Mystery Head Bolt?

[Mr Bee]

My 1939 flathead six has normal bolts holding down the head with the exception of three mystery bolts.  As per the attached image they look like a hex nut just sitting on the head where a regular hex bolt would go.  You can see the thread inside these odd bolts but there doesn't appear to be enough of an engine stud to even grab any of the threads, or maybe barely one thread.

 

There are two at the back, drivers side, nearest the engine starter and one right in the middle.

 

Any ideas what they are and how they are fastened to the head or block?

[Plymouthy Adams]

these are for mounting accessories to the head bolts......I cannot comment on the accessory applications/location per the 1939 year.....

[Dozerman51]

These type head bolts were called “Tapped head cap screws” according to my Dodge truck master parts book. The threaded part on the head was used to attach whatever the accessory was mounted on the motor. My IND-7 Industrial head was attached to the block using this type set up. The CC# was 692857 using the parts book I have. This is a WWII parts book, so I would imagine they changed the part number in later years.

[Jerry Roberts]

I saw a Pilot House truck engine that had ALL of the head bolts tapped like this . I guess that is what was available to the man . 

[Dozerman51]

I believe you are 100% correct on that Jerry.

[dpollo]

On the 39 and 40 these were used to fasten the throttle linkage assembly  above the distributor  2 needed.   The third may have been for an air cleaner brace.

[vintage6t]

A little off topic but my Rambler uses a head bolt like that for the battery ground cable connection.

[Matt Wilson]

Some vehicles used these bolts to attach the horn. 

[Young Ed]

also used for an eyelet for the throttle return spring on some 50s models. Like Jerry mentioned for some reason the industrial 6 in Dads worthington had about 1/2 of these for it's head bolts

[Mr Bee]

Thanks for the responses...yeah, I see that makes sense using them to mount accessories.

 

If I want to take the head off, it looks like I could just use the same socket as the head bolts.  However, as mentioned in my original post, I'm not even sure if these are bolts that go into the head and block or if they are nuts that just barely thread onto studs that come up from the block.

 

Anyone know if they are nuts or bolts?  I could take a socket to them but they are so odd I don't want to break anything.

 

[Young Ed]

that is a head bolt with a threaded head. remove it like any other bolt

[greg g]

Bolt.  Using three on mine 2 for my shade tree dual carb linkage, and one for the ground strap. They are handy to have.

[Mr Bee]

Hey Ed:  any chance you can find an example of what this bolt looks like on Google?  If the "nut" which is visible is.actually the cap of the bolt, there's barely any meat connecting the cap to the bolt's shaft.

[Mr Bee]

Just found out the the bolts cap is called the head.  The shaft is called the shank.  Just in case I caused confusion with my wording.

 

Imagine taking a regular head bolt then weld a nut on top.  That would be a perfectly strong head bolt with the value added feature of allowing an accessory to be mounted into the threaded nut.

 

But these are like regular head bolts on which they tapped thread into the head making the head more like a nut.  In so doing, there simply can't be much of anything still left to keep the head onto shafts. ..or am I missing something? 

[Young Ed]

It may seem like they are weak but I've never had one snap off. 

[Mr Bee]

Just found this via Google.  Is this what it looks like?

 

Hope it's okay to make a reference to another forum.

 

http://www.pirate4x4.com/forum/attachments/shop-tools/673643d1337803824-shoulder-screw-wood-screw-tip-tap-lag-bolt.jpg

 

[Andydodge]

MrBer...yep thats what they are, a bolt with a threaded head..............I have never seen nor heard of one snapping thru that internal threaded top............. however breaking head bolts of both this type and the normal hex headed type is a common occurrence, usually happens where the head bolt goes thru the block into the water jacket, it rusts, the threads "grow'......... you go to undo the bolt ...........it turns a bit until the "grown" thread can't get thru the threaded block , you keep turning and Dah!, dah!........the bolt is loose but only half of it..........lol........its common on engines that have been sitting for a while................welcome to the wonderful world of old cars.......lol.............andyd   

[Mr Bee]

Thanks Andyd...hopefully I won't have to pull the head.

 

Reminds me, ever snap a bolt that connects the engine to the tranny? 

[Andydodge]

I haven't............engine to trans?.........where exactly?............andyd

[Mr Bee]

Sorry, I used the term tranny loosely.  I meant the bell housing.

[Andydodge]

Still nope, you'd have to be lucky....err, unlucky to do that...........lol.............andyd.

[Mr Bee]

I just searched "1939 Dodge engine" in Google and I seem to have found some engines with studs and nuts and some with bolts and or a mix.

 

Does anyone out there have a 1939 Dodge 201.3 engine?  Does it have studs that come out of the block or bolts that go into it?

[Young Ed]

The early flatheads had studs with nuts. I believe by 39 they had mostly switched to bolts but who knows what happened along the way to a given engine.