Front oil seal leaking - The 1947 - Present Chevrolet & GMC Truck Message Board Network

468chvy · 07-16-2008, 08:07 PM

First off, awsome sight, have'nt been back here for a while, nice job, keep up the good work, anyhow, my 67 has a 468 that was rebuilt, and has always had an oil leak, I dyed the oil and cleaned up the underside, drove it and pinpointed the front seal, I replaced the seal 3 times same results, some one said the big block had a oil shield from the factory that prevented oil being blown at the seal, I don't remeber anything like that, so any ideas or help would greatly be appreciated, Thanks, Nik

70rs/ss · 07-16-2008, 09:44 PM

When you pull the balancer is there a groove cut into it? An old balancer will develope the groove from the seal wearing on it, if there is one, get a new balacer or they make a sleeve that slides over the outside of the balancer shaft to "repair" it, but the sleeve is pretty thin and will eventually get a groove in it too. As for the shield, I don't remember seeing one, are you positive it is the seal and not the oil pan gasket? One last thing, are you running a PCV, and do you see oil coming out of the breather (asking because positive crankcase pressure will force oil out and no matter how good the seals are it is going to happen), not that you didn't know that, but just an FYI for a couple other causes. Good Luck!

468chvy · 07-16-2008, 10:36 PM

I am running a new balancer, and I dyed the oil and did a check on it, the oil is coming from the seal, I followed the black light stream from the seal down the pan, I don't have a pvc, I had one on at one time but than a old truck guy said not to run 'em, the breathers do have some oil coming out of them, ????? I hate having to put cardboard on my garage floor everytime I drive it, anyone? I know chevy says that you only need 50 psi or so for sufficient oil delivery, I am running about 70 or so, after all an engine is just a big pump, right? I think it is pumping to much air in, the erson gear drive I have on it also might be the culprit, but I don't think so, Any suggestions,

**truckdude239** · 07-16-2008, 11:20 PM

installl a pvc vavle your crankcase pressures are too high

**El Jay** · 07-17-2008, 12:31 AM

70rs/ss · 07-17-2008, 11:14 AM

Yep, there is always a cettain amount of blow-by in any motor and that pressurizes the crankcase, it will push oil out of the path of least resistance. Put the PCV valve in a baffled hole in the VC and get a good source of vacuum (at the base of the carb if you can or in the air cleaner assembly) then have a breather on the other side of the motor in a baffled hole as well. The 70 PSI of oil pressure is a bit high too. Some folks use the addage of 10 PSI per thousand RPM, but that is just not true for a street driven vehicle, as too much pressure can be as bad too little, and the other issue is sucking the pan dry (too much oil on the top of the motor) as well as pushing oil out of the motor, kinda like your's. I am pretty for sure the PCV will solve it, or at least a lot of it. You may want to think about swapping the oil pump for a stock flow and pressure pump, just for lowering drag on the cam gear and to prevent any more issues from excessive oil pressure over the life of the motor, but it isn't do or die, just one man's thoughts. Good Luck!

07-16-2008, 08:07 PM	#1
468chvy Registered User Join Date: Mar 2008 Location: Menomonee Falls WI Posts: 14	Front oil seal leaking First off, awsome sight, have'nt been back here for a while, nice job, keep up the good work, anyhow, my 67 has a 468 that was rebuilt, and has always had an oil leak, I dyed the oil and cleaned up the underside, drove it and pinpointed the front seal, I replaced the seal 3 times same results, some one said the big block had a oil shield from the factory that prevented oil being blown at the seal, I don't remeber anything like that, so any ideas or help would greatly be appreciated, Thanks, Nik

07-16-2008, 09:44 PM	#2
70rs/ss Registered User Join Date: Dec 2004 Location: Northern AZ Posts: 7,271	Re: Front oil seal leaking When you pull the balancer is there a groove cut into it? An old balancer will develope the groove from the seal wearing on it, if there is one, get a new balacer or they make a sleeve that slides over the outside of the balancer shaft to "repair" it, but the sleeve is pretty thin and will eventually get a groove in it too. As for the shield, I don't remember seeing one, are you positive it is the seal and not the oil pan gasket? One last thing, are you running a PCV, and do you see oil coming out of the breather (asking because positive crankcase pressure will force oil out and no matter how good the seals are it is going to happen), not that you didn't know that, but just an FYI for a couple other causes. Good Luck!

07-16-2008, 10:36 PM	#3
468chvy Registered User Join Date: Mar 2008 Location: Menomonee Falls WI Posts: 14	Re: Front oil seal leaking I am running a new balancer, and I dyed the oil and did a check on it, the oil is coming from the seal, I followed the black light stream from the seal down the pan, I don't have a pvc, I had one on at one time but than a old truck guy said not to run 'em, the breathers do have some oil coming out of them, ????? I hate having to put cardboard on my garage floor everytime I drive it, anyone? I know chevy says that you only need 50 psi or so for sufficient oil delivery, I am running about 70 or so, after all an engine is just a big pump, right? I think it is pumping to much air in, the erson gear drive I have on it also might be the culprit, but I don't think so, Any suggestions,

07-16-2008, 11:20 PM	#4
truckdude239 Senior Member Join Date: Sep 2005 Location: Lewisville, Nc Posts: 10,237	Re: Front oil seal leaking installl a pvc vavle your crankcase pressures are too high __________________ David fuller Ase Certified Mechanic Click here to help support our board!! 1971 Chevy c-10 under going a 4.8l LSx swap Build Thread http://67-72chevytrucks.com/vboard/s...d.php?t=421305 2007 Honda Accord my daily 145kmiles 2002 Honda Accord 4 door With 330k(sisters car) 2005 toyota Avalon 228k( brothers car) 2002 Sububran 5.3 245k 2000 Tahoe 5.3l 378 General manager for Marco's Carwash & lube

07-17-2008, 12:31 AM	#5
El Jay Gone to greener pastures Join Date: May 2007 Location: Gateway to the Delta Posts: 7,354	Re: Front oil seal leaking __________________ '69 Chevy 1/2 T LWB Stepper: Daily Beater '72 GMC 3/4 T Fleet: Another Daily Beater '72 Plymouth Gran Coupe: ? "Ah women. They make the highs higher and the lows more frequent." Friedrich Nietzsche "Never kick a fresh turd on a hot day." Harry S. Truman GUN CONTROL: Never having to say, "I missed you." Always fire two warning shots into your attacker's chest area before putting a bullet between his eyes. Paraphrased from Louis Awerbuck

07-17-2008, 11:14 AM	#6
70rs/ss Registered User Join Date: Dec 2004 Location: Northern AZ Posts: 7,271	Re: Front oil seal leaking Yep, there is always a cettain amount of blow-by in any motor and that pressurizes the crankcase, it will push oil out of the path of least resistance. Put the PCV valve in a baffled hole in the VC and get a good source of vacuum (at the base of the carb if you can or in the air cleaner assembly) then have a breather on the other side of the motor in a baffled hole as well. The 70 PSI of oil pressure is a bit high too. Some folks use the addage of 10 PSI per thousand RPM, but that is just not true for a street driven vehicle, as too much pressure can be as bad too little, and the other issue is sucking the pan dry (too much oil on the top of the motor) as well as pushing oil out of the motor, kinda like your's. I am pretty for sure the PCV will solve it, or at least a lot of it. You may want to think about swapping the oil pump for a stock flow and pressure pump, just for lowering drag on the cam gear and to prevent any more issues from excessive oil pressure over the life of the motor, but it isn't do or die, just one man's thoughts. Good Luck!



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