LS3_Alex

Blew motor in my ysi ls3 vette and now in a situation. I will be needing to replace at least the passenger head on my ls3 to swap over to any block. My block has a hole between pistons and wall is gone I was told it could be sleeved but with the pricing I could get my hands on a 5.3 gen IV for $750 or do a tsp 429 short block. I just don’t want to blow a $7000 short block I may be paranoid. Should I go with the 5.3 or do a built short block?

Spaceme1117

Could you share some details on what happened?

LS3_Alex

I had a 3.1 8 rib pulley on my ysi I started to lift my heads as it was building pressure in my coolant system. So I got rid of the stock stuff and added arp studs and ls9 gaskets and a 2.8 8 rib pulley on the ysi. I guess I didn’t do something right maybe didn’t clean heads correctly not sure but this was the outcome

harleyreb1

Did you have the heads re surfaced while they were off? If not I’m guessing the heads were not flat from being lifted before.

renegade123

Bingo ! If you did not have the heads resurfaced, you could have been working with an ever so slightly warped head to begin with. Good luck bro

LS3_Alex

Yes I am sure that’s what happened now I’m gonna do the 58x 5.3 and port whatever heads are on it swap over my cam do a melling pump swap over my studs and do ls9 gaskets again hopefully I’ll make some power

Unreal

Either way, a 2.85 on a Ysi is a 1100+rwhp pulley. Stock ls3, even with gaskets/studs isnt going to live there.

realcanuk

Bingo.

CRUSHAH

^^This^^

CI GS

But what else, other than 6 bolt heads, on a “forged motor” would’ve prevented that kind damage though? I mean, the pistons survived, it didn’t snap a rod, break the crank, etc., so it’s not the stock internals that failed. Or are we talking about the strength of the deck on the stock LS3 Head?
I would’ve guessed that it was too much ignition lead/not enough octane, and the exhaust valve glowed hot on that cylinder and that caused it. Because a bad tune up can kill any motor, right?
I also agree that if the head was warped from being lifted before, it could be that the gasket wasn’t clamped properly in that area and that’s what caused it to burn out between those two cylinders?
So, I guess I’m asking if the consensus is that this damage was caused by the heads lifting (or flexing) and if so, does that mean it’s necessary to go to a 6-bolt head setup above 1,000hp? Because it sounds like the OP is going to go with a built 5.3 using the same studs, etc. so he may not be out of the woods with that setup either.

realcanuk

Head probably just lifted. Can stay 4 bolt but an aftermarket head with a thicker deck is needed.

Unreal

The factory GM heads, like LS3 or LS7 flex and lift. It then allows a steam vent to start melting the block/head.

Yes, he will have same problems if he just slaps same setup on a 5.3. You can get a bit farther with LSA/LS9 heads as they are a stronger material, and thicker, but in the end you need a way to keep the heads down and on. When you get to 1000+ keep heads down and on becomes much more of an issue than piston/block/rod failure.

Same reason at 850+ stock ls7 heads fail like this all the time. They just can't hold the cylinder pressure.

CI GS

Okay, that makes sense to me, I wouldn’t dare try to push that kind of power out of my SBE/stock head setup. The LSA/LS9 long block, maybe, but not a stock LS3. I have to say that I’m impressed that the stock pistons and rods held up. I guess that’s probably a sign that he didn’t have detonation.

LS3_Alex

Crank rods and pistons are all fine. Just between those to cylinders I got the failure. I don’t think it was due to my tuner as it was on dyno being dialed in on the new pulley on the ysi. I was making 15psi with a 3.125 pulley on the ysi and still was running rich 10.9afr so I decided to do a 2.85 pulley and get it retuned but my tuner told me to do head studs and ls9 gaskets first but I did not resurface the heads which is why this happened. I decided to go with a tsp 418 short block and thinking of getting new ported ls3 heads.

Unreal

LS3 heads won't hold that power level. Same thing will happen.

LS3_Alex

Which heads do y’all recommend

Unreal

Anything with either a thicker deck or strong material. If you really want to run a 2.7 on a YSI, should be an aftermarket 6 bolt head. Mast, Brodix, All Pro, Trickflow, etc etc

Otherwise LSA or LS9 heads are a thicker deck better material and hold up a bit better, but may still have issues at that power level.

CI GS

The AFR Mongoose 260 head looks promising too. AFR uses virgin 356 alloy and the decks are 3/4” thick. It will outperform any of the GM castings on that size motor and has a bunch of options and features. The last time I checked, you could even get the 6-bolt version for about the same price as the 4-bolt version.

Unreal

6 bolt version is going to be the same, they just don't mill off the extra head bolt hole. No reason not to keep it there just for resale and future upgrades if you ever run a 6 bolt block.

CI GS

That’s my thinking on it too.