View Full Version : Manifold Plug Question

09-25-2012, 12:11 PM
Good day everybody,

Can anybody tell me what size allen wrench needed to use on manifold plugs on the LT1? also is there a picture of where the tranny cooler drain plug is that is mentioned to check for debris when winterizing? Thanks in advance, I've done a search but must not be looking in the right place.

Thanks again,

09-25-2012, 01:28 PM
I use a half inch drive socket wrench with no socket on it. Fits perfect.

09-25-2012, 01:30 PM
My tranny cooler doesn't have a drain plug. If you remove the inlet hose there is a screen in there. Just dig out the weeds and away you go.

09-25-2012, 01:50 PM
My plug looks like it takes a allen wrench, it's not square? I was not sure about the tranny cooler plug, I have seen some post that mention draining it for the winter. I will remove the inlet hose as you mentioned and check the screen.

Thanks ricford,

09-25-2012, 01:51 PM
I also leave that inlet hose off in the winter.

09-25-2012, 04:27 PM
I will do that too. I ran into another post that talked about the allen wrench I think I need for the manifold plugs, I believe they said it was a 9/16, I will try it out and see if it works.
Thanks again for your help,

09-26-2012, 09:20 AM
Tranny cooler plug on engine side...3/8 box wrench should do it...at least that size on my '95 FWIW..I store in my garage and run TV anti-freeze threw system...supposedly has some corrosion protection. Then drain and put away...dry block...

Miss Rita
09-26-2012, 01:11 PM
The OEM manifold plugs on my '89 required a 9/16" allen wrench; good luck on finding one of those, I couldn't find one at the usual outlets. I imagine that some heavy equipment parts place may stock them.

To remove the plugs I used a bolt with a 9/16" head and locked two nuts together on the other end for traction. Once the allen head plugs were out I replaced them with brass plugs that can be removed with a 1-1/16" wrench.

09-26-2012, 01:20 PM
I replaced the hex drive manifold drain plugs with 3/4 NPT brass plugs, uses 5/8" wrench (as I recall) now to remove. Much better than the strip-prone hex arrangement.

$5 x 2 from any hardware store. If they start to wear, just replace.