Sorry for the odd question, but how common is it to have a cracked block or head in a LS1? uoa shows coolant in oil, very little, oil looks fine, no combustion gas in radiator, loses pressure very slow with coolant pressure test. called one sponsor from here they told me most likely not a head gasket but a cracked block or head and with that little coolant in oil just to drive it till it crack lets go, engine has 20k on it stock heads have been cnc ported and milled .020, I'm kind of confused should I have heads pulled and checked and replace head gaskets or pull engine and have the whole thing checked out. what would the chances of it just being the gasket?

 

you said that it had very little coolant in the oil. if you live in a colder place you will get condensation in the oil (most commonly seen on underside of oil fill cap). if you dont run the vehicle for more than a few mins, or let it sit for the winter while only starting it for a couple mins you will get more of a build up of condensation. i would change the oil and drive the car for 20+ mins and recheck the oil when the car cools off.

just my 2 cents

 

Dont have any condensation, oil looks like new and nothing under cap uoa shows very little coolant in oil, thats why I'm confused really no signs of leak other than slow drop in coolant system pressure test

 

It could be a gasket, kinda weird. Its not a common problem on these engines, they are actualy known for their engineering advancements. Of course with abuse all that means nothing.

 

ha...just pullem. funny you posted this. im in the process of my new build but im using my old heads to mock up, the heads were off my last n20 combo but nothing crazy. i ended up going turbo when i had the same problem.

BUT 2 days ago my buddy from the shop showed me a crack in the head i over looked and i guess its pree common with these heads?

check the right side head where the bolts go through the center of the head....theres a little milled spot where the washer part of the bolt makes contact, look just to the right of there and theres a casting mark....mine cracked in there...they were p/p 241s


or just maybe a head gasket...

 

I was using Mobil 1 and it looked like there was some green coolant in it when I pulled the dipstick.... I had flushed my coolant and was using the universal coolant that was green so I was sure I had bad heads or gaskets. Turned out that I spoke with someone at Mobil 1 and they said there oil can have a green tint that looks like coolant about 1-2k miles after oil change. As a claims adjuster I have seen some ls1 blocks that were bad and it usually always happens at low mileage and for some reason mostly corvettes.

 

Go get some good sealer pills and drop them in. GM sells them and so does bars leak etc.

This is very common with aluminum engines, small porosity in the block. Its nothing to worry about.

 

Same exact thing happened on my stock 98' motor.. Pulled valve cover to replace the gasket on the passenger side head & saw just a lil bit of anifreeze pooling in the center of the head. It's more common on a specific 5.3 casting, can't remember which # though.

 

Talked to the shop that built the engine and to Texas speed both said the same thing don't tear it down and drive it, with 483ppm of sodium in oil thats to little to worry about also the lab that did the uoa said sodium and potassium could have been picked up from my trunion upgrade I did just before I sent sample in from the lube that was in trunions from the manufacturer.

 

I am only adding this as it refers to your original question. A friend of mine on here who I helped put his car together lost an LS1 block. It was not the block that cracked, but the sleeve. The car very slowly over time was losing coolant and getting hot after long drives. He pulled the heads and changed the gaskets. The over heating got better, but the coolant was still disappearing slowly. He pulled the heads again and found a crack in the top of the sleeve about 1.5-2" long.