piston ring failure?
Thread Starter
Launching!
Joined: Dec 2005
Posts: 232
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From: nj, edison
piston ring failure? what exactly are the properties and symptoms of ring failure in a stock ls1?
besides dismantling the block, what are some steps you can take to find out?
the reason i ask, is because i have been blowing my diptstick out ever so slightly, spraying from 100-150 shots. i stil have the stock pvc with a recently added home made catch can.
the motor seems fine, my mph have not dropped at the 1/4. i also pulled 15hg steady vacuum at idle. just recently performed a compression test and the results were suspicious but outstanding. 82kmiles on the engine with lots of 1/4 passes. so far this season, i have 28 on 100w no progression and two 150w no progression.
engine was idled to 220f and stopped at 4 pumps going by the gauge.
8,6 195psi , the rest were 200psi. should i continue to pummel the motor? it's not my daily driver.
besides dismantling the block, what are some steps you can take to find out?
the reason i ask, is because i have been blowing my diptstick out ever so slightly, spraying from 100-150 shots. i stil have the stock pvc with a recently added home made catch can.
the motor seems fine, my mph have not dropped at the 1/4. i also pulled 15hg steady vacuum at idle. just recently performed a compression test and the results were suspicious but outstanding. 82kmiles on the engine with lots of 1/4 passes. so far this season, i have 28 on 100w no progression and two 150w no progression.
engine was idled to 220f and stopped at 4 pumps going by the gauge.
8,6 195psi , the rest were 200psi. should i continue to pummel the motor? it's not my daily driver.
Thread Starter
Launching!
Joined: Dec 2005
Posts: 232
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From: nj, edison
so how would a bad ring show up? would the cylinder leak quicker than the rest? might as well ck. the low ones first, right ?.
thanks for relplying.
You dont need a big compressor to do a leak down test. When you do a leak down test turn the radio off and listen for the leaking air. Pull your oil fill cap off and see if you have air coming out of the crank case for bad rings. If its coming out of the intake or exhaust you have valve problems. If your coolant is bubbling you have bad head gaskets or a cracked block.
You dont need a big compressor to do a leak down test. When you do a leak down test turn the radio off and listen for the leaking air. Pull your oil fill cap off and see if you have air coming out of the crank case for bad rings. If its coming out of the intake or exhaust you have valve problems. If your coolant is bubbling you have bad head gaskets or a cracked block.
Thread Starter
Launching!
Joined: Dec 2005
Posts: 232
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From: nj, edison
i'm expecting to have leakage at the rings. like the compression test, if they all leak the same or close within what %?
i've read so many threads of guys blowing their dipstick out with fi or n2o, with relatively fresh engines on stock stuff.
i'm gonna do the leak ck. but, if my compression ck. came out ok. assuming the valves, gasket, block, and vacuum are ideal, shouldn't i expect similar results or is it possible to have good compression and say 40% leakage?. thanks a lot for discussing this with me guys.
i've read so many threads of guys blowing their dipstick out with fi or n2o, with relatively fresh engines on stock stuff.
i'm gonna do the leak ck. but, if my compression ck. came out ok. assuming the valves, gasket, block, and vacuum are ideal, shouldn't i expect similar results or is it possible to have good compression and say 40% leakage?. thanks a lot for discussing this with me guys.
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FormerVendor
Joined: Nov 2001
Posts: 3,065
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From: Houston, Tx.
You might have a small hole in a piston or some stuck rings with any NOS use at all so you can find out pretty quick with a leak down. A compression test will also show something if you are way off as well but leak down is probably a lil better.
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Verdad Gallardo Thread Starter
Launching!
Joined: Dec 2005
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From: nj, edison
so hypothetically, if i have a small hole or damaged ring{ stuck ring}, wouldn't i be down in power, and wouldn't it show up on my trap speeds? i have a scope that i used and did not see any obvious abnormalities in the top of the pistons.
Thread Starter
Launching!
Joined: Dec 2005
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From: nj, edison
another small bit of info on the engine, is that i have been doing it for quite some time. ever since i began spraying 100 and the 150. the dipstick comes out just a little, not shooting all the way out.
i have been logging and tuning very concervative. the engine took 28 passes with a 100w no progression this season and a couple of 150w so far. i mean if i had a vacuum pump, wouldn't the the trap speeds be my first clue?
i have been logging and tuning very concervative. the engine took 28 passes with a 100w no progression this season and a couple of 150w so far. i mean if i had a vacuum pump, wouldn't the the trap speeds be my first clue?
FormerVendor
Joined: Nov 2001
Posts: 3,065
Likes: 6
From: Houston, Tx.
If you aren't down much on power or anything else then you might just need a better breather system and maybe back off the timing a bit. Detonation puts way more pressure in the crankcase but these aluminum blocks are not all that so you may just have normal blowby for that engine when spraying.
Thread Starter
Launching!
Joined: Dec 2005
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From: nj, edison
If you aren't down much on power or anything else then you might just need a better breather system and maybe back off the timing a bit. Detonation puts way more pressure in the crankcase but these aluminum blocks are not all that so you may just have normal blowby for that engine when spraying.
i have always used my low oct. table as my back up so kr attack kicks in hard. so generally speaking, if i keep the afr at around 12 inital and kreeps down to about 11.2 with 18* trap speeds are normal. i'm just looking to spray the 200 once or twice and call it a day. the more info i get on the state of the engine will give me a fatter learning curve.
i know you set up a few guys with a 396, right?. i'm just a street strip guy. i figured a 376 ls3 would be my next small step.
A small 5 gal compressor will work and you dont have to buy a gauge either. Set the piston at TDC and perform a leakdown. The compressor should have a regulator, just set it around 40 psi at first then start moving it up until you start hearing a leak. Since you have the compression tester, just remove the schrader valve from the end of the hose and hook that up to the air line from the compressor. When you do this, the motor will turn so wedge the breaker bar or ratchet or whatever you use so the crank won't spin. I did this on my Silverado and had air into the crankcase and through my intake. Good luck!
Thread Starter
Launching!
Joined: Dec 2005
Posts: 232
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From: nj, edison
A small 5 gal compressor will work and you dont have to buy a gauge either. Set the piston at TDC and perform a leakdown. The compressor should have a regulator, just set it around 40 psi at first then start moving it up until you start hearing a leak. Since you have the compression tester, just remove the schrader valve from the end of the hose and hook that up to the air line from the compressor. When you do this, the motor will turn so wedge the breaker bar or ratchet or whatever you use so the crank won't spin. I did this on my Silverado and had air into the crankcase and through my intake. Good luck!
thanks for the info!.
Launching!
Joined: Jun 2009
Posts: 268
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Leak down on a race engine is somewhere around 2-5% On a street motor if its 12% the motor is acceptable. Over 15% the motor is starting to get tired. You will nead an air supply of over 100 lbs at all times to get a proper reading. You can use one of those pancake jobs because they provide adequate cfm and run over 125 lbs. All cylinders should be fairly equal on a leak down. You cant listen to a leak down and determin if something is wrong. Unless its drastic.