Leaking Oil Plug

[Steven A.]

The oil drain plug on my '66 300 hp smallblock has always been a slow leaker. While changing the oil over the weekend, I sensed it was getting dangerously close to becoming stripped. I tightened it as much as I thought was prudent and it seemed to hold oil upon initial inspection. I drove it the next day (it was 73 in Omaha!) and all seemed fine. However, last night I noticed a fairly large puddle of oil under the car. Its probably only a tablespoon or so, but its definitely leaking more than it did before, and is a problem.

I've read in the archieves that the way to fix this is to drop the pan and replace the "nut plate" into which the drain plug fits. Sounds like the way to go, but I'm not sure were to get the right part. Is this something I can get at the local Chevy dealer? I assume I will no longer be able to use the original drain plug. Is that correct?

Any words of wisdom are appreciated.

[Brian M.]

Re: Leaking Oil Plug

Steve, check with your local Chevy dealer for part# 3723008, this is what I used to repair mine. You may be able to re-use the drain plug.

[Steven A.]

Re: Leaking Oil Plug

Thanks, Brian. By the way, how does the nut plate attach to the pan. I assume its isn't welded.

[James W.]

Re: Leaking Oil Plug

Hello Steve,

I went through this with my '64 earlier this year. You will either need to drop the oil pan and replace the nut plate inside the oil pan OR go to NAPA and buy an oversized drain plug kit and install it. I had to go the oversized drain plug route since I was short on time before leaving for Park City back in July. They make several different sizes of oversized drain plugs, I used the one that screws into the pan and has a smaller internal plug to drain the oil. The problem is it still drips! One thing I did not ask; is your nylon washer/seal that is on the drain plug in good condition? If not, you might want to replace it and try that first. I have several GM NOS washers if you need one.

As for the replacement nut place, you can have one made and tap the hole with the same thread size and pitch and still use your original drain plug.

Are you coming to the tech session this weekend at my house?

Best Regards,

James West

[Steven A.]

Re: Leaking Oil Plug

Thanks. I'm planning to be there.

[Chuck S.]

Re: Leaking Oil Plug

Another alternative is to purchase a self threading drain plug. I have used these without any problems. It sure beats dropping the pan.

[Brian M.]

Re: Leaking Oil Plug

Before mine was repaired I did go with the oversized plug. (1 size over) I purchased a plain plug, the piggy back style as mentioned above and the rubber insert type just incase. I ended up using the plain 1x oversised with no problems. Had it out for oil changes probably 3 or 4 times without a problem.

[Joe L.]

Re: Leaking Oil Plug

Steve-----

The plate is spot welded to the oil pan.