Freeze Plug diameter

[TexasTruck72]

I noticed when changing the starter on my 360 FE yesterday that the freeze plug directly above the starter is on its last legs (sweating, etc). Does anyone know the diameter/size of this freeze plug location? I couldn't get a set of calipers up in there easily. I didn't want to scrap away the rust/corrosion for fear of it getting worse, or at least until I'm ready to replace it. I've replaced 2 of the freeze plugs on this engine already and they were 1.75" diameter (the largest ones). This freeze plug in question looked to be slightly smaller if not close in size. Any help would be appreciated. Thank you.

[basketcase0302]

Sorry I can't help you with the exact measurement but remembering this from years past, (ask me about carving out a hole in the firewall of a dodge to replace a free plug)!

You could always source a "kit" locally that should have the entire set needed for the engine similar to this one:

https://www.summitracing.com/parts/mel- ... /make/ford

[TexasTruck72]

Thanks. I think I found out that all 6 large freeze plugs for the FE block are the same diameter from looking at the kits you can purchase. That would mean all 6 of the large ones are 1.75" diameter and can be had for about a $1.50 each at your local NAPA auto parts. I bought a few because I've replaced them before only to have one get out of round and not seal properly. I only asked here in case someone had a 360/390 out of the truck and could measure more easily.

[basketcase0302]

Jack,
If no one else responds maybe even try to find an old skool local machine shop to verify.
Can't reach the bore with an inside caliper?

[CH3NO2]

I believe they are 1" 49/64th of an inch.

[zgerbic]

I just built a 390 last week and saw this post.

The plugs are stamped 1 3/4", which means they are for a 1 3/4" inch hole. I believe the hole is 1 3/4 (1.75") in diameter from the factory. The hole may end up slightly larger due to sanding, scraping or honing over time due to rust. The actual size of the copper plugs you would install are 1 49/64" (1.765"). When you install them, under some force, they will seat into the ~1.75" hole since they are only .015" larger than the hole and have some side wall pressure/flex to keep from popping out. A 1 3/4" actual size plug would easily pop out of a 1 3/4" hole with just a little pressure, or just fall out.

This is why they are sometimes listed as 1 3/4" plug or 1 49/64" plug but are actually the same size. Hope this eliminates any confusion about why you will get two answers to this question.