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Discussion Starter · #1 ·
OK, After hours of trying to track this down I wouldn't believe it if I hadn't felt the air leaking out with my own fingers. When I pressurize the system by blocking the intake with a soup can, I have tracked the boost leak to....where the main oil return attaches to the upper oil pan. Stock twins with about 8000 miles on the entire engine including turbos.

A. Is this bad? I mean, I can loosen the two bolts and coat the gasket with FIPG.
B. How does charge air in the boost system get to there? I know the sequential system well and this blows me away. I must be missing something.
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blow by .... rings are worn out
 

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Slo-vertible Drifter
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So to clarify you are pressurizing the intake and losing pressure out the oil return system. That's not right.
 

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My guess is bad rings...pressure is filling the cylinder during your boost leak test, then going straight past the rings and into the crankcase, and the pressure is escaping through the oil return. At least this would be my guess...
 

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Be sure to block off the Vent from the Valve covers to the twin piping (there is no valve here). Also check to make sure your PCV valve isn't bad as well (to the intake manifold).
 

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I had the same problem on a fox mustang.
Installed new supercharger on hi mileage motor.
Started the car for 1st time, revved it, and blew out the oilpan gasket.
Boost got past old worn rings, pressurized oil pan and that was that.
 

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Proud MKIII Owner
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I had the same problem on a fox mustang.
Installed new supercharger on hi mileage motor.
Started the car for 1st time, revved it, and blew out the oilpan gasket.
Boost got past old worn rings, pressurized oil pan and that was that.
That's exactly what I meant in my original post, just in simpler terms.
 

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Be sure to block off the Vent from the Valve covers to the twin piping (there is no valve here). Also check to make sure your PCV valve isn't bad as well (to the intake manifold).
This might very well be what's going on. Make sure to plug all those PCV lines and such, and try again.
 

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Discussion Starter · #9 ·
Be sure to block off the Vent from the Valve covers to the twin piping (there is no valve here). Also check to make sure your PCV valve isn't bad as well (to the intake manifold).
Thanks for the replies. I'm thinking this is the issue. I'm going to re-try the test with this capped and see if the results are different. Motor is strong and is only a year old top to bottom. Reason for all of it is that I discovered my sequential issue and wanted to do a boost leak test prior to hooking up IACV/EGCV and really stressing all the event timing.
 

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Discussion Starter · #12 ·
Same result with exhaust cover valve and PCV intake inlet plugged. I'm definitely going to do a compression test to see if everything with the rings is normal. The engine has good response and torque. I just can't see how there is a significant issue with the piston rings. I'm not saying there isn't, it just doesn't add up in my brain.
 
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