Oil Sump Plug size

[archigator]

What's the oil sump plug size and thread pitch on a Sprint sump? (If I take mine off to look, all the oil will come out...) Couldn't find it in the archives...

Thanks,

Gary
'71 Sprint FHC
Miami, Florida

[garyeanderson]

I think it depends! what engine? 4 bolt or 6 bolt sump. The 2 in the photo are from a 1964 4 bolt engine (red one in the mike) and a 6 bolt from 1968. The 68 appears to be 1/2 x 20 (nyloc threaded onto it) and the early 4 bolt sump plug bolt looks like 3/4 unf but may be something BS, I did not have a nut that fit so can't say with to much certainty. There was a later sump plug too. I have that on my gated oil pan on the 711 based 1700twin cam that was built by Kenny Duclos. I use a 1/2 box to pull the sump plug, I don't know what the thread is. So there you have it. the best way is to measure your's the next time you change the oil.

Gary

[types26/36]

As Gary says I think your Sprint will be 1/2" UNF.
I picked this chart up off the net a while ago.

[Galwaylotus]

I use a 1/2 box to pull the sump plug, I don't know what the thread is.

Standard for 1/2" hex is 5/16" thread.

[garyeanderson]

I use a 1/2 box to pull the sump plug, I don't know what the thread is.

Standard for 1/2" hex is 5/16" thread.

I had a look to see and after trying the 1/2, it didn't fit so the next one up was a bit sloppy. I don't know what it is but the 9/16 seems to work. I'll measure it when I change the oil next time.

Gary

[Galwaylotus]

Could it be a 13mm hex? If a newish sump pan was used, I believe the US auto industry is now using metric fasteners.

[CBUEB1771]

Just ran down to the basement to check, the thread is 1/2"-20 and the hex is 7/8" across the flats. This is for my +2S and so should be the same for a Sprint, both being six-bolt lip-seal crank engines. Gary appears to have an aftermarket sump plug. The originals have no forging marks on the head, rather you can see lathe marks as these appear to be turned from 7/8" hex bar stock.

[vernon.taylor]

Salut

That's useful to know - I asked the same question a while back when I thought about buying one of these:

http://www.quickvalve.co.uk/f101.htm

@+

Vernon

[Chancer]

I use a 1/2 box to pull the sump plug, I don't know what the thread is.

Standard for 1/2" hex is 5/16" thread.

That is true for a bolt or setscrew but a sump plug is neither of these, it has a larger sealing flange than the thread diameter and the hexagon is often deliberately reduced in size to prevent overtightening, people seeing a 15/16" hexagon may well in ignorance torque it up like a bolt of that size.