Negative battery cable connection to block

[Sherlock]

Im trying to connect the negative battery cable to engine block on the passenger side front part of block where it was connected before engine removal and machining. Does anyone know the bolt size of the threaded hole? See arrow in attached pic. Ive tried several different sized bolts and none seem to work

 

[904Bronco]

Should be 3/8" course thread, probably need to chase the threads as it is a good dirt catcher.

 

[DirtDonk]

And because it looks freshly painted, chasing the threads is a good practice anyway. However, is it possible that this location is the unused, plugged, or unfinished hole where some engines got a block drain?
Is it possible this is a different engine block them or came out of your bronco originally?
If it ends up being anything different than what you think it is, there is sometimes another threaded hole further back along the pan rail just in front of where the starter motor is.
That’s an even better location for a grounding bolt, but would not have been used by Ford because it would require another 10 or 12 inches of battery cable.
Making it far too expensive for production purposes.

 

[Sherlock]

I do know it’s the block that came with the bronco. I started to chase the threads but didn’t have luck starting the 3/8 chaser. It almost seemed to big. Went down a size and could tell it was too small. Started to second guess myself by wondering if it was metric but was certain that couldn’t be the case since I know the block is original. It could be there is a lot of paint in there making the chaser hard to start. The block was bored .010 over and, following the guidelines from Tom Monroe’s Rebuilding SMF book, I chased all the open threads just to make sure they were open before painting. It could be i missed chasing the threads of that one. I will give it another try. If that doesn’t work, I’ll try the other location. For clarity on the other cable location, you’re not talking about the threaded plug just forward of the passenger side engine mount (that’s just behind the threaded hole I referenced in my original post)? I saw that and was wondering what it was for.

 

[904Bronco]

That is a coolant drain plug. There is one on the other side of the motor towards the back.

 

[DirtDonk]

Yeah that doesn’t look like the one I was thinking of. But the one I am referring to is on the same passenger side, just closer to the starter motor.
Maybe they are not on every block? Maybe just later models versus early?
I don’t know, but I carry a couple of studs in my electrical supply box for using that hole.
The type of studs that are about an inch long or maybe a little more and half of it is coarse thread the other half is fine thread.
Makes a perfect insert into the block and leaves the studs sticking out to put a battery cable and a nut on.

 

[jamesroney]

Im trying to connect the negative battery cable to engine block on the passenger side front part of block where it was connected before engine removal and machining. Does anyone know the bolt size of the threaded hole? See arrow in attached pic. Ive tried several different sized bolts and none seem to work

By the way, your pics are horrid. And to placate the natives...that looks like a late model roller block with Explorer serpentine.

The block ground hole is 7/16x14. I stuffed a drill in the hole to highlight the location on the Explorer block. The blue block in the pic is a non roller block.

 

[Broncobowsher]

It looks like the arrow you are pointing with is the back side of a through hole used for the accessory bracket. So there is already a bolt in the hole, just from the other side?

 

[Sherlock]

Its a 76 block with explorer serpentine. As mentioned earlier, it is the block that came with the bronco

 

[DirtDonk]

I took your words as meaning just that, but your wording could actually mean anything.
By “came with the bronco“ it could mean it came with it originally from the factory, or it just happens to be the engine that was in it when you bought the bronco more recently.
If you’re not the original owner you might not know. It could have been one of many swapped in engines installed over the last 45 years or so.
Or however many years before you bought it.

Of course, if you are the original owner then you would certainly be in a position to know.

 

[Sherlock]

Understood. i shouldve clarified, its the original 302 block that came with the 76 bronco from the factory.

Broncobowsher makes a good point that the accessory hole looks like it mates perfectly with the explorer serp accessory bracket. Theres not a bolt coming from the other side. I just got back from looking at my father in laws 69 bronco with the original 302 and his has that same block mounting point and his battery negative cable attaches to the block at that point.

 

[gr8scott]

It actually is a through hole...I never noticed. Mine doesn't look threaded on that side. Could just be crusted up.