Who has their Block Sleeved?
04-01-2002, 08:03 PM
#16
Done With Sidepatch
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What a minute John...Are you saying you are developing an aftermarket oversize piston, with the same expansion characteristics, etc as the OE ( Mahle, Koberschmidt sp? )version that will work in the stock block with no sleeves...You have tweaked my attention and, I'm sure, many others...I may be interested depending on pricing...Keep us posted! <img src="graemlins/bigok.gif" border="0" alt="[thumbsup]" />
04-01-2002, 10:02 PM
#17
Three Wheelin'
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Not sure how well it would apply to this application, but I used to send my Honda cr125 cylinders to US Chrome to get the nikasil redone when I stuck a piston and tore up the bore. Their website is <a href="http://www.usnicom.com." target="_blank">www.usnicom.com.</a> The nikasil (nickel silicon carbide) is much harder and more durable than chrome. This is what comes on a new Honda CR125 motor from the factory, as well as many other motors. I imagine that the nikasil of today is superior to the treatment on the Porsche block from the factory.
04-02-2002, 12:17 AM
#18
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Thread Starter
Yes, Steve, the NiCom coating of which you speak is very, veru interesting. It seems to be a very good alternative (read: cheaper) to having the Porsche block rehoned to original specs. The issue is that I have foudn no imperical data that suggests this is a long-term solution. What I HAVE found is that Jaguar uses the process on thier production engines. This is a good sign. I am specifically interested in increasing the bore size and introducing BOOST on my application, so my choices and research have recently veered towards Block Sleeving.
I must say that this SFR piston development is VERY interesting, and begs for a more indepth look.
John - please excuse my ignorance, but when you say "deck" the block, do you mean a simple "evening out" of the surface, or an actual PLATE that some people weld on the top of the block?
BTW - would You possibly know what compression one would get with a 104mm bore, a 95.25 MM stroke, and a head very similar to a 968 head?
IS thsi too general? I am trying to figure out if I can just buy 5.7inch chevy rods, and get JE to make whatever piston I need to get an 8.5CR....
I must say that this SFR piston development is VERY interesting, and begs for a more indepth look.
John - please excuse my ignorance, but when you say "deck" the block, do you mean a simple "evening out" of the surface, or an actual PLATE that some people weld on the top of the block?
BTW - would You possibly know what compression one would get with a 104mm bore, a 95.25 MM stroke, and a head very similar to a 968 head?
IS thsi too general? I am trying to figure out if I can just buy 5.7inch chevy rods, and get JE to make whatever piston I need to get an 8.5CR....
04-02-2002, 02:19 AM
#19
Burning Brakes
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Hi Brendan,
Yes, by decking the block.../we make sure its flat...there is no cylinder girdle or any hardware added.
As far as the compression goes...we would really need to CC your head, then add the rest into the mix.
OUr pistons are still on the drawing board, but looks good so far. We will run a prototype very soon, within a couple weeks probably. I'm pretty stoked on the options the SFR piston will add to the tuner. I will definately keep you up to date on this.
Yes, by decking the block.../we make sure its flat...there is no cylinder girdle or any hardware added.
As far as the compression goes...we would really need to CC your head, then add the rest into the mix.
OUr pistons are still on the drawing board, but looks good so far. We will run a prototype very soon, within a couple weeks probably. I'm pretty stoked on the options the SFR piston will add to the tuner. I will definately keep you up to date on this.
04-02-2002, 01:25 PM
#20
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Thanks for the info John.
One guy who did a Porsche block added a sort of cement to the bottom of the water-galleys beside the bores, and it was supposed to strengthen the bore tower. he also added a plate to the whole block at the top of the bores
One guy who did a Porsche block added a sort of cement to the bottom of the water-galleys beside the bores, and it was supposed to strengthen the bore tower. he also added a plate to the whole block at the top of the bores
04-05-2002, 07:14 AM
#21
Instructor
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Hello all, first time poster here.
Right Brendan. The guy at the site <a href="http://www.928sg.com" target="_blank">www.928sg.com</a> (seems to be down now), welded 6061 plates to create a "proper" deck for the block. He also filled the block with either machine grout or block filler to stiffen the block (left the top few inches unfilled of course). He then bored (or will bore) the cylinders out and to have them fitted with sleeves.
He was not clear as to whether he had/will completely bored out the cylinders, which would require wet sleeves.
