Who has their Block Sleeved?
04-08-2002, 06:58 PM
#31
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Thread Starter
Danno -
I met Sterling Gee, the man of which we speak, and the engine you posted the pictures of. I am confused, as that page is still there, with those pictures?
This was also an engine that recieved the 968 vario cam technology (for a 928 engine, 5.0L), but thats for another thread.
This block-stiffening is a very important subject, and begs more research. A stiffer block is a more durable block, and a more durable block is one that will last for many many more miles on the street and track. This then becomes more of an investment than an experiment.
I was thinking about either a deck-plate or some grout when I stroke and bore my engine. (It will be sleeved).
I met Sterling Gee, the man of which we speak, and the engine you posted the pictures of. I am confused, as that page is still there, with those pictures?
This was also an engine that recieved the 968 vario cam technology (for a 928 engine, 5.0L), but thats for another thread.
This block-stiffening is a very important subject, and begs more research. A stiffer block is a more durable block, and a more durable block is one that will last for many many more miles on the street and track. This then becomes more of an investment than an experiment.
I was thinking about either a deck-plate or some grout when I stroke and bore my engine. (It will be sleeved).
04-08-2002, 09:12 PM
#32
Race Director
" I am confused, as that page is still there, with those pictures?"
I'm confused too. What's the website addresses since the old one's not working?
As for grouting and deck-bracing, I'd do both while you're in there as you don't want to be tearing that engine apart later.
One issue that hasn't been brought up is the more flexible cylinder walls from sleeving. By having the cylinders made up of two layers instead of one, you end up with twice the flex.
It's like having two springs in series on top of each other. The applied load goes from one to the other and compresses each one independently, giving you twice the displacement.
Sure, a steel sleeve is stiffer than the aluminum part of the cylinder you removed, but it's also thinner than the original cylinder. And the original cylinder is now a thinner alloy one as well. So a 2mm+4mm cylinder certainly is not as strong and stiff as the original solid 8mm one.
I'd do both the grouting and deck-bracing to be on the safe side.
I'm confused too. What's the website addresses since the old one's not working?
As for grouting and deck-bracing, I'd do both while you're in there as you don't want to be tearing that engine apart later.
One issue that hasn't been brought up is the more flexible cylinder walls from sleeving. By having the cylinders made up of two layers instead of one, you end up with twice the flex.
It's like having two springs in series on top of each other. The applied load goes from one to the other and compresses each one independently, giving you twice the displacement.
Sure, a steel sleeve is stiffer than the aluminum part of the cylinder you removed, but it's also thinner than the original cylinder. And the original cylinder is now a thinner alloy one as well. So a 2mm+4mm cylinder certainly is not as strong and stiff as the original solid 8mm one.
I'd do both the grouting and deck-bracing to be on the safe side.
04-14-2002, 06:04 AM
#33
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Hi folks,
FYI the SG site is back up, <a href="http://www.928sg.com." target="_blank">www.928sg.com.</a>
As for sleeve flexing I doubt it is an issue. For one thing it's possible that it will act like a laminate which would actually make it stronger than a single unit... that is just an unformulated thought, the dynamics behind it are complex and would need an engineer to flesh it out. The other thing is that sleeves are extreemly stiff. Sleeves and liners are generally spin-cast and made up of alloyed iron, ductile iron, or alloyed steel. The metals are specifically designed to have an extremely stiff structure. The tensile strength and flexural strength of a sleeve are anywhere from 2 to 7 times that of hyper-eutectic aluminum depending on the material.
I think the cylinder configuration is plenty stiff, but it would be useful to know what kind of sleeves the gentleman used. I am working on a similar project, however I am looking into liners instead, but it all depends on how much bore I decide to go with.
Regards,
Abdul
FYI the SG site is back up, <a href="http://www.928sg.com." target="_blank">www.928sg.com.</a>
As for sleeve flexing I doubt it is an issue. For one thing it's possible that it will act like a laminate which would actually make it stronger than a single unit... that is just an unformulated thought, the dynamics behind it are complex and would need an engineer to flesh it out. The other thing is that sleeves are extreemly stiff. Sleeves and liners are generally spin-cast and made up of alloyed iron, ductile iron, or alloyed steel. The metals are specifically designed to have an extremely stiff structure. The tensile strength and flexural strength of a sleeve are anywhere from 2 to 7 times that of hyper-eutectic aluminum depending on the material.
