On my LS1 block the inside of the block is very smooth. No casting at all on the surfaces. On this new LS6 block that I got from Ariel Performance it has casting every where. I expected some high spots but all surfaces are very rough and seems like they will catch oil.

Any ideas why the big difference?

 

I have seen rough looking LS1 blocks too so that may not mean anything. I think the only real difference between the two blocks is the crank case vent holes- LS6 have the better design cast in(also in a higher location) where the LS1 has the machined in that is more prone to crack because of the stress riser and the closeness of the hole to the main journal and oil feed port.

 

The ls1 block is die cast whereas the ls6 block and later are sand cast hence the different appearance. I think the matallurgists here will opine that sand cast blocks are stronger due to the longer cooling down process which allows better integrity.

 

Thanks!

 

I tend to disagree here on that the LS6 is stronger because of the sand cast. To get a "harder" metal, you would want to quench the metal very quickly to preserve the beta Fe phase in the metal and the Mg2Si distribution. However, metal hardness and other properties are mostly dependant on the alloy of the metal.
The only advantage of Die casting vs. sand casting - Die casting produces parts with thinner walls, closer dimensional limits and smoother surfaces. Production is faster and labor costs per casting are lower. Finishing costs are also less.

 

That was my wife, (BTW she's a Metallugist at ALCOA which builds aluminum parts for everything from motor blocks to aircraft parts) If you look the LS6 and LS1 blocks are the same alloy. Any differences in the blocks are in the casting itself. FWIW, I thought, but not certain alot of the the venders on here didn't like to use the LS6 block when constructing aluminum motors that have the sleeves replaced for some reason. Somebody with alittle more knowledge on that has to chime in and give a reason.

 

Interesting point but I'm not sure GM were after a harder metal. I thought they wanted everything to take longer to cool down so the metal became more stable. There was a very good thread about this on this forum a while back and it's worth finding. The earlier blocks don't have the windows at the base of the liners and some people say they are stronger in that area. Without data it's impossible to say which is truly stronger. I'd use whatever block was available but for my own engine I'd go with the ls6 but only just.