Oil drain not drilled in cylinder head?

[Johnnyb]

So this is a strange one, took the valve covers off my friends 75 302 (motor of unknown age or origin) and discovered that the drain hole was missing on one end of one cylinder head.
As soon as the valve cover came off about a quart of oil drained on the shop floor. The missing hole happens to be at the back of the motor, the lower end, so the valve cover is filling up with oil either until it drains down the push rods or finds its way to the front hole.
In the photos below you can see the missing hole, some numbers, and then the drain hole where it should be and where it is in both positions on the other cylinder head.
Has anybody heard of anything like this?

 

[jamesroney]

So this is a strange one, took the valve covers off my friends 75 302 (motor of unknown age or origin) and discovered that the drain hole was missing on one end of one cylinder head.
As soon as the valve cover came off about a quart of oil drained on the shop floor. The missing hole happens to be at the back of the motor, the lower end, so the valve cover is filling up with oil either until it drains down the push rods or finds its way to the front hole.
In the photos below you can see the missing hole, some numbers, and then the drain hole where it should be and where it is in both positions on the other cylinder head.
Has anybody heard of anything like this?

That is SO COOL!!! It's always fun to see a factory goof like that.

That head is a D5OE-6090-A3B cast on September 12 of 1974 for the 1975 year model. If your friend has a 75 Bronco with the last 6 digits of his VIN V5xxxx or V6xxxx then it is the correct head.

I've never found a goof like that, but it's no big deal. If I owned it, I would just drill the hole. (But I have a pretty good milling machine for drilling holes.) Second choice, I would swap sides, and make sure that the drain hole is in the rear. I don't think a small block ford actually needs two drain holes. The vast majority of the oil drains down the rear hole.

That engine looks re-built. I would bet that the "bad" head was on the passenger side when it left the factory, and ran just fine for 40 years. You might not need a drain hole in the front, but the rear one needs to be there.

 

[Johnnyb]

That is SO COOL!!! It's always fun to see a factory goof like that.

That head is a D5OE-6090-A3B cast on September 12 of 1974 for the 1975 year model. If your friend has a 75 Bronco with the last 6 digits of his VIN V5xxxx or V6xxxx then it is the correct head.

I've never found a goof like that, but it's no big deal. If I owned it, I would just drill the hole. (But I have a pretty good milling machine for drilling holes.) Second choice, I would swap sides, and make sure that the drain hole is in the rear. I don't think a small block ford actually needs two drain holes. The vast majority of the oil drains down the rear hole.

That engine looks re-built. I would bet that the "bad" head was on the passenger side when it left the factory, and ran just fine for 40 years. You might not need a drain hole in the front, but the rear one needs to be there.

Thanks @jamesroney!

 

[pcf_mark]

if I did not see the picture I would not have believed it. The holes are machined in a gang fixture that is hitting a lot of holes all at once. The individual tool must have broken off and was not discovered. No chance the hole is just full of crud or a broken parts and the oil is just hiding it?

That engine must use oil like a crazy since the valve cover is filling and it is just going to overwhelm the valve seals.

 

[Johnnyb]

if I did not see the picture I would not have believed it. The holes are machined in a gang fixture that is hitting a lot of holes all at once. The individual tool must have broken off and was not discovered. No chance the hole is just full of crud or a broken parts and the oil is just hiding it?

That engine must use oil like a crazy since the valve cover is filling and it is just going to overwhelm the valve seals.

Surprisingly, it wasn't burning oil, but it was leaking profusely out of that valve cover.

 

[Broncobowsher]

I've heard of a Model T carburator that didn't have one of the circuits drilled. There was some shade tree engineering/tuning to make it run decent. Ran like that for 80 years before being discovered.

 

[spap]

Did it start leaking after the rebuild.,

 

[Johnnyb]

Did it start leaking after the rebuild.,

My friend acquired this Bronco more than 10 years ago and put it in the garage. It's probably got a few thousand miles on it and has always leaked since she's had it.
This year she decided to start working on it and one of her priorities was fixing the oil leaks.
In general it's a strong runner and I always assumed it was a rebuilt motor. There's no varnish or crud in any of the valleys and most of the gasket surfaces come apart with RTV. I think @jamesroney is correct and that the heads probably swapped sides during the rebuild.
I had to work late yesterday so I didn't make it to the shop to check the VIN number, but it looks like it has the potential of being a numbers matching head.
The decision has been made to pull that cylinder head and drill it for the passage. The other cylinder head, the one with both passages, is on the passenger side and has air conditioning and all kinds of accessories bolted to it and would increase the hours of the job drastically. I will let everyone know how it goes and what we find inside once the cylinder head is off!

THX,
JB

 

[jckkys]

There isn't a right or left side head. So just swap them out. The last builder/re-builder must have done that not knowing they created this problem.

 

[Johnnyb]

So quick follow up here, I got the head off and to the machine shop and when they were drilling out the hole they discovered the factory tool had broken off and remained in the head!
Problem now resolved.

 

[Timmy390]

WOOOOOW

Tim

 

[spap]

Great story, some poor guy was behind on drilling holes and said next

 

[Tiko433]

That’s exactly what pcf Mark said . There are some smart dudes here .