Low Compression New Motor

[aspekt9]

My new motor has 1800 miles on it. I did a compression test last week and it was at 180 175 175 180. I attributed the difference to it still breaking in a bit. I went to do some pulls today in 3rd gear not realizing my boost controller was messed up. I ended up hitting almost 30PSI on the 14b, according to link my INJ Duty cycle was 137% and that's when it happened. The car just kind of fell on its face when I slowed down and came to a start. It wouldn't idle at all. I pulled over and I did a compression test right there in the parking lot. 155 90 155 155 was the result. I then put a cap full of oil in and got 180 90 180 180. Now I'm running an MLS headgasket and the deck and head were both surfaced for one but I had been having some sealing issues with it. I retorqued the ARP head studs and it seemed to fix the issue. According to link I had ZERO (0) knock retard during the whole ordeal, so I don't see how detonation could have been a factor unless my knock sensor is busted? Going by the results and increased numbers during the wet test lead me to believe that its the rings, but I don't understand, what exactly could cause the rings to do that? I'm running 2g pistons, 1g rods and hasting piston rings gapped to .020/.024. I noticed the breather tube from the valve cover was blowing out smoke, couldn't tell if it was exhaust or oil burning. Where do I go from here? I'm thinking it's definitely a headgasket issue but is it possible my 1800 mile motor needs new rings? I've also been running rich at WOT but i don't think a difference of 4 days I would see that big a drop in compression if fuel was washing down the walls. I haven't really been wide open throttle a lot.

 

[Colt4G63 also]

Sorry to say, but it sounds bad. I don't think your knock sensor was working either.

 

[aspekt9]

So I pulled the motor out and tore it down. I took off the head and inspected the head and block. I couldn't find any issues with the head, the valves all looked fine and the surface looked okay, it had residual copper from the copper spray but other than that it was clean. The deck was the same way. The top of the pistons had a little bit of black on them but appeared to be in one piece. I rotated the crank it was REALLY easy to move, so my rings are definitely trashed. The walls had a visible cross hatch but they were as smooth as silk. I'm guessing maybe running rich washed the cylinder walls down and wore the rings down too? I still don't know why there was so much a drop in cylinder too, perhaps I'll know better when I take the pistons out. I put my finger in the bore and moved it around and I could feel a little bit of an indent on one place near the top of the cylinder where the ridge forms, it was present on all cylinders, maybe the rings butted or something? So where do I go from here? Will I need to bore the motor or could I get away with a hone? If I need to bore it I think I'm in trouble because the 2g pistons are only made in .020, right? The rods should be reusable and if I only need a hone maybe I can get away with reusing the pistons as well. I could also have cracked a ringland on #2 as well. What's the easiest way to get the flywheel off when the crank pulley and bolt are already off? Here's some pictures:

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[viprez586]

Sounds like something shit the bed, tear it down again. Your machinist will tell you if its a bore or hone situation.

3/8" Impact works for me when taking off flywheel bolts.

 

[aspekt9]

Yeah I took an impact gun to it, got them right out. I'm going to pull the pistons out tomorrow night and see whats up. If the pistons are fine and the block just needs a hone would I be able to run the same pistons or would I need bigger pistons since the PTW clearance would then be off? (I had them go .002 originally).

 

[viprez586]

Honing takes very little if any material away. You'll be ok if all you need is a hone.

 

[aspekt9]

Is it likely running so rich at WOT wore the rings down that much that the motor was so easy to turn over by hand? I'm trying to avoid this from happening when I put the motor back together. How can I verify the headgasket is in okay shape? What do I look for?

When I put the motor back together I'm going to put in a brand new knock sensor and tune my WOT and try to target 11.0:1. Is there any way to test the knock sensor is connected properly? Can I perform a leakdown test before running the motor for the first time to verify everything is sealed up?