When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
Happy Memorial Day, especially to those that have served!
I am looking for a little direction and advice. I changed out a leaking rear main seal on my 1966 L79 327. The rear main seal came out and the new one went in really nicely. While I was at it, I stripped and painted the oil pan. The railings of the oil pan looked really good and straight. I cleaned off the old cork and rubber 4 piece gasket and replaced it with a one-piece Fel-pro blue gasket. The engine is still in the car. After installing and torquing the oil pan, using new bolts supplied by Fel-Pro, I didn't notice any leaking, so I took it out for a short test drive. I came back to find all over the passenger side of the engine. I put the car back up on the lift and checked the tightness of the oil pan bolts, and all of them were loose, even though I torqued them to 8 ft lbs for the 1/4" bolts and 18 ft lbs for the corner bolts. I was having some issues with my torque wrench, but they shouldn't have been that loose. I tightened all the bolts up again and started the engine. I couldn't see much at idle, but I revved the engine to 2000 rpm or so for a bit, and then I could see oil dripping again. First I thought it was coming from right at the bottom of the front of the oil pan, but it appears to be pooling there, and looking closely, at idle now, I could see oil spitting out between the gasket and oil pan right below the front pan bolt in the picture, just maybe 1/2 or 3/4" down from the flat surface of the front of the block. I did put a dab of Ultra Black RTV in each corner as suggested by Fel-pro, and if you zoom in, you can see it slightly pushed out in the corner. Fel-pro didn't say to use RTV in any other places, so I didn't.
So now, what are my options? What can I do to fix this? I didn't notice a leak in this area before. I assume I have to pull the pan off again, but what do I do? Do I have to buy another gasket? Should I be putting RTV on the gasket or on the oil pan? If so, which sides? I went with the blue Fel-pro one-piece gasket as everyone seems to claim they are superior and don't leak. No to with me obviously. Suggestions?
There's 2 different styles of the 1piece gasket...each one is different based on what/which timing chain cover you have..
EDIT:
Especially... take note, if the timing chain cover has been replaced..
AI Overview
For a C2 Corvette Small Block Chevy, use the Fel-Pro OS 34509 T for a thin front seal (1957–1974) or the OS 34510 T for a thick front seal (1975–1985). According to CorvetteForum discussions, these 1-piece, molded rubber-over-steel-core gaskets are much better than old 4-piece gaskets, but they must be installed strictly dry except for RTV silicone in the four block corners.
1. Is this the correct gasket for your engine?? These pan gaskets came in two different part numbers depending on the diameter/radius of the pan curved opening. The original oil pan took one size gasket ........and later replacement pans required another size So verify your part numbers. Measure the oil pan opening if needed to verify dimension. If I remember correctly, a very small amount of silicone sealant was required in a couple of spots to ensure correct sealing. But don't overdo the silicone sealant.
2. Is your PCV working correctly and not building pressure inside the engine?? Check if cover on oil fill tube( just over the PCV) to make sure it is not broken or cracked. If so, air will come in and go straight into PCV, leaving engine not ventilated and under slight pressure.
Two things:
2. Is your PCV working correctly and not building pressure inside the engine?? Check if cover on oil fill tube( just over the PCV) to make sure it is not broken or cracked. If so, air will come in and go straight into PCV, leaving engine not ventilated and under slight pressure.
Larry
I could see oil spitting out between the gasket and oil pan right below the front pan bolt
This certainly sounds like the crankcase is pressurized.
Here is another picture of the oil pan, taken further out, the metal piece is pointing where I see the oil spitting out. I measured the oil pan and purchased the shorter, or thinner Fel-pro. I don't know that the oil pan has been replaced, it sure looked like the pan gasket and rear main seal had been there awhile. Number's matching engine, supposed to be 52,000 miles. When I set the gasket on the oil pan before I put it up to the engine, it looked correct, there seems to be a big difference between the two parts.