I found his attempt really interesting and I plan on doing something similar but I am doing my own research to make sure it's the way to go.
Regards,
Abdul
Right Brendan. The guy at the site <a href="http://www.928sg.com" target="_blank">www.928sg.com</a> (seems to be down now), welded 6061 plates to create a "proper" deck for the block. He also filled the block with either machine grout or block filler to stiffen the block (left the top few inches unfilled of course). He then bored (or will bore) the cylinders out and to have them fitted with sleeves.
He was not clear as to whether he had/will completely bored out the cylinders, which would require wet sleeves.
I found his attempt really interesting and I plan on doing something similar but I am doing my own research to make sure it's the way to go.
Regards,
Abdul
04-05-2002, 07:24 AM
#22
Drifting
I've heard of this stuff used in bigHP Honda drag engines - but I've always wondered about the expansion difference between the block and grout, and what would seem like the inevitible cracking, etc. after lots of heat cycles...
A bunch of dust and chips in there can't be good, right?
And the deck plate - wouldn't that metal need to be CLOSELY matched to the alloy of the block as well?
Interesting stuff, but doesn't sound like 250K mile tactics...
Anyone else? John? Danno?
A bunch of dust and chips in there can't be good, right?
And the deck plate - wouldn't that metal need to be CLOSELY matched to the alloy of the block as well?
Interesting stuff, but doesn't sound like 250K mile tactics...
Anyone else? John? Danno?
04-05-2002, 09:13 AM
#23
Race Director
Luckily I saved a few photos from that website before it went offline. Ok, I'll expand on the idea of grouting the block and adding a block-brace.
The 928 and 944 engine blocks are very similar with fully wet cylinders (completely surrounded by water). However, this makes the cylinders form individual towers with very little triangulation. Thus all lateral forces have to be taken as a cantilever load on the cylinder walls. Imagine a 2 nd-story patio deck that sticks straight out of the wall. It would have to be extremely thick and heavy to support your weight. Now imagine just adding a little triangulated arm from the outer edge of deck back and down towards the wall. You've just increased the stiffness of the deck by 10 times! The other way of increasing the stiffness of that deck is to reduce it's length and reach from the wall.
That's the idea behind filling the water jackets around the cylinders with grout:
It reduces the exposed length of the cylinders, thus reducing the lateral flexing given the same forces. However, this adds support at the bottom of the cylinders where flexing is lowest.
To really reduce movement of the cylinders at the top (where it flexes the most), you need to reinforce it there. The 928sg used a custom hand-made block-brace that fits into the coolant passages between the cylinders and the outside cylinder block:
As you can see, it's an extremely high-clearance rough fit which is then welded in place. A final machining operation makes the deck completely flush. These upgrades yields the strongest and stiffest cylinders possible for high-compression and high turbo boost. Cars with more mass-market appeal to aftermarket upgraders, like Honda, enjoy a readily available supply of parts like this. You can buy a block-brace for a Honda that's a work of art. Perfectly CNC milled to such exact tolerances, that you simply position the brace into the coolant passages and tap/lightly-pound it into position with a mallet. The precision fit and tightness eliminates any need for welding.
I suspect that cylinder flex is responsible for a large portion of the blown headgaskets on 951s out there. Under high combustion pressures when the engine knocks, I'm sure the fretting between the head, gasket and cylinder tops creates miniscule gaps to develop that allows the intense heat in the chamber to sneak past and burn the headgasket. As can be seen in the later 3.0l engines, Porsche made these modifications themselves. The cylinders are shorter and are also siamesed together for addtional strength. This obviously makes a differnce as can be seen from the numerous 3.0l Turbo cars running around using 18psi of boost and 9.0:1 compression with fewer headgasket problems than a stock 951.
The 928 and 944 engine blocks are very similar with fully wet cylinders (completely surrounded by water). However, this makes the cylinders form individual towers with very little triangulation. Thus all lateral forces have to be taken as a cantilever load on the cylinder walls. Imagine a 2 nd-story patio deck that sticks straight out of the wall. It would have to be extremely thick and heavy to support your weight. Now imagine just adding a little triangulated arm from the outer edge of deck back and down towards the wall. You've just increased the stiffness of the deck by 10 times! The other way of increasing the stiffness of that deck is to reduce it's length and reach from the wall.
That's the idea behind filling the water jackets around the cylinders with grout:
It reduces the exposed length of the cylinders, thus reducing the lateral flexing given the same forces. However, this adds support at the bottom of the cylinders where flexing is lowest.
