HemiChallenger said:
I've heard the 5.7 aluminum blocks that use an aftermarket kit with bigger bore sleeves move around a lot more and aren't as reliable/wont tolerate as much power as say a C5R block, iron truck block or LS2 block. Any truth to that?
Sleeve dropping isn't really the biggest issue with Darton MID or most wet sleeve conversion blocks. A dry sleeve design block still has main bearing galley strength contributions. the bottoms of the bores help act as truss's between the journals. the reason so many sleeves leak etc is becuase the register surface is alway moving around due to lower end flex. Now a properly designed wet sleeve block IE diesels etc have extra structure added to the block to increase main journal support. Also the inline 6 configuration ( you will notice most V8 diesels aside from detroits Bus engines ( I would have to check on that one ) do not use flaoting wet sleeves )with one main journal per cylinder has alot more stress disspation over a longer longitudnal axis. IE each main carrys 1/6 of the load instead of 1/4 of the load. also looking at most inlnes six designs you will see in diesel application that there is a heavy emphasis on block wall IE outer water jacket main journal stabilizing 6 bolt mains etc. All of this creates a floating cylinder case idealogy that works with the floating or press in wet sleeve design. the factory LS1 blocks do not have the added material with the exception of the C5r block to support a Wet sleeve design cylinder without to many strength comprimises but its still not Ideal.
the raitonalization I often here for the MID sleeve kit is cylinder sealing and wall intergrity. While this is a sound argument the offset loss of lower end main bearing journal stability is so far comprimised that leaking and breakage occour in the applications i have seen run at the upper limits of power production per inch of displcement, My way of saying high RPM turbo and supercharged engines show more failures then High RPM NA motors. This lends itself directly to the statements i just made about removing lower end strength. It would look like a High RPM engine would load the main bearings more but if the engine is 50/50 % rotating recipricating balanced and balanced well the thrust load changes between 5000 and 8000 rpm aren;t that drastic. However rod loading is magnitudes higher. the limiting factor directly is thrust load overall. You stand as good a chance beaking a sleeved engine at 1000ft lb regardless of weather its 4000rpm peak or 6000rpm peak. although the lower rpm tq peak would proboaly break first becuase the main loads will be much higher per cobustion pulse. But understand my point here. I am saying total thrust load is really whats going to break the lower end.
As for cylinder sealing issues. If the aluminum blocks are marginal at 650hp then don't use one. After seeing some high horse boost applications comming apart as of late for forensics I think the jury is in on this. the stock Ls1 and most likely the ls2 block ( cylinder walls are thicker but haven't seen testing so i treat it the same as a Ls1 block until proven otherwise) wont be to capable of reliable long term durability beyond 650hp boosted this will of course depend on rpm as well. limit the Tq to 600ft lbs then you might be able to make it up with rpm therby bypassing some cylinder wall sealing issues not to mention deck rigidity on both the head and the block.
If you want to make big boosted power with the LSx engines and have excelent ring seal and durability then look at the truck block upto 900h ( wall thickness is a bit thin on the thrust side) and beyond that look at the offerings from World Prodcuts or the C5r and or Ls7 blocks. Beyond 1200hp your only good long term reliable case is the world products case. It has alot more main bearing support and is thicker in the cylinder walls outer aluminum and inner iron dry liners. not to mention vast improvements in head sealing surface strength 6 bolts per cylinder and a vastly thicker deck surface.
do not take this as a blanket statement more power has been made with the production blocks then i am recomending but durability issues creep up long term.
with billet main caps and block filler you could stretch the power handling capabilitys some 40-50% but it will suffer massive heating cooling issues for street usage.
and agian I am aware guys are making lots of power with production blocks as of late though on teardowns I have been into the blocks show signs of serious flex and stress in the fact that even things like line bore and concentricity for both the main and the camshaft tunnels seem to be moving around alot requiring machining operations to bring them into even GM's widest allowable tolerances.
then there have been the very barrel shapped bore popping up at the very high output levels 1400-1600hp range even with the iron blocks.
I wish there were better alternatives but you work with what you've got.Agian I know people have made tons of power on stock blocks. these are what i treat as the dialy driver maximum abuse levels for long term 50K service life. Just IMO but please don't flame.
