99pewterZ71

iTrader: (3)

I pulled my ported stock 243s off my LS2 to install a pair of LS3 821 heads for an LSA supercharger swap. My combo consist of a brand new LS2 block with forged -3.2cc Weiscos, forged stock length rods 0 decked with a stock crank. From the get go I had a few issues with crankcase pressure. I blew out the rear main and dipstick at the track. I upgraded the breathing of the PCV system and got it under control with a CFM valve cover breather and a vented catch can. I did a compression check and they all came back 180 psi and the leak down was 9-12%. Its now about 7500 miles later and I found vertical scuffing on the cylinder walls. I can catch my nail on a few of them on the #2 cylinder but the rest were smooth. A part of me wants to just say screw it and bolt the heads on and go,dealing with the pressure but the rational side of me says to pull it and see what the deal is. So what can cause this? Ive read about not deburring the ends of the rings, but I wouldn't think that all of the rings would be positioned in the exact same position on each piston. So piston skirts? Why? When the engine was assembled it came out of the plastic bag and the heads went on right away so dirty cylinders doesn't seem plausible.
I want to go into the machine shop with some sound theories and see about getting a little help from them. I have used them tons over the years but am not what they could have done wrong on a stock bore new LS2 block.
Here are the pictures




This is the same mark as above but with the camera flash which makes it look worse than it is. Its smooth to the touch.

GSAWYERS

The crankcase pressure, fairly high leakdown numbers don't sound too good to me. I've sprayed big shots on junkyard motors that were worse, but I didn't care about them. It could be a couple of different things causing the issue. Rings not being installed properly or some bad rings. Could be a piston to wall clearance issue. Maybe it's just me, but the cylinder hone looks odd, could just be the pictures or my vision playing with me. Either way, unless you can afford to trash a fixable LS2, I'd pull it apart and start checking things.

joyridin'

iTrader: (1)

You may want to get a dial bore gauge and check the diameter of the cylinders. You can also check if they are round. You also may want to pop a piston out and mic it up also to get a better picture of the clearance.

With only 7500 miles, it looks a bit rough.

RixTrix

I don't think you have a crank case pressure problem, you have a ring seal problem.
Unless you plugged factory venting or had mismatched parts.

This



Is no bueno.

It's been a while but, I'm pretty sure 9-12% leakage is in the bad zone.

Probably not related to your problem but - I see a lot of debris in the gap between the pistons and the cylinders too.

I would not boost it in this condition, I think you will have big trouble keeping oil in it.

A.R. Shale Targa

iTrader: (2)

The cross hatch does look a bit too coarse/sharp for a moly ring type application. That not only made it take substantially longer (miles) for the rings to take a seat, but also could have scuffed most of the moly off the edge of the primary ring in the process.
Your leak down numbers could point to the shop gapping the rings quite large to allow for boost or spray....figuring since forged pistons and all
The vertical scuffing is pretty common like that in a forged piston application where the piston to wall clearances are often 4-5 times that of a factory hyper piston. The piston rocks substantially more on directional change and Teflon coated skirts help minimize this but don't eliminate it.
The one hole merely shows stains from water or moisture in it pehaps from over winter or could point to a head gasket seeping when shut off.????
The best way to fix this, assuming you wish/need to have the forged pistons, have the block three stage honed (coarse/medium/fine) out to either 4.010" or 4.020".......run new slugs with the Teflon coated skirts, and run Total Seal Gapless rings. Not cheap but sealed up much better non the less.
The generic fix would be to slap your new heads on and run an air/evac pump to reduce the blow by crankcase pressure which only serves to cause oil leaks and flutters the rings further reducing the sealing ability/power

99pewterZ71

iTrader: (3)

I thought the same thing about the hone but im not sure what was required by the rings that came with the weiscos. Thanks, your last sentence about ruining an ls2 block helped me come to my senses a bit.

Will do, I agree. Im leaning towards a piston to wall clearance issue.

The leakage is not great but its not terrible either. Gauges can be off 3-4% even for a good new gauge (which mine was). It could be 7-8 or 15-16% Obviously with the amount of crankcase pressure that was being created it must have been high. The debris is just dirt and grime that fell into the engine when removing the heads. Thanks for the help.

99pewterZ71

iTrader: (3)

I would like to keep the forged pistons for the LSA blower. It makes sense that its just a stain from moisture I don't know how long it takes but it had a bit of coolant sit in there overnight after the heads were off. I thought I soaked all the water up but must have missed it. Im pretty sure my Wisecos have steel rings, is this still a bit course for a steel ring to breakin and seal? Are there any known problems running the gapless rings under a boosted application? Thanks for the reply.

KCS

iTrader: (20)

The scuffing looks pretty normal to me, I wouldn't worry about it. The crankcase pressure issue would worry me though. You shouldn't be blowing out rear mains or dipsticks in an NA car and the leakdown does seem a bit excessive. How is oil consumption?

If the time/money for a rebuild is not in your budget, I don't think it will hurt the engine to go forward with the swap so long as you vent the crankcase and stay on top of oil changes.

RixTrix

I wonder if there wasn't a timing or fueling issue that contributed to the problem.

If it was detonating that would easily explain the crank case pressure. Like if it was dyno tuned at WFO and part throttle was untouched. A part throttle tune is important for example in a burnout.

99pewterZ71

iTrader: (3)

Oil consumption was around a quart every 2000-2500 but it really varied with how hard I was on it. I switched to Penzoil synthetic and saw consumption drop considerably. When I blew out the rear main I did had all stock PCV components and I believe one line was hookedup wrong which contributed. I installed the mighty mouse catch can with a breather and it would still pop the dipstick out every so often so I got the CFM breather that fixed it all. The pressure was never bad enough to blow smoke out of the breather with the cap off just revving it in the driveway or letting it idle.

I did all my own tuning and tuned for 0 knock. It wasn't an aggressive tune and part throttle WB readings under load were usually in the low 13s or high 12s and WOT was 12.6ish. The plugs never showed any signs either.

A.R. Shale Targa

iTrader: (2)

Speed Pro Hell Fire rings are steel as well but they still have a moly facing which during break in conforms to the bore/cross hatch. This process is the seating of the rings and ring seal is everything. Any good dyno operator will tell you that engines will make more power when they are loaded/lugged on the water brake during these critical first moments of ring conformity. The resistance to motion (loading) causes heat build up and the air pump works which pressure forces the rings into the cross hatching. Better seal=better power.
This is something that the common man does not always have access to do properly.
This is why I scream from the roof tops about using Total Seal Quick Seat powder on freshly honed bores....cleaned and DRY
With a simple shop light you can see the bore/ring conformity taking place during assembly. Literally watch the cross hatch (if properly matched to rings) change to the visual naked eye. Still not as good as a dyno session but better than just ordinary oil or Dexron fluid.
IMO if you run gapless rings(second not primary) properly gapped they will work fine in a forced induction application......however if the boost is too much for the timing/tune then the rings will undoubtedly become one of the weak links in the system

99pewterZ71

iTrader: (3)

Thanks for the input. If I rering it then I will talk to my machine shop about using the total seal quick seal powder. I just went and looked at my original block that I had sitting in the barn at my parents and it actually had similar marks but not quite as much and it had 70k before the pressure plate blew up and took out the block.