Blue smoke at idle
Thread Starter
TECH Resident
Joined: Feb 2002
Posts: 843
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From: Roseville, Ca.
Blue smoke at idle Hey guys!
Looking for some ideas.
I have a newly rebuilt motor in the car. Details are in the sig.(new stock lower, refreshed stage 2 241's, V2) I have 1000 miles on it. From day one one, it smoked at idle. Oil pressure is great, it's never dropped below 40psi at hot idle amd 60 psi cruising. Over 70psi on a cold start. It smokes just a little on a cold start. It doesn't smoke cruising or at wide open throttle. It makes plenty of power, no dyno yet, but it traps over 118. It's been tuned, trims look great, no problems. It seems to smoke more after beating on it or a long cruise. Again, this is BLUE smoke.
It's NOT the pcv, I've swapped from a pcv to a breather and back. So then I pulled all of the plugs and #5 had oil on it. So I swapped the valveseals on that cylinder and locktited all of the rocker bolts. Same thing.
So next, I'm going to do a compression and leakdown. But what exactly will that tell me? If the tests are good, would that be a valveguide? If it's low, is that rings? Without the results yet, any idea what could it be? Anyone else have this experience? Any links to compression and leakdown diagnosis?
Any help would be appreciated.
Taking it back to the builder may not be an option.
Looking for some ideas.
I have a newly rebuilt motor in the car. Details are in the sig.(new stock lower, refreshed stage 2 241's, V2) I have 1000 miles on it. From day one one, it smoked at idle. Oil pressure is great, it's never dropped below 40psi at hot idle amd 60 psi cruising. Over 70psi on a cold start. It smokes just a little on a cold start. It doesn't smoke cruising or at wide open throttle. It makes plenty of power, no dyno yet, but it traps over 118. It's been tuned, trims look great, no problems. It seems to smoke more after beating on it or a long cruise. Again, this is BLUE smoke.
It's NOT the pcv, I've swapped from a pcv to a breather and back. So then I pulled all of the plugs and #5 had oil on it. So I swapped the valveseals on that cylinder and locktited all of the rocker bolts. Same thing.
So next, I'm going to do a compression and leakdown. But what exactly will that tell me? If the tests are good, would that be a valveguide? If it's low, is that rings? Without the results yet, any idea what could it be? Anyone else have this experience? Any links to compression and leakdown diagnosis?
Any help would be appreciated.
Taking it back to the builder may not be an option.
Last edited by Steve Gunn; Jun 8, 2009 at 07:42 AM.
If the leakdown test goes fine, than it could be valve guides/valve guide seals.
If it doesnt go so well, the compression rings may be not broken it right or may of been a junk brand to begin with. Then your looking at pulling the motor and changing all the rings or, just live with it.
Good luck man.
If it doesnt go so well, the compression rings may be not broken it right or may of been a junk brand to begin with. Then your looking at pulling the motor and changing all the rings or, just live with it.
Good luck man.
some say sealing the rocker arm stud with teflon thread sealent, particularly the intake as it commenly pertrudes into the intake port with porting the heads.
I had Cometic gaskets that were buggers to seal. I took everyting apart again and coted them with copper gasket spray and she seems to be doing well.
Good luck.
I had Cometic gaskets that were buggers to seal. I took everyting apart again and coted them with copper gasket spray and she seems to be doing well.
Good luck.
Steve, are you sure they are the correct guide seals? A few months ago someone posted a pic of 2 different seals asking which one to use. Also, are you sure you presses them down all the way? I know on my BBC stuff, you have to use a small socket and a hammer to tap them down into place...not sure if the LS1 seals are like that or not though.
EDIT:
If the leakdown goes ok and you do end up pulling the heads, a quick way to tell if the guides are trashed it to take the spring off an intake and exhaust valve. Hold the valve in the head with 1 hand and use the other hand to try and wiggle the valve stem in any direction. If theres any movement, theres your problem.
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Thread Starter
TECH Resident
Joined: Feb 2002
Posts: 843
Likes: 0
From: Roseville, Ca.
Yes sir, the heads have to come off and the valve springs and valves need to be removed.
Steve, are you sure they are the correct guide seals? A few months ago someone posted a pic of 2 different seals asking which one to use. Also, are you sure you presses them down all the way? I know on my BBC stuff, you have to use a small socket and a hammer to tap them down into place...not sure if the LS1 seals are like that or not though.
EDIT:
If the leakdown goes ok and you do end up pulling the heads, a quick way to tell if the guides are trashed it to take the spring off an intake and exhaust valve. Hold the valve in the head with 1 hand and use the other hand to try and wiggle the valve stem in any direction. If theres any movement, theres your problem.
Steve, are you sure they are the correct guide seals? A few months ago someone posted a pic of 2 different seals asking which one to use. Also, are you sure you presses them down all the way? I know on my BBC stuff, you have to use a small socket and a hammer to tap them down into place...not sure if the LS1 seals are like that or not though.
EDIT:
If the leakdown goes ok and you do end up pulling the heads, a quick way to tell if the guides are trashed it to take the spring off an intake and exhaust valve. Hold the valve in the head with 1 hand and use the other hand to try and wiggle the valve stem in any direction. If theres any movement, theres your problem.
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