5.3 pistons

[Gunnin4ya]

I searched and couldn't find an answer for some reason. My question is will 3.809 piston work when my machinist says the block is 3.810 without problems? My first is build and don't want to screw up. I can find a ton of 3.809 piston but trouble finding 3.810. Thanks in advance.

[88Stanger]

have it bored out .020 over stock and get .020 over pistons

[71cadc10]

some pistons (most) are listed in a size for the finished bore. so a piston labelled 3.809 is the bore size the block should be machined to.
the actual piston measured might be ~.003" under that.

http://https://www.summitracing.com/parts/slp-h1132cpa75mm/overview/make/chevrolet

if you look at the p/n's for something like this...basically the stock replacement GM piston...the end of p/n has 75MM. Since we are talking 5.3L and everything is metric now...that is 0.75mm over size (=.030").
if you see a 50MM at end...it is 0.5mm oversize (=.020").
These oversize numbers is what the bore should finish at in the block, the pistons are smaller when you measure them to give proper clearance.

I guess you need to clarify with your machinist what exactly you need...sounds like he is talking .030 (0.75mm) over stuff.
or better yet maybe ask him to source the pistons if the price is fair...and then he's on the line to get it all married together

[Root2812]

I agree with that 71cadc10 said. When I did my first engine build (a 5.3 also) I had my machinist order the pistons for me and when I picked up my engine I got the new pistons already attached to the rods so all I had to do was assemble the engine. It takes the guess work out of things to get a little help.