Burning oil on decel after rebuild
10-05-2005, 09:48 AM
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Burning oil on decel after rebuild I'm about ready to push it off a cliff. Shortblock rebuilt locally, honed, new rings and bearings you name it. Cylinders measured for round and spec'd with pistons.
Heads were machined, valves reground, new valve seals. (stock 241 heads).
Did the LS6 valley cover PCV and running a AMW catch can. I'm at the end of my rope. The only thing I didn't do was have the injectors rebuilt. The motor has 600 miles on it. It burns oil the exact same ways as before the rebuild, let off at higher rpms and get back on the gas and blue smoke pours out.
I've disconnected the PVC to see if it's feeding oil into the intake, no change. I've tried open venting where the oil cap is, no change. My catch can did have a small pool of oil in it. And where the intake meets the heads there is a coating of oil. Dipstick shows oil level going down drastically. New LS6 oil pump and pick were used, oil pressure is normal 30psi idle 60 psi above 3000 rpms. I would think it's obviously a vacume issue since of the high vac at higher rpms and it can't bleed it off. Any suggestions?
Heads were machined, valves reground, new valve seals. (stock 241 heads).
Did the LS6 valley cover PCV and running a AMW catch can. I'm at the end of my rope. The only thing I didn't do was have the injectors rebuilt. The motor has 600 miles on it. It burns oil the exact same ways as before the rebuild, let off at higher rpms and get back on the gas and blue smoke pours out.
I've disconnected the PVC to see if it's feeding oil into the intake, no change. I've tried open venting where the oil cap is, no change. My catch can did have a small pool of oil in it. And where the intake meets the heads there is a coating of oil. Dipstick shows oil level going down drastically. New LS6 oil pump and pick were used, oil pressure is normal 30psi idle 60 psi above 3000 rpms. I would think it's obviously a vacume issue since of the high vac at higher rpms and it can't bleed it off. Any suggestions?
10-05-2005, 10:27 AM
#2
sounds like it could be vavle seals. does it smoke at all on start up after its been sittin a while? that would indicate that the vavle guide seals are not working so good. they can be messed up during an install and not seated properly. also do a compression leak down check. but seems as though it only does it under large amounts of vacume like at high rpm and let off gas there is huge amounts of vacume there and then you open the throttle blade back up and then you get it all that oil burning. since you have ruled out that it is not pcv valve i would check these other things.
10-05-2005, 10:49 AM
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Originally Posted by SUTTERERMAN85
sounds like it could be vavle seals. does it smoke at all on start up after its been sittin a while? that would indicate that the vavle guide seals are not working so good. they can be messed up during an install and not seated properly. also do a compression leak down check. but seems as though it only does it under large amounts of vacume like at high rpm and let off gas there is huge amounts of vacume there and then you open the throttle blade back up and then you get it all that oil burning. since you have ruled out that it is not pcv valve i would check these other things.
10-05-2005, 07:22 PM
#5
acutally how long did you run it with out the pcv valve un hooked? try running it for a couple of days. maybe there was some left in there and it just burned it when you un hooked it for a short time. that is really the only way oil can get into the intake. you say that where the intake bolts up to the heads tells me that there is quite a bit sitting ontop of there. so just try it for a while i guess. i cant hurt to try
10-05-2005, 07:33 PM
#6
Originally Posted by SUTTERERMAN85
acutally how long did you run it with out the pcv valve un hooked? try running it for a couple of days. maybe there was some left in there and it just burned it when you un hooked it for a short time. that is really the only way oil can get into the intake. you say that where the intake bolts up to the heads tells me that there is quite a bit sitting ontop of there. so just try it for a while i guess. i cant hurt to try
10-05-2005, 07:56 PM
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Burning oil like that is almost always intake related - meaning it's not coming from the compression side - like rings - it's coming from the valve seals, leak through the rocker studs, PCV system, etc. If you've disconnected the PCV the it's coming from the heads, and the only way you're going to solve it is to remove them and have them thoroughly checked by the best shop available or replace them.
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10-06-2005, 08:36 AM
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Originally Posted by 2002nhraformula
im willing to gamble on a screwed up oil ring or posibily installed wrong wring stack
george
george
10-06-2005, 08:47 AM
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I used the Federal Mogul Speed Pro rings, standard tension set. There's usually a dot on the oil ring for facing up and my enginge builder says he definately got that right. When you say screwed up ring stack I assume you mean mixing the two compression rings up.
10-17-2005, 10:29 AM
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Okay, I did a full leakdown on all of them, plus popped the intake manifold off to wipe it down.
All but two cyl's came back with 0% leakdown. The other 2 had 7% and the other had 5% so nothing horrible. The plugs were all very white, which I've read is caused by either lean or too much fuel.
The intake ports were covered in black crap, could have been running rich, but it was all over the intake manifold and entire port, I'm assuming if it was too much fuel it wouldn't cover inside the manifold. I wiped it all down, and have the pcv not connected to the intake manifold. I still have the ls6 pcv tube venting to the catch can, but since there's no vacume I doubt it's doing anything.
I also pulled a few rockers off and verifyed that the rocker bolts to go into the intake.
Any other ideas?
All but two cyl's came back with 0% leakdown. The other 2 had 7% and the other had 5% so nothing horrible. The plugs were all very white, which I've read is caused by either lean or too much fuel.
The intake ports were covered in black crap, could have been running rich, but it was all over the intake manifold and entire port, I'm assuming if it was too much fuel it wouldn't cover inside the manifold. I wiped it all down, and have the pcv not connected to the intake manifold. I still have the ls6 pcv tube venting to the catch can, but since there's no vacume I doubt it's doing anything.
I also pulled a few rockers off and verifyed that the rocker bolts to go into the intake.
Any other ideas?
fixes it every time 