1970s. Millions of these engines were made. Little was changed in the way of the cooling system of the engine itself. While I don't have hard facts of this, I am sure that this cooling system was tested through the years. So 30 years later, I would assume it would be very well established as a working system in all cars.

Now, like you mention there are trade-offs. But I don't see any of those trade-offs being much to play into the cooling system design of an already existing engine. And I can see no reason why, through the testing of this engine and cooling system, would they not want to use the best performing head gasket design. Sure, there may be trade offs to use existing gaskets, or compatibility of parts. But for the most part, the size of a hole would be a very minor change that is relatively cheap to make. Again, I can see no reason why GM wouldn't use the best performing head gasket for the cooling system, and in this instance.

And again, I do think that the head gasket design is best for the engines GM produces in the platforms they install them in. And like many, many other things, this may be not be correct for every application of the engine, especially aftermarket. But for the majority of the people here and on this board, I think I can safely say that no modification to the head gasket is needed. I did mention ZZP race team and wonder what they, and other teams similar to them do. But again, this is a very specialized application that many of us will not even come close to. My guess is 99.99% of the people who are going to use head gaskets and install a set of heads will not see any noticeable gains in cooling by modifying the head gaskets over stock.

But I do agree with you 100% that the catch-all statement of "GM Engineers know best!" is totally wrong in a lot of cases. And most of the time I hate when people use it. But I think for this specific situation, it is a pretty good assessment and explanation.

Also, just to touch on the statement about the GM engineers are smarter than I. I didn't mean that in a houlier than thou attitude that I think it came off as. I just meant that I have not studied, researched, or worked in these areas. I have taken fluid dynamics, and thermodynamics classes. But I have not focuses at all on these topics (not to mention they were years ago.) I do agree that a title or degree does not make someone an expert in a field. I have met many older engineers that never attended college, don't have a degree, but have so much knowledge and understanding of things it is amazing. I have also met people who don't work in any kind of engineering or technical field, but have an awesome way of thinking about things and coming up with new ideas and thoughts outside the box, even with mechanical things. But my statement was simply to make a point that GM does extensive testing, spends millions of dollar on R&D, and has some pretty smart people working for them. Again, not saying anyone is above anyone else. And not saying that GM designs are perfect. But as mentioned above, in this situation, it is better to leave the head gaskets alone.

[SyntheticShield]

Zef, I'll agree with your statement as well, I think we are on the same page, I just like tinkering and know there is a margin to be played with in just about anything to do with cars. But I think in this application I will have to defer to keeping the status quo because it is true that with the millions (I read somewhere on the order of 20 million) that have been produced, surely refinements have crept in that made it the reliable engine that it is. I dont know if I mentioned it, but I have 116k on that engine, have run synthetics in it since around 40k? or so and I can still see the honing cross hatch marks in the bores.

Also, I did not mean to come across that I took your statement about GM engineers as a holier than thou statement and Im sorry if I gave you the impression thats how I took it. I meant simply to point out that I am not intimidated by degrees, studies or experience. I bow to no one, no degree, no titles, etc. I respect them, but I dont roll over and play dead because of them. I may take a stance of silence if I feel my understanding is inadequate but thats not to be taken as a lack of confidence, intimidation or anything like that, Im just using wisdom to know when it might be best I kept my mouth shut.

Anyway, thanks for your input. One of these days we'll get to meet and I look forward to what I know is going to be a memorable conversation about many things.

[Zef_66]

Zef, I'll agree with your statement as well, I think we are on the same page, I just like tinkering and know there is a margin to be played with in just about anything to do with cars. But I think in this application I will have to defer to keeping the status quo because it is true that with the millions (I read somewhere on the order of 20 million) that have been produced, surely refinements have crept in that made it the reliable engine that it is. I dont know if I mentioned it, but I have 116k on that engine, have run synthetics in it since around 40k? or so and I can still see the honing cross hatch marks in the bores.

Also, I did not mean to come across that I took your statement about GM engineers as a holier than thou statement and Im sorry if I gave you the impression thats how I took it. I meant simply to point out that I am not intimidated by degrees, studies or experience. I bow to no one, no degree, no titles, etc. I respect them, but I dont roll over and play dead because of them. I may take a stance of silence if I feel my understanding is inadequate but thats not to be taken as a lack of confidence, intimidation or anything like that, Im just using wisdom to know when it might be best I kept my mouth shut.

Anyway, thanks for your input. One of these days we'll get to meet and I look forward to what I know is going to be a memorable conversation about many things.

Scotty,

Glad you see it my way.

But really, I often times think about things and ask questions, even though I don't have the intent to do so. Asking questions is how you learn. And I have asked many, many questions, and continue to do so.

But the houiler than thou part. I didn't necessarily mean you took it that way. I just went back and read what I wrote. And re-reading it, I could see how some could think I meant it that way. And just wanted to make sure you didn't take it that way. No biggie.

And the wife and I are planning a round the nation trip next year. Maybe I will schedule a stock in OK.

[SyntheticShield]

And the wife and I are planning a round the nation trip next year. Maybe I will schedule a stock in OK.

I'll be eagerly waiting.

[gixer2000]

ill bet they are restricted because the slower you move the coolant through the heads the more heat it will absorb. if it goes to fast it wont asorb enough and then we have a problem. If it moves to slow it would run hotter

[SyntheticShield]

Yeah, I think that is the general consensus. If it were a naturally aspirated motor, I would slow it down some more cause that heat helps vaporize the fuel better, but in a supercharged application you have to contend with KR a bit more so it becomes something of a double edged sword.