Engine: Oil drain plug threads

[wdills]

Is the Stude V8 oil drain plug 5/8-18 thread? I want to get a magnetic plug and want to buy the right size.

[Alan]

Crazy thing is I have seen 2 different threads on Studes. for the drain plug. One is straight thread 5/8" X 18 and the other 3/8" taper pipe.

[Mike]

Crazy thing is I have seen 2 different threads on Studes. for the drain plug. One is straight thread 5/8" X 18 and the other 3/8" taper pipe.

Alan's seen a lot more Stude oil pans than I have. What were the tapered plugs on?
The few I've seen had straight threads, probably 5/8" x 18. The plugs screwed into a nut plate, spot welded inside the pan. The plate wasn't sealed to the skin of the pan, and of course the straight threads weren't intended to seal either. The plug had a flange and gasket that sealed against the skin of the oil pan. If the flange was square with the threaded portion of the plug, ( some weren't ), and the skin was flat around the drain hole, it worked fine.
If you replace the plug, make sure you get one with the flange and gasket.
Mike M

[Jeffry Cassel]

Older cars had a different plug than later models. be sure you have the correct one for your car!

[r1lark]

Magnetic oil drain plugs were available on the Stude trucks, so you may be able to get one from our Studebaker parts vendors. (Trying to make more points with StudeRich !)

[thunderations]

I remember as a teen, a hundred years ago, working at a Standard Oil Station in Mishawaka, IN that many cars had stripped drain plugs and the fix was an oversize, tapered, self tapping plug. I think this was common practice, so the plug you have may not be the plug it was born with. My guess is that if it's a straight thread, it may be original and if it's tapered, it might be a replacement plug.

[Robert Crandall]

I had that problem when I bought an off topic 1957 car. The oil plug was an NTP plug held in with ten wraps of Teflon tape because the previous owner could find nothing to fit. I could not match the thread with my thread gages, so I kept using that and lots of Teflon tape. When I bought the repair manual I discovered the threads are 15mm. It was easy to find a 15mm replacement plug at the FLAPS, and it fit easily. That may not be the case here, but the manual for your car may give the thread size.

[Corley]

I remember as a teen, a hundred years ago, working at a Standard Oil Station in Mishawaka, IN that many cars had stripped drain plugs and the fix was an oversize, tapered, self tapping plug. I think this was common practice, so the plug you have may not be the plug it was born with. My guess is that if it's a straight thread, it may be original and if it's tapered, it might be a replacement plug.

When using one of these oversized self tapping plugs, be sure to flush the chips out of the pan after you once install the self tapping plug. That is, install it, then remove it, gather everything you can with a magnet sticking in the hole, then flush by dumping a quart or two of oil through the engine and out that hole. Next, check the self tapping plug itself, as they have slits that hold chips material. Clean everything thoroughly! It MAY still not get all the chips out, so try to avoid these replacements if possible. Sometimes there is just no other good way available to repair a stripped out drain plug hole though.

[RadioRoy]

I just get a very strong button style magnet and attach it to the inside end of the existing drain lug with epoxy. Works great and is satisfying to remove metal filings when changing the oil.

I'm not thrilled that the filings are there, but happy that my magnet caught them.

[thunderations]

Maybe the engine is doing a "self re-bore" and you will gain a few cubic inches and some horse power.

I just get a very strong button style magnet and attach it to the inside end of the existing drain lug with epoxy. Works great and is satisfying to remove metal filings when changing the oil.

I'm not thrilled that the filings are there, but happy that my magnet caught them.

[Skip Lackie]

I remember as a teen, a hundred years ago, working at a Standard Oil Station in Mishawaka, IN that many cars had stripped drain plugs and the fix was an oversize, tapered, self tapping plug. I think this was common practice, so the plug you have may not be the plug it was born with. My guess is that if it's a straight thread, it may be original and if it's tapered, it might be a replacement plug.

Yes. Back around 1966 when I lived in an apartment and couldn't change my own oil, a gas station bozo did that to my 62 Chevy's 327, and it has dripped ever since. Have changed the oil myself since then, but have never found a gasket that will seal it completely.

[TWChamp]

I've done the same as Roy on several of my drain plugs. I also do it for the tranny and rear end plugs.

[gordr]

Not to mention, that on most engines, the oil pan drain is not at the lowest possible point on the pan. Certainly not on most Studebakers. Which means you can let it drip until the cows come home, and sludge will remain in the pan. Of course, putting the plug in the absolute bottom of the pan makes it very vulnerable to damage from road debris, etc. What to do, what to do?

[Dwain G.]

When I first went to work for the Navy, we had a drawer-full of those self tappers for the Dodge pickups. I found that the threads in the pan were okay. It was just the drain plugs that were getting stripped out.

[bensherb]

When I got my 62 GT the drain plug leaked, I figured the gasket on it was bad. When I changed the oil I found that the drain plug fit extremely loosely. It was 5/8-18 but the pan had different threads, it was larger. I don't remember exactly but I think about .030 larger in diameter, don't remember what the pitch was. I made a new plug to match the threads on the pan and oringed it, no more leaking!