LS3 block brand new from GM used for a 415 build. Only has about 130 runs on it since new. Has a crack right between cylinder 2 and 4. No leaking combustion and no water between sleeves. Sleeves are fine.

Can this be put back together? The head is off because the ported ls3’s broke through the floor of the exhaust on cylinder 8 and was leaking water.

I’ve searched and all the cracked blocks I’ve found cracked into the water jacket.

 

That's a tough one.

I would have to guess that there is not an issue in that area as far as coolant. Not sure you could do a surface weld next to the sleeve. Maybe some Epoxy could be used?

 

I agree...tough situation. Not what we expected to find starting with a brand new block. Engine has never been hot, spark plugs looked great, no signs of heat/detonation...just bad luck I guess?

I think it's either send it, or scrap it...just trying to figure out if this is actually a problem or not.

I haven't been able to find any other documented instances of a crack in this area. I've seen plenty cracked into the water jackets and that definitely is a problem.

 

If I had to guess, I would believe it has to do with the expansion and contraction rates between the block and the sleeves wing dissimilar metals. I dont believe there is anything you could have done or did do wrong.
I have an early gen 3 aluminum block like this. I wanted to see if i could use an aluminum brazing technique to fill in the void after grinding it out. In my case, the block needs machine work any way so I wouldn't be concerned with any distortion issues. They either use propane or MAP gas to melt the aluminum brazing rod. In the demo, they welds 2 aluminum soda cans with it using only this special rod and a propane style torch.

I still think you could send it like that. It obviously didnt have an issue before you found it on tear down.

Wish I could be more helpful or provide a better answer.

 

Engine builder friend of ours says send it! Worst case it loses a HG and it needs to be fixed. Right now it showed no issues since it isn't into water. The HG is sealing on the sleeve and not on the aluminum deck since it is stock bore and not a huge gasket. It shouldn't pose an issue.

 

Glad to hear! ​​​​​​​

 

I am wondering if a tiny smidge of the copper spray tach head gasket stuff might help here. Just in the crack area to maybe help fill in things to make it level with the gasket. Maybe a machinist or engine guy can chime in here. I know on the MLS stuff sometimes they want nothing on it.

 

I reached out to Steve at Race Engine Development who resleeves all kinds of blocks.... here is his reply:
http://www.raceenginedevelopment.com/

I would leave it alone and run it. It is nearly impossible to weld the block up between the bores and not have it crack again alongside the weld. It may last forever the way it is.
Put three tablets of "GM Coolant System Sealer" in the radiator to seal it. There is no way to tell how far down that crack extends.
I have had a few of these LS3, LSA, LS9 blocks come in with the opposite issue, cracked sleeves and the block is OK. Those are no problem to resleeve.

 

Mark thanks a lot man! I didn’t want to bug Steve because either way we wouldn’t have sleeved it.

Also talked to an engineer from Fel Pro and everyone is in agreement to just send it.