Just starting to plan my next engine build for my rcsb and was wondering what the max safe bore size is for a 4.8/5.3 is? This engine is going to be N/A with good heads and a big cam.

 

Many go all the way out to the LS1 bore (3.903' or 3.905" is what most of the aftermarket pistons are) without any issues!

 

@ the title: that's what she said...

i agree with matt. you can safely go out to the LS1 bore, but get it tested before you do it.

 

turn it into a 383.

 

that would be fun

 

Ls1 bore it is. I have been thinking about the 383 but haven't made up my mind yet.

 

I thought the same thing and that was my plan for the 5.3, but the 2 machine shops I deal with would'nt do it! They said they would only bore it if I paid for sonic testing first- and thats about $300.
The best information I could find was by an engine builder on LStech forum- he said "some castings are good, some are not good, I have two 5.3L blocks with holes or paper thin bore walls here in my shop to prove it."

So- in the end I found an LQ4 for $800.

 

While it's true some are good and some are not as good....more are good than bad!

 

The sonic testing may be expensive, but it's cheaper than building an engine twice...or two different engines actually.