1956322 Posted August 20, 2017 Share Posted August 20, 2017 Does anyone know where to find a non oversize oil pan drain plug for a 322.. All I'm finding are the self tapping oversize ones Link to comment Share on other sites More sharing options...
Beemon Posted August 20, 2017 Share Posted August 20, 2017 AutoZone or O'Reilly. Any 18mm drain plug should fit. Link to comment Share on other sites More sharing options...
1956322 Posted August 20, 2017 Author Share Posted August 20, 2017 So the book says 18mm which the few I find have a 19mm hex.. Online they are saying 11/16-20 with a one inch hex... My current one has a one inch hex.. Hmm... The 18mm ones I'm seeing do look to small Link to comment Share on other sites More sharing options...
Barney Eaton Posted August 20, 2017 Share Posted August 20, 2017 Why did Buick use a mm threaded drain plug in the '50's? I would have thought the threads would be 1/2 or 3/4 standard threads. Link to comment Share on other sites More sharing options...
1956322 Posted August 20, 2017 Author Share Posted August 20, 2017 No idea but the book does say that both the engine and transmission drain plugs are 18mm.. Now 18 by what it doesn't say lol Link to comment Share on other sites More sharing options...
60FlatTop Posted August 20, 2017 Share Posted August 20, 2017 Wow! I had a flashback to the 1980's. I have forgotten about my nailhead oil plug experience. For some reason I bought a self tapping plug. It takes a little extra torque to put those in. That was when I discovered the plug threads into a steel plate tack welded inside the sheet metal pan. The tack weld broke. Then I had a free spinning partly installed self tapper and a loose plate on the inside. I had to drop the pan and weld the plate back in. Dropping the pan on those cars is very close to the same amount of work as removing the engine. I still remember sneaking those four pan bolts about the crossmember in. I used a 1/4" drive, extension, and a universal joint. Now I'm trying to remember what is in there now. I'll have to check. Be careful. Bernie 2 Link to comment Share on other sites More sharing options...
Bhigdog Posted August 20, 2017 Share Posted August 20, 2017 50 minutes ago, Barney Eaton said: Why did Buick use a mm threaded drain plug in the '50's? I thought the same thing but the plug in my spare oil pan measures .708" which is 18MM. So, no answer as to why but they did.................... Bob 1 Link to comment Share on other sites More sharing options...
old-tank Posted August 20, 2017 Share Posted August 20, 2017 52 minutes ago, Barney Eaton said: Why did Buick use a mm threaded drain plug in the '50's? I would have thought the threads would be 1/2 or 3/4 standard threads. ...and the spark plugs are 14 mm ...and wheel rim size everywhere is in inches... 1 Link to comment Share on other sites More sharing options...
NTX5467 Posted August 20, 2017 Share Posted August 20, 2017 A "plate" tack-welded to the inside of the oil pan for the oil pan drain plug? Just curious. In the later 1990s, I was looking through the GM parts database, Buick 3800 to be specific, and I noticed a ref number for a part I hadn't seen listed separately before, an engine oil pan drain plug "bung". It was only listed for a few model years, being a part of the oil pan unit in other years . . . I looked. So, I ordered one to see what it was. When we look through the hole with the oil pan drain plug removed, we see "threads" and the oily blackness of the void inside of the oil pan. What I was surprised at was that there were ONLY THREE THREADS in that "nut" that was to be attached to the inside of the oil pan. THREE thin threads! No wonder some got stripped out! By this time, GM engine drain plugs were standardized in size and configuration. In more recent years, some GM applications used a softer-material drain plug that was a golden-brown color and CAST rather than machined. Those particular drain plugs were notorious for wearing and stripping out. Only about a $1.00 or so. When the oil change techs started to ask for a new one (due to wear of the threads), I'd look to see if WE had done the last oil change or prior ones. If so, I charged the plug to the shop so there wasn't a conversation between the customer and the service advisor about the oil pan drain plug needing to be replaced (which used to NEVER happen!), so better to just charge it to the shop and go on. I was the only one who saw the reasoning behind that, it seems, but I never got questioned on it. My later associates just charged it to the customer. The drain plug on my Camaro became "weak", so I went in search of ways to get around that, knowing about the three threads issue. At Pep Boys, I found a whole end cap side display of drain plugs! Including a chrome-like "standard" engine oil drain plug w/gasket. I first learned of the oversize plugs soon after I went to work at the dealership. There were different "oversize" sizes. Single, double, and triple oversize, with a different "gasket" for them. Pure aftermarket. At that time, these were to save the oil drain plug nut/bung threads by cutting deeper ones. The related gaskets seemed to be more porous than the hard nylon ones the factory used back then. Engine oil drain plug gaskets? Several evolutions there, too! What was the spec engine oil drain plug gasket for Nailheads in the 1950s? Just curious. NTX5467 Link to comment Share on other sites More sharing options...
