LS1 block drains

[Terry M.]

Looks like there are two:
Large brass plug on drivers side, just above the pan rail, between the front of the case and the mount. This one takes a 17mm hex.
A smaller brass plug on the passenger side directly above the starter.

Has anyone removed the large one, and is it really a coolant drain for the case?

[Clem Z.]

Re: LS1 block drains

sounds like you found them according to the shop manual. pass side towards the rear and driver side towards the front of the block

[Terry M.]

Re: LS1 block drains

Thanks for the confirmation Clem, now to find a 17mm hex tool. It doesn't seem worth the trouble to drop the starter to drain the cylinder case.

[Christopher R.]

Re: LS1 block drains

17mm hex is a common size used on foreign cars. Believe VW and Audi use that today for oil pan drain plugs.

[Chas Kingston]

Re: LS1 block drains

Just an RCH smaller than 11/16"

Geezer

[Terry M.]

Re: LS1 block drains

I found 17mm hex drive socket at Snap-on on-line store, also 17mm stock for the drive bit -- so I do have a source if nothing more economical becomes available. The hole is not a full hex, so I want to have the proper size tool so as not to damage the brass plug.

I really was looking for some assurance that the large (about 1.5 inch diameter) brass plug on the driver's side toward the front is really a coolant drain. From the F-body FSM it looks like this is also the location for the block heater, so that may account for the large size.

[Terry M.]

Re: LS1 block drains

This large brass plug is indeed one of the LS1 cylinder case drains, and takes a 17mm hex to remove. The other is above the starter and takes a 5/16 hex according to reports. I elected not to remove the one above the starter.

Terry