I think the cylinder configuration is plenty stiff, but it would be useful to know what kind of sleeves the gentleman used. I am working on a similar project, however I am looking into liners instead, but it all depends on how much bore I decide to go with.
Regards,
Abdul
04-14-2002, 06:37 AM
#34
Race Director
"For one thing it's possible that it will act like a laminate which would actually make it stronger than a single unit..."
Well, it's not the strength that I was talking about, but rather the rigidity (stiffness) given any amount of load. Strength & ridigity are two completely different factors. One is how much force a given sample can take before it takes a permananet set or breaks, while the other is the amount of deflection for that force.
For example, plywood is 'stronger' than solid panels, because it can hold more weight before it breaks. But at a lesser amount of weight, it bends and flexes much more than a solid piece of wood.
Also Titanium vs. Steel. For any given same-sized sample, a piece of 6al/4va Ti will flex twice as much under the same load as the steel. Yet the Ti will take about twice the load as the steel piece before it takes a permanent set or breaks.
Same thing with the cylinders. We're not so much concerned about the combustion pressure blowing them open, just how much fretting occurs at the top against the headgasket. As you can see from the evolution of the 2.5L block to the 3.0L block, the cylinders have been reinforced significantly, so this was obviously a concern for Porsche.
Also the ridigity of a sample is given from it base alloy and its 3D geometry. While steel is 3x stiffer than aluminum, the sleeves are also 3x (or more) thinner than the overall thickness of the original cylinders. Additionally, the rigidity of a tube is a function to the 4th power of the diameter. So again, the thicker, larger diameter of the original cylinder is still stiffer than the sleeve.
Unless you can make a 2mm sleeve out of something super-stiff like Boron or Beryllium, the overall process of sleeving will yield a more flexible cylinder.
One way around this is to somehow weld the sleeve to the original cylinders (along their entire mating surfaces) so that you don't have the spring-on-top-of-a-spring issue of double deflection. In which case, it would act as a single layer rather than a flexible laminate.
Well, it's not the strength that I was talking about, but rather the rigidity (stiffness) given any amount of load. Strength & ridigity are two completely different factors. One is how much force a given sample can take before it takes a permananet set or breaks, while the other is the amount of deflection for that force.
For example, plywood is 'stronger' than solid panels, because it can hold more weight before it breaks. But at a lesser amount of weight, it bends and flexes much more than a solid piece of wood.
Also Titanium vs. Steel. For any given same-sized sample, a piece of 6al/4va Ti will flex twice as much under the same load as the steel. Yet the Ti will take about twice the load as the steel piece before it takes a permanent set or breaks.
Same thing with the cylinders. We're not so much concerned about the combustion pressure blowing them open, just how much fretting occurs at the top against the headgasket. As you can see from the evolution of the 2.5L block to the 3.0L block, the cylinders have been reinforced significantly, so this was obviously a concern for Porsche.
Also the ridigity of a sample is given from it base alloy and its 3D geometry. While steel is 3x stiffer than aluminum, the sleeves are also 3x (or more) thinner than the overall thickness of the original cylinders. Additionally, the rigidity of a tube is a function to the 4th power of the diameter. So again, the thicker, larger diameter of the original cylinder is still stiffer than the sleeve.
Unless you can make a 2mm sleeve out of something super-stiff like Boron or Beryllium, the overall process of sleeving will yield a more flexible cylinder.
One way around this is to somehow weld the sleeve to the original cylinders (along their entire mating surfaces) so that you don't have the spring-on-top-of-a-spring issue of double deflection. In which case, it would act as a single layer rather than a flexible laminate.
04-15-2002, 12:52 AM
#35
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Right, right. I mispoke and meant rigidity in regards to my comment on laminate. In anycase, I agree with about sleeving being a less than ideal compromise; but I am still not too worried about it in the real world... as long as it was installed correctly.
