Anyone know what this is for?

[GBW]

The threaded hole next to the blanking plug (5/8" UNF).

It seems to connect to the waterways.  Is it usable for calorifier take off (in or out)?

The hole next to the blanking plug (tapped 5/8" UNF).Is it usable for calorifier take off (out or return)?

 

[Tracy D'arth]

No it is not. It is in the front of the head where there is least heat and it will bypass the thermostat directly. Use the one in the rear of the head for the flow.

[GBW]

Thanks.  What's it for then?  I could use it for an additional water temperature sensor I suppose.

[Tracy D'arth]

57 minutes ago, GBW said:

Thanks.  What's it for then?  I could use it for an additional water temperature sensor I suppose.

I didn't design it!  As I said in your other thread this engine was used in many applications. Castings often have holes left where the casting cores were and some are filled with brass plugs, others with threaded plugs.

Edited September 11, 2023 by Tracy D'arth

[Rincewind]

 

 

2 hours ago, GBW said:

The threaded hole next to the blanking plug (5/8" UNF).

I strongly recommend that you re-measure the thread and this time use a metric ruler 😉

[GBW]

Why?

I don't think metric was  very common when this engine was built!

However, the plug gauge I used which was a very nice fit in the hole, happened to be M16 fine!

It had been returned to the wrong drawer.

[Rincewind]

3 hours ago, GBW said:

I don't think metric was  very common when this engine was built!

 

I agree, metric was not very common when this engine was built. However, although most of the threads on the BMC engine are UNF or UNC, these two particular threads are metric (or they were when the head was manufactured, -  unless someone has re-threaded them).  I am referring to the two ports on top of the cylinder head that, more often than not, are blanked off with a threaded hexagon headed plug, one port of which you have indicated in your photo.  The M16 x 1.5 pitch port on the other end of the cylinder head is often used for one of the calorifier connections as Tracy has mentioned.  The reason why a metric thread was chosen, in my view, was that it provided a smaller footprint compared to a BSP thread in the limited space available and offered greater thread contact area in the relatively thin casting.

 

[Tracy D'arth]

37 minutes ago, Rincewind said:

 

I agree, metric was not very common when this engine was built. However, although most of the threads on the BMC engine are UNF or UNC, these two particular threads are metric (or they were when the head was manufactured, -  unless someone has re-threaded them).  I am referring to the two ports on top of the cylinder head that, more often than not, are blanked off with a threaded hexagon headed plug, one port of which you have indicated in your photo.  The M16 x 1.5 pitch port on the other end of the cylinder head is often used for one of the calorifier connections as Tracy has mentioned.  The reason why a metric thread was chosen, in my view, was that it provided a smaller footprint compared to a BSP thread in the limited space available and offered greater thread contact area in the relatively thin casting.

 

These tappings have changed threads over the considerable number of years that this engine has been manufactured. It is quite possible that the later Indian product has used many metric threads.

I have found UNC, UNF and BSP to be the most popular.

[magnetman]

 

Lifting eyes?

[Tracy D'arth]

45 minutes ago, magnetman said:

 

Lifting eyes?

No, they are on the rocker box sleeve nuts.

[Bod]

21 hours ago, GBW said:

The threaded hole next to the blanking plug (5/8" UNF).

It seems to connect to the waterways.  Is it usable for calorifier take off (in or out)?

The hole next to the blanking plug (tapped 5/8" UNF).Is it usable for calorifier take off (out or return)?

 

If you are asking about the hole with the screw fitted in, then that is directly under the rocker cover gasket, and should have a machined flush blanking plug.

What can be seen through the hole?

It will have been made for an internal passage which could not be cast in directly, but had to be drilled in as part of the machining processes in manufacturing.

 

Bod

[GBW]

No, it is clear of the rocker cover.

Rusty interior is visible through the hole.  There is no machined surface and it is connected to the waterways.

16 hours ago, Rincewind said:

 

I agree, metric was not very common when this engine was built. However, although most of the threads on the BMC engine are UNF or UNC, these two particular threads are metric (or they were when the head was manufactured, -  unless someone has re-threaded them).  I am referring to the two ports on top of the cylinder head that, more often than not, are blanked off with a threaded hexagon headed plug, one port of which you have indicated in your photo.  The M16 x 1.5 pitch port on the other end of the cylinder head is often used for one of the calorifier connections as Tracy has mentioned.  The reason why a metric thread was chosen, in my view, was that it provided a smaller footprint compared to a BSP thread in the limited space available and offered greater thread contact area in the relatively thin casting.

 

This engine is probably as old as I am (do the search!).

5/8" UNF is 18 tpi.  this corresponds to a pitch of 1.41mm.

For some strange reason, my elderly thread gauge, made in the USA!, does not present 18 tpi.

It does offer 1.5mm, but that doesn't quite fit. The plug is short which doesn't help.

(I am not going to fire up my 0.00001 measuring microscope1!)

5/8" diameter is 15.875mm.

I think I am going to go with 5/8" UNF.

[Tracy D'arth]

Well the tapping for the temperature sender is 5/8" UNF.

[magnetman]

Temperature sender seems likely or maybe they incorporated the option of having a screw in thermometer. 

 

I'm going to have a look at my two 1.5s and see if they have the same thing. 

[Bod]

Is it the place that the tap(water type) was fitted on the early car heaters?

Turn on in the late autumn, off in late spring.

 

Bod

[MtB]

11 hours ago, GBW said:

No, it is clear of the rocker cover.

Rusty interior is visible through the hole.  There is no machined surface and it is connected to the waterways.

 

 

 

And yet.... 

 

Your OP shows a slotted plug next to this hole which I think a lot of people took to be screwed into another hole directly under the gasket (including me!), being the one you are asking about.

 

 

 

 

[StephenA]

53 minutes ago, MtB said:

 

 

And yet.... 

 

Your OP shows a slotted plug next to this hole which I think a lot of people took to be screwed into another hole directly under the gasket (including me!), being the one you are asking about.

 

 

 

 

 

Yes that was confusing me...

[magnetman]

1 hour ago, Bod said:

Is it the place that the tap(water type) was fitted on the early car heaters?

Turn on in the late autumn, off in late spring.

 

Bod

 

Like this ? 

 

Maybe the engine is from an Austin J4. The 1.5s on one of my boats both came from Austin J4 police wagons according to the serial numbers. 

Old one on eBay.