I have a few GM iron blocks in my garage 01,02 4.8l,01 6.0,98 vortec 350.They all measure
out to .125 cylinder wall thickness.This dont make sense cause you can bore 4.8/5.3 block to Ls1 specs but,can't bore 6.0 or vortec 5.7 no where near that much.Anyone have input as to why?

 

This doesnt answer your question entirely but it seems to be a hit or miss if you can bore a 4.8/5.3 to ls1 specs, sometimes the walls arent the same thickness all around so you may have thin spots, but Ive been wondering this myself...

 

I have heard you need to sonic check the 4.8/5.3 block before boring to ls1 spec.

 

Its definently recommended, with a 6.0 you can get it bored .030 over and stroke it to make a 408 and Im pretty sure you can make a 418? from a 6.0 aswell but Im not sure if thats boring more then .030 over or just going with an even bigger stroke. But Im guessing it comes down to the same problem with the 4.8/5.3

 

I know with sonic checking you can get the 6L to 422 ci. I also know you can sonic check a 5.3L and hit 383ci.

I've never heard what that does to reliability, and I haven't seen many people run them for long.

 

Diffrence in bores for Ls1 & 4.8/5.3 is .118.Now bore a 6.0 out to 4.118 w/4" crank you get 427.I want to know why not?

 

GM lists the max overbore for a 6.0L iron block as 0.060", but as with anything, the wall thickness needs to be checked first. Word is there was also some core shift issues with the 6.0's, but by the same token I have never actually heard of anyone having any serious issues with them.

 

Where is that list?Thanks for the input.

 

Well, it looks as if it is not published anymore. I have just about every year catalog and of course they are known for misprints, so I would take what is written with a grain of salt. I also noticed that in every year catalog I went through except 2007, the max stroke is listed as 4.00" for the standard blocks. Where in the 2007 catalog, the max stroke was listed as 4.125" for all the standard blocks.

Of course there is also some information that list's the max overbore as being 0.010" for even the iron block, which we all know is bogus and is for the aluminum motors, except for the earlier models that were 0.005".

 

The only reason I can think of would be a desire to avoid the ragged edge.