This is just my luck. I purchased a used 5.3 motor and was gonna bore it to 3.903 so I could reuse my current rotating assembly. Machine shop called and said they didn't feel comfortable going up to 3.903. I don't have the sheet handy, but he seemed to indicate there was alot of core shift in the block. I will run up there tomorrow after work, but just wanted numbers so I knew what the norm was.

 

Every block is different. There is a minimum thickness they like to maintain. I am not 100% positive but I believe on a naturally aspirated setup they like to maintain a .200 minumum wall thickness.

You should ask them while there down there.

 

it will be fine. i currently just had my 5.3 bored to 3.903. i did however have to call several shops before i found one that had a clue about doing LS blocks. you will be taking out .125" out of each cylinder.

 

Not if he has core shift like he mentioned. Some guys have gone through the cylinder walls trying to get stock LS1 3.898 bore. If your shop says no after a sonic check, there may be a reason.

 

i did a bit of research on core shift and it seems to be a bigger problem with LT blocks. i havent found any info on core shift being an issue on the newer LS blocks but i have been wrong before.

 

I've seen it a couple of times(core shift).

 

Well, went to the shop to talk to the machinist about it, and here is the skinny. He at the absolute least wants to keep the cylinders on a small block motor around the .120" range if it's going to be a street/strip motor. No guarantees if you go that thin he said. He likes to keep it thicker on the thrust side of the bore. Putting 3.903 pistons in it would mean taking about .062 from each side of the wall. Some have plenty of meat in there, some not so much.

At this point I'm kinda ticked off for the sake of being ticked off I guess because this screws up my whole plan of reusing alot of my 5.7 parts.

 

Bummer, always sucks when you got parts lined up for a build and you find out they won't be compatible.

Imo part out the 5.3 if you got it cheap enough, to recoup a little bit of your money or sell the LS1 pistons and get yourself a set of Wiseco 5.3 pistons and keep it stock bore. I am considering building my 5.3 over the winter as I can do pistons and rods for $1k and have something that will handle 15psi for when I boost.

 

Yeah, I got it cheap enough. I'd just like to get this thing running though. Anybody have a good set of 4.8 pistons they wouldn't mind letting go for a fair price?

 

Do you just have a regular LS1 assembly or is a forged one?
Get the 05+ 4.8 pistons and a set of LS2 rods if you don't already have good ones... little bit of a beefy budget build