Oil Drain plug from Hell

[jeremywatco]

Getting ready to throw my new ATK 302 crate back into the bronco.... original 302 came with a wonderful expanding drain plug for an oil plug. Since I needed to reuse the pan on my crate 302 I decided to tap new threads and do it right... or so i thought. The hole i was presented with was larger than 1/2" so I tapped an M14 hole. New plug threaded in like butter. Great right? Filled pan with oil and it promptly starts leaving out of the drain plug.... closer inspection reveals why the expanding drain plug. The drain plug hole doesnt sit straight. So when you thread in the plug it doesnt have a flat mating surface. The crush gasket makes contact on the top first and then there is probably like a 1mm gap at the bottom. For now I doused the threads in thread sealer and put it in so I could prime the oil system and such. Trying to find best path forward. Anyone seen like a super thick oring that could possibly be used to fill that gap? I guess I could take pan to a machine shop and see if a larger plug could be drilled in straight.

 

[.94 OR]

I had a leaky plug once. I had the pan out doing a rear main seal so I cleaned the pan up good and had a 1/2" fine threaded nut brazed to the outside of the pan over the existing hole. Now I can run a fine threaded bolt with a nylon gasket and they mate up flush and tight. I can put a pretty good squeeze on the bolt now without worry that it will strip out.

 

[abrogate932]

I ran into a similar problem and ended up getting a replacement 302 pan from Tom's. The pans are not identical though. The dipstick is on the opposite side and the one they send does NOT work with stock manifolds, nor does it work with Tom's aftermarket OEM replica manifolds. They don't tell you this when you order the pan kit, they leave you to figure out that the dipstick just doesn't work period. You need another aftermarket dipstick (Lokar) to make it work. Overall, I am happy with the pan and I no longer have the drain plug issue or the seepage at the OEM dipstick interface with the pan. I found the Lokar dipstick from Summit was the more affordable way to go.

 

[jamesroney]

From the inside:
1. eliminate M14 threads.
2. grind inner surface smooth.
3. fabricate 1/8 inch thick back up washer.
4. add plate and weld hole closed.
5. drill pilot hole.

From the outside:
6. enlarge pilot hole to 29/64
7. tap hole 1/2-20

Find a factory oil pan plug with a 7/8 head, and soft washer.

The problem with the Ford oil pan is that the back-up plate is only about 1/8 thick, and there is an added protrusion formed for the threads. This allows the threaded area to be about 3/16 inch thick, but still accommodate maximum drainage. A "normal" 1/2-20 thread in mild steel should about 7/16 of an inch thick. Ford cheats and makes the threads the absolute minimum.

When you tap it oversize, you drill thru that formed protrusion, and there's no meat left. So the only way to fix it is to actually build it up.

I will never understand why people torque the drain plug to infinity foot-lbs, just because it uses a large wrench. The spec is about 19 lb-ft. But the "normal" torque for a bolt with a 7/8 head is somewhere north of 150 lb-ft. So they get over-torqued a lot.

If you were local, I'd do it for you. But budget 0.5 hours for the job.

 

[jeremywatco]

I did buy a new pan off wild horses but didn’t fit with my larger oil pump that came on the new motor. Beat on it for a few days to try and shape it but then realized it was a losing battle so threw my old one in the parts cleaner and made it look new. Now just need to figure out this drain before I put motor back in.

 

[ntsqd]

Doan want that sumb___h leaking my engine's life-blood, so I'm gonna tighten it until my eyeballs pooch out a little!
At least, that's what I guess was going thru the mind of the gorilla who tightened it the last time.

On the Ranchero I got tired of the drain plug leaking no matter what I tried so I brazed a -8AN steel plug that I had drilled thru onto the outside of the pan. Then a -8AN cap became the 'plug'. Not sure that I'd do that on an oil pan expected to go off-road.

These days I'd add thickness to the outside of the oil pan and seal it with braze or silicon-bronze. Then use an annealed dead soft copper washer to seal it.

 

[73azbronco]

From the inside:
1. eliminate M14 threads.
2. grind inner surface smooth.
3. fabricate 1/8 inch thick back up washer.
4. add plate and weld hole closed.
5. drill pilot hole.

From the outside:
6. enlarge pilot hole to 29/64
7. tap hole 1/2-20

Find a factory oil pan plug with a 7/8 head, and soft washer.

The problem with the Ford oil pan is that the back-up plate is only about 1/8 thick, and there is an added protrusion formed for the threads. This allows the threaded area to be about 3/16 inch thick, but still accommodate maximum drainage. A "normal" 1/2-20 thread in mild steel should about 7/16 of an inch thick. Ford cheats and makes the threads the absolute minimum.

When you tap it oversize, you drill thru that formed protrusion, and there's no meat left. So the only way to fix it is to actually build it up.

I will never understand why people torque the drain plug to infinity foot-lbs, just because it uses a large wrench. The spec is about 19 lb-ft. But the "normal" torque for a bolt with a 7/8 head is somewhere north of 150 lb-ft. So they get over-torqued a lot.

If you were local, I'd do it for you. But budget 0.5 hours for the job.

do this

 

[Oldtimer]

Since my pan is off, and clean, this is what threads looks like if unmolested.