Hey guys, just looking for advice from anyone who's done a 5.3 to 5.7 bore. My block is at the machine shop with the intention of boring to a 5.7, but my machinist is telling my he wouldn't do it to his own engine, and stating I'm going to have over heating and longevity issues due to the cylinder walls being less than 1/8" thick. It was Sonic tested and he says it can be done but he doesn't advise it. I have however read on this and other forums that people have been successfully doing this for some time now with no issues. Can anyone tell me what their 2 cents is and what I should do? I'd rather not achieve the extra displacement with stroke, as it's going to cost $$$ for a new crank, rods etc.

2010 Tahoe
Stock 5.3, 799 heads
4.56 gears, 35" tires
CAI, headers and underdrive pulleys
Texas speed stage III cam
Blackbear tuned

This vehicle will be a daily driver but not driven daily. We have other vehicles we use on a daily basis. Tahoe will be used for family trips and towing my 24ft boat to the lake a few times per summer.

If I move forward with the bore, is there anything I need to do to the heads for more flow? Larger intake valves etc?

I am also attaching the Sonic test results for your review.

 

Typically they want you to have around .200 of minimum thickness around the bore to be safe. Some say no less than .150 minimum wall thickness.

Part of this is because the back sides of the cylinder's are rough from the casting. You can not see the porosity or how deep it is.


If he says 1/8 that is .125

Factory 4.8/5.3L bore is 3.780
factory 5.7L is 3.898

Difference of .118 total so that would be .059 off the side

That being said, This has been done a lot in the LS world. There have only been a handle full of blocks that have been too thin or the castings were shifted so much it bored through the cylinder.

 

So given the information provided and your experience would this be safe to do on this block? Or should I go with a bit smaller of a bore to stay closer to .150 wall thickness? I see what you're saying but it appears a lot of people are doing this with no issues, despite what the information is telling me. I just don't want to be replacing the bottom end less than a year from now.

Or would it be safer to just pick up a 5.7 short block and do some work on that? Problem is I'm already in it some $$ for having the 5.3 block cleaned and sonic tested.

 

I myself have not done it, Although the thought crossed my mine. I find it interesting that it's only the center 4 holes on the block that are thin.

I am not sure what else is available for pistons other than a .060 over bore or going to a 5.7L piston. If I did a 5.7 It would be a standard bore piston.

I wouldnt have a problem doing an iron 5.7 But the cost of multiple blocks to find one that would meet my expectations would be cost prohibitive.

 

I spoke to the guys at Texas Speed this morning and they're confirming what my machinist is saying. Those 4 inner cylinder walls don't have enough meat on them to do the 5.7 bore. Day ruined. So I said let's find a happy medium and go .60 over......found out the biggest pistons available for that year and block are .40 over. Day REALLY ruined.

 

I have built numerous iron 5.7s with no issue. I use a 3.898 bore size. We have those pistons in gen3 press pin and gen4 floating pin.
I would build one if i had a 4.8/5.3 truck but all mine are 6.0.
383s use 3.898-3.905 pistons and quite a fe of them around also.

 

I bored my aluminum block 5.3 to 5.7 unfortunately have not installed it yet so no idea if it it will survive or not. Cant wait to find out.