In regards to getting the sleeve to bond with the block, I suppose you could impregnate the outside surface of the sleeve with a compound that would cause it to bond to the block (through electolosys perhaps). Of course, that is complex and I don't know if the bond would be strong enough to maintain itself in extreme enviroments.
A different solution would have been to use a liner instead, which has a much thicker wall vs. a sleeve. Of course, the liner requires a larger bore to slip into and may not allow for as large a bore. I am looking into a liner solution right now, but I have not decided on my bore size yet, so I don't know how that will pan out.
Regards,
Abdul
In regards to getting the sleeve to bond with the block, I suppose you could impregnate the outside surface of the sleeve with a compound that would cause it to bond to the block (through electolosys perhaps). Of course, that is complex and I don't know if the bond would be strong enough to maintain itself in extreme enviroments.
A different solution would have been to use a liner instead, which has a much thicker wall vs. a sleeve. Of course, the liner requires a larger bore to slip into and may not allow for as large a bore. I am looking into a liner solution right now, but I have not decided on my bore size yet, so I don't know how that will pan out.
Regards,
Abdul
04-15-2002, 01:15 PM
#36
Rennlist Member
Thread Starter
I see that this thread has crept up again. I started it, so I may as well continue:
Chromemoly is the material that some use, and others use alloy, but I am unsure on the make-up.
What is the difference between the sleeve that I was originally talking about, and a "liner" as you have now brought up?
I think the reinforcement is a very important sub-topic in the sleeving area, as if you are leeving, you are talking about some serious changes to the engine. Is it true that the 968 block is simesed?
The "plating" is a concern for me, as it looks so "dirty" to do, and it really is tricky to weld these blocks, and not have them change thier shape, correct?
I have decided on sleeving, but I want to make sure I do more than enough research on the surrounding parameters (reinforcement, grouting, etc) before my engine goes under the knife. Everything else is straightforward - rods, pistons, crank(ordered), heads. The sleeving area has alot of here-to-there play....
Chromemoly is the material that some use, and others use alloy, but I am unsure on the make-up.
What is the difference between the sleeve that I was originally talking about, and a "liner" as you have now brought up?
I think the reinforcement is a very important sub-topic in the sleeving area, as if you are leeving, you are talking about some serious changes to the engine. Is it true that the 968 block is simesed?
The "plating" is a concern for me, as it looks so "dirty" to do, and it really is tricky to weld these blocks, and not have them change thier shape, correct?
I have decided on sleeving, but I want to make sure I do more than enough research on the surrounding parameters (reinforcement, grouting, etc) before my engine goes under the knife. Everything else is straightforward - rods, pistons, crank(ordered), heads. The sleeving area has alot of here-to-there play....
04-15-2002, 09:11 PM
#37
Race Director
Here's a photo comparing a 2.5ltr 951 block to the later 3.0ltr ones:
As you can see, the cylinders are siamesed for bracing and the external ribs on the block are beefier as well. Now considering that the 3.0ltr engines can't possibly stress their cylinders as much as a modified 951 under 15-20psi of boost, there was enough of a concern somewhere within Porsche to add these reinforcements.
Anyway Brendan, if you do the welded-in block-brace like on the 928sg car, you should have an even stronger block. The alloy in our block is a hypereutectic 390-alloy (Alusil) with roughly a 30% silicon mix. Since aluminium can only take up to 12% silicon in solution, the excess silicon percipitates out as crystals. So we're really looking at an MMC (metal-matrix composite) block rather than an aluminium alloy.
Just make sure the guy welding the block knows these details. Also some post-welding annealing of the entire block in an oven would help relieve stresses. Then the final boring and deck-machining should give you the strongest block possible!
As you can see, the cylinders are siamesed for bracing and the external ribs on the block are beefier as well. Now considering that the 3.0ltr engines can't possibly stress their cylinders as much as a modified 951 under 15-20psi of boost, there was enough of a concern somewhere within Porsche to add these reinforcements.
