Today's find

[SS_Dave]

So I was under the car today and found something that really didn't excite me. Now I recognize probably no one can give a good definitive answer without seeing it in person, or at least some pics. And pics are hard to get in this situation. So this may be more venting than anything.

In short, it seems like there is an oil leak where the heads meet the block. Heads are clean from that seam up, but from the seam to below there is leakage. Basically from about halfway back, toward the rear it progressively looks bigger. Kind of an increasing angle of more oil blow by as you go back toward trans.

Now I'm also ready for a clutch and planning for the rear main. I suppose it could be blowout from there, but with the pattern, I seriously doubt it.

Note, oil changes and dipstick have always been very clean. No water or contaminants in the oil. Also valve cover seals were done recently and it's clean from them down. Wetness starts at seam between heads and block and only halfway back. Oil pressure shows good.

So, this has me thinking. If I have to pull the heads to fix this, then I might as well be going back together with upgraded parts and get some improved performance out of it. That has me debating price vs ROI if fixing and improving the stock LS3 vs something like building a new 416 or whatever to replace and just sell this motor. It runs perfect. And after tune and headers dyno'd last year at 424HP/421TQ.

[1JEWLDSSRS]

That's a funky one. How about the possibility that the rear of your valley cover might be leaking?? And the crankcase pressure is pushing it out there. Maybe? Or your oil pressure sending unit?

[SS_Dave]

Originally Posted by 1JEWLDSSRS

That's a funky one. How about the possibility that the rear of your valley cover might be leaking?? And the crankcase pressure is pushing it out there. Maybe? Or your oil pressure sending unit?

That may be a possibility. It's really hard to see, but looking back there, it looks like the top of the bellhousing on the trans is messy, so maybe it's leaking there, dripping down and around and has only accumulated enough to soak halfway forward on the heads. Still weird and not sure about that. But it would be a lot easier to fix.

And is there a PCV somewhere I'm missing that could be a contributor?

[1JEWLDSSRS]

Originally Posted by SS_Dave

That may be a possibility. It's really hard to see, but looking back there, it looks like the top of the bellhousing on the trans is messy, so maybe it's leaking there, dripping down and around and has only accumulated enough to soak halfway forward on the heads. Still weird and not sure about that. But it would be a lot easier to fix.

And is there a PCV somewhere I'm missing that could be a contributor?

Yeah, pressure from the crankcase could blow out the valley tray gasket, I have seen that. If it were a rear main seal it would be on the bottom of your bell housing dripping from the small access cover for the flywheel. As for the PCV you asked about, the only PCV system out LS3's have from the factory, depending on what manifold you are running, stock the hose from the nipple on the front of the valley plate goes into a nipple behind the TB on the manifold, passenger side valve cover the nipple on the back top of it the hose connects to a fitting on the air intake tube behind the MAF, and before the TB. That hose supplies clean air through the head into the crankcase, the driver side valve cover nipple on the back is capped off from the factory. And from what I have researched, that is GM's "efficient" PCV system.. According to them. I run a valve cover breather with a check ball in it to help keep the crankcase pressure under control. It lets pressure out, but no "unmetered" air in. Another thing that could be making it leak, the valley tray, is that the rear bolts may have loosened a bit. They usually seal pretty good, but they could possibly vibrate lose just enough to seek under pressure. Especially if it is on BOTH head seams..

[SS_Dave]

So based on seeing some residue on top of bell housing, I'm kind of thinking that its just collecting and running across the seam at heads and block. And it's just heavier in the back because that's where it accumulates and less in the front because it pushes forward when setting. (Only 2k miles on this car in the last year). So assuming it's valley cover, this has me thinking about doing it myself and ROI of other items along the way.

To me, it looks like I only have to pull throttle body, fuel rails and intake to get to it. Anything else would be in the way? And while I have them off, I'm thinking of full cleaning and flow test of injectors and rails. Or is there any real value of any kind of upgraded injectors on a stock motor? Also, on the intake any real value in having like GPI port and/or rod mod done? Basically trying to think of what holds real value in putting things back together best as possible without spending a fortune given it's a stock motor with 114K miles on it.

Also looking for good process videos now to get comfortable with the process.

[morepowerjoe]

Originally Posted by 1JEWLDSSRS

Yeah, pressure from the crankcase could blow out the valley tray gasket, I have seen that. If it were a rear main seal it would be on the bottom of your bell housing dripping from the small access cover for the flywheel. As for the PCV you asked about, the only PCV system out LS3's have from the factory, depending on what manifold you are running, stock the hose from the nipple on the front of the valley plate goes into a nipple behind the TB on the manifold, passenger side valve cover the nipple on the back top of it the hose connects to a fitting on the air intake tube behind the MAF, and before the TB. That hose supplies clean air through the head into the crankcase, the driver side valve cover nipple on the back is capped off from the factory. And from what I have researched, that is GM's "efficient" PCV system.. According to them. I run a valve cover breather with a check ball in it to help keep the crankcase pressure under control. It lets pressure out, but no "unmetered" air in. Another thing that could be making it leak, the valley tray, is that the rear bolts may have loosened a bit. They usually seal pretty good, but they could possibly vibrate lose just enough to seek under pressure. Especially if it is on BOTH head seams..

Hey buddy if you have time you might want to read this article https://www.shophemi.com/images/medi..._ccv_bible.pdf it clears up a lot of confusion for the pcv system.

And to the oil leak. There wouldn't really be any oil leaking from the head because there is no oil under the head unless you have a blown head gasket and which you would have a coolant leak if anything. It could be coming from the valley cover like Wayne was saying because I actually had a leak there once. Thay's probably where it's coming from.

As far as upgrades, there's no use and upgrading the stock injectors on a stock engine until you get over around 500 whp. I will say that I did upgrade my valley cover though with a ICT cover and it is a high quality piece.

[Joe.G]

I do recommend the Ported Rod mod intake, there was a noticeable difference after the swap, If you are pulling it off I would do it.