Need block suggestions! Having issues

Engine specs as of last build:
-Thompson Motorsports 5.7l (Refurbished seasoned 5.3l)
-72mm Magnum turbo
-TU1 Custom Grind cam(spec speed.inc)
-799 heads
-GM MLS head gaskets
-ARP head bolts
-.660" Trick Flow dual valve springs
-Titanium retainers & locks
-7.400" Comp Cams Chromoly Push Rods
-LS7 lifters
-5.3l(LM7) rockers
-Forged Probe Pistons 3.902" flat top
-TMS Moly rings
-4340 Forged scat I-beam connecting rod w/ ARP 8740 rod bolts
-King racing bearings
-Melling high pressure relief oil pump
-TR6 spark plugs
-"Muscle Car" oil pan
-All other parts are stk 5.3l(LM7)

So here's the story:

Block #1: 5.3l out of a 120,000km 2001 Silverado
Get on the dyno and after several weak pulls it starts venting bad. Pull the head Cylinder number 5 had a broken piston. After further inspection multiple pistons had cracks between the ring slots.

Block #2:Thompson Motorsports 5.7l(bored from 5.3l) engine(The one described at the top of this post)
Runs for about 15min while on the highway. I started accelerating going 130kmh with 5lb of boost. Engine locks up and wont turn over. Pull the block out- 3 cylinders cracked to the waterjacket, pistons are wedged in cylinder bore, and most of the rods are bent.(no damage on the gaskets or the head really, although the heads show signs of detonation.

Block #3: Get warranty Thompson Motorsports 5.7l(bored from 5.3l) engine back
Tried installing cam but it was very tight. Turns out the cam was bent from the last engine blowing up. Decide to get the whole thing gone through. Fix the cam, but the sonic test determines that the cylinder walls in some spots are .140". After doing some research a lot of people say it's ok for NA but not for boost(i plan on going up to 18lb).

Additional info: Most parts have been reused several times now. I have used new head gaskets every time and got new head bolts as well.

So: I have the first block still with some scoring in the cylinders and a freshly sandblasted lq4. What do you guys recommend I do? I am willing to buy a different block if need be, but if either of these could be used I would like to go that route.

Any help would be greatly appreciated!

I can post pictures if need be

what caused the first tms engine to lock up? im dealing with thompson right now and having some issues myslelf...

What I am thinking is that the walls were too thin to begin with and with the light boost it split. They said they had no idea why it would break that bad but the only thing I can come up with is really thin walls. My engine builder wants me to go to a 4.8 just for the wall thickness to get a bulletproof setup. Ive already spent about $16000 on this project and I'm pretty sick of it. I am glad Thompson gave me a warrantied engine but when I sent it back they kept my head dowels($22 in Canada for 4) and they didnt clean out my oil pump or give me a new one. I pulled it apart myself to get the particulate out. Im really not too pleased

And to top it off I'm stuck with a $3500 short block that I cant boost

yea that sucks. The 5.3 and 4.8 use the same block. The 3.902" is the pushing it on the 5.3 block imo. Iv always ran a 3.89" (factory ls1 bore size) bore when i punch out a 5.3 block and never had any problems

Hmm, so do you think I should do the iron 6l or bore out my scored 5.3 to 3.89"?

Do you already have an iron 6.0?

You probably could of built a 370 or 408 for what the iron 5.7 cost.

Plenty of ppl made power with a iron57

TMS may just not have their A game going on
Also you get what you pay for..if a motor price is too good to be true it probably is

I wouldn't run a TMS motor

Quote:

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Originally Posted by chvy=power

Do you already have an iron 6.0?

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Ya I have it. Its been blasted so Ill do a slight bore and go from there. Neil @ Horsepower Solutions up here is telling me that its the way to go, considering he's got one of the fastest quarter mile LSX cars out there I'm gonna take his word for it haha.

Well its a little late not to run the motor haha. And as far as getting what I payed for goes, I've heard similar stories from guys who have bought LSX blocks and had similar problems within 10 min of running it.

Quote:

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Originally Posted by George C

Plenty of ppl made power with a iron57

TMS may just not have their A game going on
Also you get what you pay for..if a motor price is too good to be true it probably is

I wouldn't run a TMS motor

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+1

I'd say run the 6.0 no doubt

Thanks for you input man, really appreciate it. Hopefully no issues this time around haha

Quote:

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Originally Posted by shmiet

Well its a little late not to run the motor haha. And as far as getting what I payed for goes, I've heard similar stories from guys who have bought LSX blocks and had similar problems within 10 min of running it.

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if referring to me having a lsx block... its come bare and needs tons of machine work. so statement of having a lsx block fail would strictly be due to the builder

TMS is a budget builder with budget results, ive seen enough from them to not deal with them

Apologies for the misunderstanding, but no I did not say that because you have an LSX. I didn't even read your sig until just now.
I was referring to an off the shelf short block. Keep in mind that even 6 sigma companies still make bad product that hits the shelves.

Quote:

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Originally Posted by shmiet

Apologies for the misunderstanding, but no I did not say that because you have an LSX. I didn't even read your sig until just now.
I was referring to an off the shelf short block. Keep in mind that even 6 sigma companies still make bad product that hits the shelves.

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not ordering a motor from those internet famous shops

Well I'm 20 so I still got time to make mistakes no? haha

Quote:

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Originally Posted by shmiet

Well I'm 20 so I still got time to make mistakes no? haha

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being a 20yr canuck youre mistakes are fine lol

i killed a stock 6.0 and ended up going with an AES 390, working out pretty good so far, just got the money flow to finish the F1-a setup and new fuel system so no idea on #s yet but they are many people making 800-900+

Quote:

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Originally Posted by shmiet

What I am thinking is that the walls were too thin to begin with and with the light boost it split. They said they had no idea why it would break that bad but the only thing I can come up with is really thin walls. My engine builder wants me to go to a 4.8 just for the wall thickness to get a bulletproof setup. Ive already spent about $16000 on this project and I'm pretty sick of it. I am glad Thompson gave me a warrantied engine but when I sent it back they kept my head dowels($22 in Canada for 4) and they didnt clean out my oil pump or give me a new one. I pulled it apart myself to get the particulate out. Im really not too pleased

And to top it off I'm stuck with a $3500 short block that I cant boost

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Your engine builder doesn't know the 4.8 blocks are the same as the 5.3... not much of an engine builder.

you skimped on pistons, you skimped on the block... what do you expect?

I miss interpreted what he said, he meant they can handle boost better than the 5.3 due to the stroke.

I expect failure, cause I'm dumb eh.