To really reduce movement of the cylinders at the top (where it flexes the most), you need to reinforce it there. The 928sg used a custom hand-made block-brace that fits into the coolant passages between the cylinders and the outside cylinder block:
As you can see, it's an extremely high-clearance rough fit which is then welded in place. A final machining operation makes the deck completely flush. These upgrades yields the strongest and stiffest cylinders possible for high-compression and high turbo boost. Cars with more mass-market appeal to aftermarket upgraders, like Honda, enjoy a readily available supply of parts like this. You can buy a block-brace for a Honda that's a work of art. Perfectly CNC milled to such exact tolerances, that you simply position the brace into the coolant passages and tap/lightly-pound it into position with a mallet. The precision fit and tightness eliminates any need for welding.
I suspect that cylinder flex is responsible for a large portion of the blown headgaskets on 951s out there. Under high combustion pressures when the engine knocks, I'm sure the fretting between the head, gasket and cylinder tops creates miniscule gaps to develop that allows the intense heat in the chamber to sneak past and burn the headgasket. As can be seen in the later 3.0l engines, Porsche made these modifications themselves. The cylinders are shorter and are also siamesed together for addtional strength. This obviously makes a differnce as can be seen from the numerous 3.0l Turbo cars running around using 18psi of boost and 9.0:1 compression with fewer headgasket problems than a stock 951.
04-05-2002, 09:22 AM
#24
Drifting
ok, so maybe I'm a dunce, but isn't there still a thermal prob with the grout?
Also, how does the coolant circulate if you've welded a lid on the coolant passages?
Also, how does the coolant circulate if you've welded a lid on the coolant passages?
04-05-2002, 09:48 AM
#25
Race Director
Yeah, I was wondering about the coolant passages to the head as well:
I thought he might have drilled holes in the block-brace to line up with the water-passages in the head like with the Honda brace. But looking at the final assembly later, I guess not:
As for the grout, it shouldn't be too much of a problem since the majority of heat in the cylinders occur at the very top. As the piston descends, the gas cools as its energy is converted into mechanical movement.
I thought he might have drilled holes in the block-brace to line up with the water-passages in the head like with the Honda brace. But looking at the final assembly later, I guess not:
As for the grout, it shouldn't be too much of a problem since the majority of heat in the cylinders occur at the very top. As the piston descends, the gas cools as its energy is converted into mechanical movement.
04-05-2002, 04:57 PM
#27
Rennlist Member
It's my understanding that the bulk of the cooling affect is done in the head. So if you fill the bock with grout the thermal load diff. might not be too great.
I'm sure that I'd want to try that on a car stuck in traffic on a day to day basis but it seems it would work on the track.
A friends 426 hemi is filled with grout. He does drive it on the street on occaasion and has no problems.
I'm sure that I'd want to try that on a car stuck in traffic on a day to day basis but it seems it would work on the track.
A friends 426 hemi is filled with grout. He does drive it on the street on occaasion and has no problems.
04-05-2002, 06:22 PM
#28
Neat. I guess that is kind of like most of the factory "air cooled" Porsche race cars from the late 70's through to the early/mid 90's that had water cooled head on the usual air cooled cylinders.
04-05-2002, 09:06 PM
#29
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I presume the grouts expansion rate is different then aluminums or irons. However, it seems that in either case it's not a probelm as block filling is a tried and true methond of block stiffening. I don't know if there is really a difference between machine grout and block filler but I think I would go with the filler since it is marketed for use in engine blocks, better safe than sorry.
Abdul
Abdul
04-05-2002, 09:31 PM
#30
Race Director
The Alusil material used in our blocks is a high-silicon low-expansion aluminum alloy. So you wouldn't have to worry about it expanding so much that the grout breaks loose.
This low-expansion is also a problem with getting aftermarket aluminum pistons. Cold clearances have to be set on the high side because the piston expands more than the block. This leads to a lot of rattling pistons when the engine's cold. You would need a hypereutectic alloy in the pistons along with an iron coating, and I believe SFR is working with JE on some custom pistons just for our cars...
This low-expansion is also a problem with getting aftermarket aluminum pistons. Cold clearances have to be set on the high side because the piston expands more than the block. This leads to a lot of rattling pistons when the engine's cold. You would need a hypereutectic alloy in the pistons along with an iron coating, and I believe SFR is working with JE on some custom pistons just for our cars...