1956322 Posted August 20, 2017 Author Share Posted August 20, 2017 I'm guessing a copper crush washer 1 Link to comment Share on other sites More sharing options...
1953mack Posted August 20, 2017 Share Posted August 20, 2017 The Part Books say a 3/32"-thick fibre for both engine and transmission drain plug gaskets. 1 Link to comment Share on other sites More sharing options...
Bhigdog Posted August 20, 2017 Share Posted August 20, 2017 The washer on my spare "original" pan appears to be some sort of fibre. I've seen them made from copper, fibre, and plastic of some sort. I've made a couple from nylon and that seemed to work fine. They're under no pressure so I'm guessing one cut from a cereal box would work in pinch..................Bob 3 Link to comment Share on other sites More sharing options...
Beemon Posted August 20, 2017 Share Posted August 20, 2017 5 hours ago, 1956322 said: So the book says 18mm which the few I find have a 19mm hex.. Online they are saying 11/16-20 with a one inch hex... My current one has a one inch hex.. Hmm... The 18mm ones I'm seeing do look to small My original engine has the 1 inch hex, my new engine has the parts counter plug. The parts counter plug does have a smaller head, but works. 1 Link to comment Share on other sites More sharing options...
1956322 Posted August 20, 2017 Author Share Posted August 20, 2017 So you just used the 18-1.5 plug with I think a 19mm hex and no problems thread wise Link to comment Share on other sites More sharing options...
Beemon Posted August 20, 2017 Share Posted August 20, 2017 I am to assume my oil pan wasn't tapped, so you should have no issues. What's wrong with the original plug anyways? Link to comment Share on other sites More sharing options...
1956322 Posted August 20, 2017 Author Share Posted August 20, 2017 The hex head has seen better days.. It's fine has been for years but I'd like to replace it at some point Link to comment Share on other sites More sharing options...
Frank DuVal Posted August 25, 2017 Share Posted August 25, 2017 On 8/20/2017 at 10:29 AM, old-tank said: ..and wheel rim size everywhere is in inches... Except for those short lived metric rim sized Michelin TRX tires back in the late 70, mid 80s. I found them on Mustangs and Peugeot 505s. Coker tire makes them now. Link to comment Share on other sites More sharing options...
1956322 Posted March 20, 2018 Author Share Posted March 20, 2018 Just in case anyone finds this thread..I just did an oil change and used the 18mmx1.5 thread plug with a 19mm hex.. Fits perfect 1 1 Link to comment Share on other sites More sharing options...
Beemon Posted March 21, 2018 Share Posted March 21, 2018 19mm hex... must be close to 3/4" since I just did an oil change on Saturday, too. Glad it worked out for you. Link to comment Share on other sites More sharing options...
1956322 Posted March 21, 2018 Author Share Posted March 21, 2018 Yes 3/4 is technically 19.05 mm I believe lol Link to comment Share on other sites More sharing options...
NTX5467 Posted March 22, 2018 Share Posted March 22, 2018 All you're finding is the "oversize" plugs as they figured that IF there were any of those oil pans still in use, they'd need that oversized drain plug (wear on the three threads of the "bung" inside the oil pan). OF course, all that "bung" is is a large nut with the correct threads tack-welded to the inside of the oil pan. It CAN be replaced, if needed. NTX5467 1 Link to comment Share on other sites More sharing options...
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