Some previous owner had removed the PCV system before my purchase, there was just a line running from the oil filler tube over the air conditioner condenser and down to the frame. I purchased the correct PCV valve, screwed it into the filler tube, and ran a new rubber hose to the vacuum port on the back of the carburetor. I had to find an original vent tube for a 350 hp engine and mounted it in the back of the block, and have the correct hook-up to the air cleaner. So, the PCV system should be working, I took it back to stock, but I am just assuming that. I can take off the PCV valve and shake it to make sure it is working. The oil cap seems fine, but I will check that too. Just don't understand the leak, it didn't leak before I changed the rear main seal and pan gasket. So if I am building up crankcase pressure, how do I check that (other than the above) or how do I correct?
Hoping you don't have the same problem I did with the rubber gasket. It was suppose to be a Fel-Pro gasket, and although it did come in a Fel-Pro box, the box had been opened. The rubber gasket was a poor fit and lacked the hard spacers in the bolt holes. I had leaks at the timing cover and finally dropped it to find the seal around the front of the pan had split in the center and was hanging out the front of the pan.
I went back to cork and have no leaks, not that I think rubber is a bad idea.
Ron
The second picture doesn't help either. Did you compare the new gasket like this video? I don't know if you have the right gasket or not, but I recently replaced one and there was no issue. This may or may not help, but it doesn't cost anything to watch.
The gasket I was shipped was the 34509 T Fel-Pro one piece, suggested because this is a numbers matching 66 L79. It is leaking in the front between the pan and the timing cover. I did not measure the pan when I took it off, as I ordered the gasket and had it for a few weeks before I took the pan off to replace the rear main seal and I wanted to make sure I had it on hand. Could the oil pan have been changed? I don't know.
The old gasket was a 4 piece cork and rubber. It wasn't leaking that I could tell, other than the rear main. It certainly wasn't spitting oil out. I just went out and measured the old rubber front seal. It came out as 13/32's deep with the calipers. I didn't squish it, so it could be 12/32's, or 3/8". It was about 7/16" wide. Could this tell me that I need a "thick" gasket, the 34510, instead of the 34509 which is the "thin" gasket?
If I am going to try this again, maybe I am just going to have to order both gaskets to have them here and then do the measurements and fit tests when I pull the oil pan off again.
Here are some past threads and information on measuring the pan for the correct seal if you have the pan off.
The original front seal for up to a 75 SBC is only 1/4" thick. As you can see, the front seal for a 75 and later SBC must be 1/8" thicker (~3/8" thick) to seal.
So, with my old rubber front timing chain/oil pan seal being 3/8" thick, it would seem that a previous owner probably replaced the oil pan with a service replacement pan with the thicker gasket. The oil pan certainly seems to be a Corvette part, with the design and the location of the oil drain plug. Regardless, I guess I am going to order another Fel Pro one piece gasket, the OS 34510 T thick gasket, and give it another try. I noticed that the thick gasket has cut-outs for oil dipsticks on both sides, versus only the driver's side on the thin gasket. Do you just install the gasket and let the passenger side dipstick cut-out stick out the side of the gasket? As long as it doesn't leak, I guess that the only issue would be that you have a little blue tab sticking out from the pan.
So, with my old rubber front timing chain/oil pan seal being 3/8" thick, it would seem that a previous owner probably replaced the oil pan with a service replacement pan with the thicker gasket. The oil pan certainly seems to be a Corvette part, with the design and the location of the oil drain plug. Regardless, I guess I am going to order another Fel Pro one piece gasket, the OS 34510 T thick gasket, and give it another try. I noticed that the thick gasket has cut-outs for oil dipsticks on both sides, versus only the driver's side on the thin gasket. Do you just install the gasket and let the passenger side dipstick cut-out stick out the side of the gasket? As long as it doesn't leak, I guess that the only issue would be that you have a little blue tab sticking out from the pan.
So just an update. I removed the oil pan again and measured it. It does appear that some previous owner had changed out the oil pan with a service replacement pan, requiring the thick front seal. The new gasket should be here tonight and I will get it mounted in the next day or two and give an update on, hopefully, the lack of leaks. Thanks for all the assistance.
Yes, two different ones out there by felpro. I do not know which one you got but the way to do it is to get some RTV preferably blue color. Then clean the spot with brake cleaner or something like that then apply a small amount using your fingers to spread into the cracks. Let it dry overnight. First check that the bolts are torqued down.
Oil Pan Gasket Leak, Oil Spitting Out
