jetblast

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.

SweetS10V8

iTrader: (4)

You need to do a leak down test, not a compression test. That will tell you if you have rings failing.

jetblast

i thought that was next. i got get a compressor and the guage.
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.

jetblast

how big of a compressor is necessary to do the ck accurately?

conan

iTrader: (5)

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.

SweetS10V8

iTrader: (4)

jetblast

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.

racer7088

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.

jetblast

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.

jetblast

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?

racer7088

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.

jetblast

you must be Erik ... the timing and fuel definitely have made a noticeable difference. for example: i had one track event that i kept leaning it out to the point of kr, the dipstick blew out further than ever, backed it off . i was running 18* on the 100w.
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.

BlownChevySS

iTrader: (1)

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!

SOMbitch

iTrader: (8)

Putting a piece of hose over the dipstick tube will help you listen to the crankcase and don't be concerned if the leakage is as high as 15%-17%.

jetblast

thanks for the info. too late though. i made a simple leak ck. gauge for 30$, and got a small 4 gal. compressor. i am using the compression hose like you said. i hope my 3 ft long torque wrench is good enough to hold it still.

hell, i'll be happy if they have similar leakage... if it's 25% what i'm to do?
thanks for the info!.

SweetS10V8

iTrader: (4)

Fix where its leaking.

BlownChevySS

iTrader: (1)

A leak is a leak and will probably only get worse so even if its 5% you should still fix the problem even if it means you got tear apart the motor

jetblast

i'll be doing the leak ck. this wk... see you then!

SweetS10V8

iTrader: (4)

10% is completley acceptable..Your looking for one that leaks dramatically more than the others.

tom falco

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.