Hello everyone! I've lurked on here quite a bit over the years, but never had a need to post up.

I recently finished building my very first LS3 motor, and am having some issues with it and looking for some guidance.

When first getting the motor going, it was blowing oil out the dipstick tube. I revised my venting and that seemed to stop it blowing out of the dipstick tube. Right now it's plumbed like this: intake valley to catch can to PCV, then a breather on each valve cover. The passenger side valve cover has a huge breather on it, and as soon as the motor warms up you can see "steam" coming from it. I'm assuming this is oil mist.

I thought maybe a ring issue, so I went ahead and did some tests. I did a compression and leak down tests and got the following results:

From the front of the car:

Drivers Side Passenger Side
185(15%) 160(25%)
190(18%) 140(23%)
150(15%) 145(24%)
150(19%) 130(23%)

The number represents PSI for the compression test and the % represents the leak down. 185 at the highest to 130 at the lowest does seem a bit much, but the leak down sure doesn't seem to be showing any signs of bad rings.

Any ideas or anything else I can try? Honestly I'm not even sure what to test next. The motor did "burn" oil, almost 4 quarts while on the Power Tour. I don't think it's burning it though, I think it's getting evaporated out the breather. All the plugs were spotless.

At this point I'm scratching my head wondering what else it could be. If you guys have some suggestions, that would be greatly appreciated.

 

What do the plugs look like?

 

Passenger side:


Drivers side:


Heres one plug on the passenger side that did look a little dirty compared to a clean one. That cylinder had 145PSI on compression and 24% leak down.

 

Were the bores torque plateed when honed or bored? My 6.0 appoy block had a 6thou taper on cyl #1

 

Yes they were, forgot to mention that.

 

How many miles on it at this point? maybe the rings haven't seated yet on all cylinders ?

 

About 4500 miles or so.

 

Are you doing the compression test corectly? All your #'s look low. Disabled the ignition, pull the fuel pump relay, pull all the plugs, prop your throttle plate open and crank each hole 10 secs. Then do it again with 2 squirts of oil in the plug holes and see if the psi increases. Better if the motor is near operating temp. If psi increases then of course you have ring issues. Use a known good tester.

 

I didn't do all of those steps. I'll have to redo it now that the car is back from another show.

I did talk with a company and they think the rings never set properly from start up and it probably needs to be taken apart, rehoned and put back together with a fresh set of rings. I would lean that way as well.

Just gotta find the time and money to make that happen now!

 

What type of oil did you use for break in?

 

Royal Purple's Engine Break In Oil

 

Rings seat almost instantly, especially after 4500 miles

Blow by is caused more by cylinder roundness vs the rings themselves

 

Agreed....something isn't right for sure. Just have to tear open the motor and take a look and see, I was just hoping to get some sorta direction before doing so.