Anyway Brendan, if you do the welded-in block-brace like on the 928sg car, you should have an even stronger block. The alloy in our block is a hypereutectic 390-alloy (Alusil) with roughly a 30% silicon mix. Since aluminium can only take up to 12% silicon in solution, the excess silicon percipitates out as crystals. So we're really looking at an MMC (metal-matrix composite) block rather than an aluminium alloy.
Just make sure the guy welding the block knows these details. Also some post-welding annealing of the entire block in an oven would help relieve stresses. Then the final boring and deck-machining should give you the strongest block possible!
04-16-2002, 06:47 AM
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Hello Brendan,
Danno nailed the point about block warpage, have as much machine work done after the block has been welded. There should not be much warpage as the block should maintain it's structure, but do stress relieve if you can, and definitely squareing the block after the weld is the way to go.
As for liners vs. sleeves...
Sleeves are pressed into the bore and use the surrouding material to hold them in place, and for structural reinforcement.
Liners slip fit into the block, they are supported at the deck and the base. The wall thickness of a liner is about twice as thick as a sleeve, it's integrity does not depend on any surrouding material. Liners can be wet, where they make up the entire cylinder component and coolant comes into contact with the liner. Dry liners slip into an existing bore, where the cooling passages are sealed off (like a sleeve in a regular cylinder bore). Liners generally have flanges at the top (a liner from the side has a T shape) which sit in precisely matched pockets in the deck. I have seen pictures of liners simply held down by the clamping force of the cylinder head and others that are retained by bolts.
The downside of liners (that I am concerned about) is that they require room to accomodate their flanges and that they require reliefs to be machined into the deck. Wet liners can leak coolant out the bottom, if the liner base does not seal properly.
A lot of dragster engines use cylinder liners, I am talking Top Fuel mills. Liners are also popular with industrial equipment, i.e.: Caterpiller, GM, and John Deer engines.
I hope that all makes sense, I would post some pix but I am a bit wiped right now. I'll put some up tomorrow.
Regards,
Abdul
Danno nailed the point about block warpage, have as much machine work done after the block has been welded. There should not be much warpage as the block should maintain it's structure, but do stress relieve if you can, and definitely squareing the block after the weld is the way to go.
As for liners vs. sleeves...
Sleeves are pressed into the bore and use the surrouding material to hold them in place, and for structural reinforcement.
Liners slip fit into the block, they are supported at the deck and the base. The wall thickness of a liner is about twice as thick as a sleeve, it's integrity does not depend on any surrouding material. Liners can be wet, where they make up the entire cylinder component and coolant comes into contact with the liner. Dry liners slip into an existing bore, where the cooling passages are sealed off (like a sleeve in a regular cylinder bore). Liners generally have flanges at the top (a liner from the side has a T shape) which sit in precisely matched pockets in the deck. I have seen pictures of liners simply held down by the clamping force of the cylinder head and others that are retained by bolts.
The downside of liners (that I am concerned about) is that they require room to accomodate their flanges and that they require reliefs to be machined into the deck. Wet liners can leak coolant out the bottom, if the liner base does not seal properly.
A lot of dragster engines use cylinder liners, I am talking Top Fuel mills. Liners are also popular with industrial equipment, i.e.: Caterpiller, GM, and John Deer engines.
I hope that all makes sense, I would post some pix but I am a bit wiped right now. I'll put some up tomorrow.
Regards,
Abdul
04-19-2002, 04:19 AM
#39
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why not post some pictures of the liners/sleeves?
Danno - can you go over the physics behind your flex theories? (some simple analogies might help)
Thanks <img src="graemlins/jumper.gif" border="0" alt="[jumper]" />
Danno - can you go over the physics behind your flex theories? (some simple analogies might help)
Thanks <img src="graemlins/jumper.gif" border="0" alt="[jumper]" />
04-19-2002, 05:34 AM
#40
Race Director
Basic spring-rate equations will explain this. Two layers of any material on top of another (in series) will have roughly double the deflection given the same load. Like the plywood vs. solid wood of the same thickness in the example above.
Another is the double-spring example. Take a 12" spring of say... 200lb/in. With a load of 200lbs, it will compress 1", fine. Now take 2 6" springs of the same rate 200lb/in and stack them on top of each other and apply the same 200lb load, what do you get?
The 200lb load compresses the 1st spring 1". That spring then applies the SAME load unaffected to the top of the next spring below and compresses THAT another 1" for a total compression of 2".
You can also use the springs-in-series equations to figure that out as well. Given two springs X and Y with rates of Xr and Xy, you can figure out their combined effective spring-rates (when stacked) Zr as follows:
Let's take a qualitative look at what happens with cylinder-sleeving then. Assuming we have a 6mm cylinder that flexes... say... 1mm under normal use (exaggerated for this example). Then we bore it out to accept a sleeve/liner of larger-than-stock inner-diameter. So we take 3mm out of the inner diameter of the cylinders. Now our flex is up to 1.5mm.
The sleeve would be an even thinner, smaller-diameter tube than the cylinders, so it would have even more flex. But since it's made from a stiffer material, it may have around the same flex for a given force as the larger-diamter thicker cylinders. So a 2mm thick sleeve might have 2mm of deflection. Individually, the bored-out cylinder and the sleeve has more flex than the original thicker cylinder (this part is important).
When you stuff this 2mm sleeve into the bored-out 3mm-thick cylinder, the total flex will still be based the minimum amount either one moves by itself. In this case, the 1.5mm flex of the cylinder.
It would occur in this order. The gas goes BOOM in the cylinder and pushes on the sleeve. Which then tries to flex 2mm and pushes on the outer cylinder. Since the outer cylinder will only flex 1.5mm by itself, it will then only flex 1.5mm, containing and limiting the sleeve's flex to 1.5mm. So the total flex in this case is 1.5mm or 50% more than the original thick cylinder.
You can actually over bore to the point where the outer cylinder is so thin, that it has more flex than then sleeve. Such as individual deflections of 2.0mm for the sleeve, but 2.5mm for the outer cylinder. In this case, under load, the outer cylinder would be weaker than the sleeve and wouldn't apply any resistance 'clamping' force under pressure to hold the sleeve in place.
Now these are just qualitative examples I used to illustrate this point. I'll have to make a MathCAD model to determine the exact numbers, but you get the idea.
Another is the double-spring example. Take a 12" spring of say... 200lb/in. With a load of 200lbs, it will compress 1", fine. Now take 2 6" springs of the same rate 200lb/in and stack them on top of each other and apply the same 200lb load, what do you get?
The 200lb load compresses the 1st spring 1". That spring then applies the SAME load unaffected to the top of the next spring below and compresses THAT another 1" for a total compression of 2".
You can also use the springs-in-series equations to figure that out as well. Given two springs X and Y with rates of Xr and Xy, you can figure out their combined effective spring-rates (when stacked) Zr as follows:
- 1/Zr = ( 1/200 + 1/200 ) = 1/100
- Zr = 100lb/in
Let's take a qualitative look at what happens with cylinder-sleeving then. Assuming we have a 6mm cylinder that flexes... say... 1mm under normal use (exaggerated for this example). Then we bore it out to accept a sleeve/liner of larger-than-stock inner-diameter. So we take 3mm out of the inner diameter of the cylinders. Now our flex is up to 1.5mm.
The sleeve would be an even thinner, smaller-diameter tube than the cylinders, so it would have even more flex. But since it's made from a stiffer material, it may have around the same flex for a given force as the larger-diamter thicker cylinders. So a 2mm thick sleeve might have 2mm of deflection. Individually, the bored-out cylinder and the sleeve has more flex than the original thicker cylinder (this part is important).
When you stuff this 2mm sleeve into the bored-out 3mm-thick cylinder, the total flex will still be based the minimum amount either one moves by itself. In this case, the 1.5mm flex of the cylinder.
It would occur in this order. The gas goes BOOM in the cylinder and pushes on the sleeve. Which then tries to flex 2mm and pushes on the outer cylinder. Since the outer cylinder will only flex 1.5mm by itself, it will then only flex 1.5mm, containing and limiting the sleeve's flex to 1.5mm. So the total flex in this case is 1.5mm or 50% more than the original thick cylinder.
You can actually over bore to the point where the outer cylinder is so thin, that it has more flex than then sleeve. Such as individual deflections of 2.0mm for the sleeve, but 2.5mm for the outer cylinder. In this case, under load, the outer cylinder would be weaker than the sleeve and wouldn't apply any resistance 'clamping' force under pressure to hold the sleeve in place.
Now these are just qualitative examples I used to illustrate this point. I'll have to make a MathCAD model to determine the exact numbers, but you get the idea.
04-20-2002, 01:15 AM
#42
Race Director
Nope, you'll always have more flex than the stock cylinders due to having two thin layers that are more flexible than the single thick stock one.
Just that boring out the stock cylinder and putting in a sleeve that's thinner than the amount you bored allows you to use larger pistons. Also gives you a wider selection of pistons since you've got a steel bore now rather than the original Alusil one (which only works with iron-coated pistons).
Just that boring out the stock cylinder and putting in a sleeve that's thinner than the amount you bored allows you to use larger pistons. Also gives you a wider selection of pistons since you've got a steel bore now rather than the original Alusil one (which only works with iron-coated pistons).
07-02-2002, 05:51 PM
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John Anderson,
Anything happening with the pistons you were developing? I read over this thread with great interest, since i'm about to have to buy something and i'm not too keen on dumping 3/4 of my rebuild budget on pistons alone! Hope the plans didnt get skuttled.
I also emailed you about a motor -call me if you can. <img src="graemlins/beerchug.gif" border="0" alt="[cheers]" />
thanks,
kelly
Anything happening with the pistons you were developing? I read over this thread with great interest, since i'm about to have to buy something and i'm not too keen on dumping 3/4 of my rebuild budget on pistons alone! Hope the plans didnt get skuttled.
I also emailed you about a motor -call me if you can. <img src="graemlins/beerchug.gif" border="0" alt="[cheers]" />
thanks,
kelly
05-03-2005, 11:02 PM
#45
Developer
John Anderson and Danno -
I build supercharger kits for the 928...
www.928motorsports.com
Most of our customers are happy in the 6 - 10 psi range and we have not had a problem with trumpeting the cylinder walls under boost at this level.
I *think* but I do not know, that the 951 may have thicker cylinder walls than the 928 in preparation for boost - but I do not have a 944 turbo block to measure. If someone could and tell me what you find out that'd be nice.
Here is my real question: I saw the 928SG site too... and am looking for solutions to cylinder wall flexing and trumpeting as we turn the boost up.
I have a sleeved 928 block that I bought already sleeved and I gotta tell ya, by the time the bore was cut to accept the steel sleeve, there isn't a lot of aluminum left around the steel to support it...
My concern is that the steel will expand farther than the surrounding Reynolds 396 alloy and crack my relatively thin aluminum cylinder walls. For you other readers: our engine's alloy is not typical among aluminum engines for another reason beyond the MMC inclusion of silicone. The alloy our blocks are machined from also has an expansion ratio of zero.
In fact, when I look at the 928SG engine, his cradle may be made from 6061 or other hi-expansion alloy and he has just welded that into this Reynolds 396 block... he could be in a lot of trouble! Time will tell.
Anyway - back to my idea:
Here is what I am thinking about doing - tell me what you think. I am going to make a temporary solid gasket with no water or cylinder holes in it from plastic sheet, and clamp it between the block and the head. Torque the head down normally to stress the block in the normal directions.
Turn the block over on a engine stand so that 4 cylinders are straight down.
Pour in about 1 inch of block filler, lay in a reinforcing fiberglass mesh, then pore in another inch on top of that.
After it hardens, use a normal engine gasket as a template and drill my water passageways into what is now a solid top-cylinder cradle. The reinforcing mesh laid in during the pour is there to prevent the cement from cracking during and after it is drilled.
I have been calling manufacturers of block filler to locate the right product... one issue is strength, another is if the hardening product should discplace the cylinder walls into another axis, then the block has to be bored again. The third issue is the tolerance to temperature: the outer cylinder walls down low are commonly at or just above water temp - about 250 deg F. But at the top of the cylinders, the cylinder wall temp on the water jacket side is believed to be about 550 deg F by most.
I looked at Moroso's block filler product - it is grout-based and can take the heat. But it will move the cylinders as it hardens and the engine must be re-bored after use. The Moroso technicians I spoke to said that their product would not be good in this application.
I went to TN and looked at BLOCKPOXY. Nice product, and being epoxy-based, it pours like Karo syrup and easily can get between cylinder pairs and small passageways. But it is not good above about 350 deg F.
The winner so far seems to be HARD BLOK brand. It is cement-based, can handle temperatures up to 1200 deg F, has 8,000 psi compression strength, and does not change the cylinder alignment as it cures at all. Their product has pulverized iron in it so it drills ike steel. They say they have used it in aluminum engines with success several times, including one nut that filled the top of his engine with it (not the bottom) like me.
What do YOU think of this plan?
I build supercharger kits for the 928...
www.928motorsports.com
Most of our customers are happy in the 6 - 10 psi range and we have not had a problem with trumpeting the cylinder walls under boost at this level.
I *think* but I do not know, that the 951 may have thicker cylinder walls than the 928 in preparation for boost - but I do not have a 944 turbo block to measure. If someone could and tell me what you find out that'd be nice.
Here is my real question: I saw the 928SG site too... and am looking for solutions to cylinder wall flexing and trumpeting as we turn the boost up.
I have a sleeved 928 block that I bought already sleeved and I gotta tell ya, by the time the bore was cut to accept the steel sleeve, there isn't a lot of aluminum left around the steel to support it...
My concern is that the steel will expand farther than the surrounding Reynolds 396 alloy and crack my relatively thin aluminum cylinder walls. For you other readers: our engine's alloy is not typical among aluminum engines for another reason beyond the MMC inclusion of silicone. The alloy our blocks are machined from also has an expansion ratio of zero.
In fact, when I look at the 928SG engine, his cradle may be made from 6061 or other hi-expansion alloy and he has just welded that into this Reynolds 396 block... he could be in a lot of trouble! Time will tell.
Anyway - back to my idea:
Here is what I am thinking about doing - tell me what you think. I am going to make a temporary solid gasket with no water or cylinder holes in it from plastic sheet, and clamp it between the block and the head. Torque the head down normally to stress the block in the normal directions.
Turn the block over on a engine stand so that 4 cylinders are straight down.
Pour in about 1 inch of block filler, lay in a reinforcing fiberglass mesh, then pore in another inch on top of that.
After it hardens, use a normal engine gasket as a template and drill my water passageways into what is now a solid top-cylinder cradle. The reinforcing mesh laid in during the pour is there to prevent the cement from cracking during and after it is drilled.
I have been calling manufacturers of block filler to locate the right product... one issue is strength, another is if the hardening product should discplace the cylinder walls into another axis, then the block has to be bored again. The third issue is the tolerance to temperature: the outer cylinder walls down low are commonly at or just above water temp - about 250 deg F. But at the top of the cylinders, the cylinder wall temp on the water jacket side is believed to be about 550 deg F by most.
I looked at Moroso's block filler product - it is grout-based and can take the heat. But it will move the cylinders as it hardens and the engine must be re-bored after use. The Moroso technicians I spoke to said that their product would not be good in this application.
I went to TN and looked at BLOCKPOXY. Nice product, and being epoxy-based, it pours like Karo syrup and easily can get between cylinder pairs and small passageways. But it is not good above about 350 deg F.
The winner so far seems to be HARD BLOK brand. It is cement-based, can handle temperatures up to 1200 deg F, has 8,000 psi compression strength, and does not change the cylinder alignment as it cures at all. Their product has pulverized iron in it so it drills ike steel. They say they have used it in aluminum engines with success several times, including one nut that filled the top of his engine with it (not the bottom) like me.
What do YOU think of this plan?