Calorifier connection 1.5 BMC

[GBW]

I introduced a engine water take-off before the thermostat but it seems to be ineffective.

 

Where do others connect please?

[David Schweizer]

On the BMC 1.5 you can use the cab heater connections, which is what most people seem to use, we connected both our calotifier and radiators to the cab heater connections and the water flow was fine. The subject was covered some years ago for the BMC 1.8 which is very similar.

 

Edited November 3, 2020 by David Schweizer

[Tracy D'arth]

 

Flow from the tapping ( 1/2" BSP) on the end of the head furthest from the front of the engine, return to the water pump connection.

[Tony Brooks]

I think some Indian heads may not have that tapping but it looks as if it could be drilled.

 

If needs must i think you could utilises the temperature sender hole in the side of the thermostat housing as a take off and T the thermal switch/sender into the feed pipe (with a suitable electrical earth if not connected to the block by metal).

Edited November 3, 2020 by Tony Brooks

[GBW]

Thanks for the responses. On my cylinder head, the head end tapping seems "most likely" to be 5/8" UNF.   A 5/8" UNF tap threads in without cutting but my plug gauge would not.  I then discovered that was left hand!  I understand from the DS steer, that there is confusion about this thread and not all engines may be the same.

 

The temperature sensing tapping is also 5/8" UNF.

 

The engine was bought on ebay dismantled as I am not happy with the power output from the existing one whose compression ratio leaves something to be desired.  The bores on the ebay purchase were well over top rebored limit, so it has been sleeved and rebored, new pistons, crank regrind etc.

 

As stated, I did take a feed from the temperature sensing fitting point and the hoses were warm but only warm.  The return was teed into the heat exchanger return.

 

It will be reassuring to run the replacement in the workshop and prove timing etc where it is convenient.

 

Thanks again.

 

 

Edited November 6, 2020 by GBW

[Tracy D'arth]

As I understood the heater connection on the 1.5D was 1/2" BSP but the 1.8D was 5/8" UNC so you may have a 1.8D head on a !.5D block!  Could this account for the compression discrepancy?

 

You may also have another tapping on the rear of the heat exchanger/exhaust manifold but you will get no heat until the skin tank is up to temperature, if you are skin tank cooled.

You could also explore using the temperature sensor connection below the thermostat, using a Teepiece ?

 

 

[GBW]

1 minute ago, Tracy D'arth said:

As I understood the heater connection on the 1.5D was 1/2" BSP but the 1.8D was 5/8" UNC so you may have a 1.8D head on a !.5D block!  Could this account for the compression discrepancy?

Both connections are UNF.  1/2" BSF feels like it will enter but, as others have said, "it will forever leak"!

 

You may also have another tapping on the rear of the heat exchanger/exhaust manifold but you will get no heat until the skin tank is up to temperature, if you are skin tank cooled.

You could also explore using the temperature sensor connection below the thermostat, using a Teepiece ?  As I said, I tried that.

The boat is a sea going sailor (although she spent a year on a canal!).  Cooling is sea water through a heat exchanger.

 

 

1 minute ago, Tracy D'arth said:

 

 

 

[Tracy D'arth]

6 minutes ago, GBW said:

The boat is a sea going sailor (although she spent a year on a canal!).  Cooling is sea water through a heat exchanger.

 

 

 

Ah, not that then.

 

Thought. is there a working thermostat fitted?

[GBW]

Yes - it was prime suspect.

[Tracy D'arth]

7 minutes ago, GBW said:

Yes - it was prime suspect.

Is the engine overcooled as well?

[Tony Brooks]

1. as you have two water pumps are you sure the return is into the ENGINE water pump inlet hose.

 

2. I can't see how/why you don't get hot water from the temperature sender hole unless you have an airlock in the calorifier circuit that is stopping all but a trickle of flow.  Long shot -  is the thermostat an old fashioned bypass stat with the outer sleeve that blocks holes in the side of the chamber  I am sure it should be an ordinary thermostat.

[GBW]

Just to make it clear, I am rebuilding a replacement engine and, while it is on the bench (actually on a fork lift so I can wind it up and down for comfort!) access is "rather better" than in the engine bay on the boat!

 

My questions relate to preparing for the changeover.

 

The existing engine is in the boat currently locked down and physically locked away until Monday next (Barry Island).  She is on the hard and I am not really interested in diagnosing and fixing.

 

With the replacement engine accessible all round and capable of being run in a controlled fashion, I am looking forward to being able to achieve correct timing and fiddling although I cannot impose a load except an electrical one.

17 hours ago, Tony Brooks said:

1. as you have two water pumps are you sure the return is into the ENGINE water pump inlet hose.  Yes.

 

2. I can't see how/why you don't get hot water from the temperature sender hole unless you have an airlock in the calorifier circuit that is stopping all but a trickle of flow.  Long shot -  is the thermostat an old fashioned bypass stat with the outer sleeve that blocks holes in the side of the chamber  I am sure it should be an ordinary thermostat.  It is.  The heat exchanger outer (i.e. containing the engine water) did always seem hot so it could be the thermostat.  Easy to fix on the new engine.

 

 

Edited November 7, 2020 by GBW

[GBW]

On 06/11/2020 at 16:02, Tracy D'arth said:

As I understood the heater connection on the 1.5D was 1/2" BSP but the 1.8D was 5/8" UNC so you may have a 1.8D head on a !.5D block!  Could this account for the compression discrepancy?

 

It is definitely UNF and there are actually three.  

 

 

 

[Rincewind]

Be very careful about this heater connection thread size on the 1.5 cylinder head.  I have 3 cylinder heads - not all on the same block of course 🙂 and have measured the threads on all three heads.

One can be forgiven to assume that being a British engineered product of the post war era that all the sizes would be imperial but it appears that this is not the case. 

Using imperial measurement, the "Nominal" size (Diameter) of the male thread is, 5/8" or - to be precise - 0.620" measured with a digital Vernier gauge. (0.625" being 5/8")

Using the 55 degree angle thread form of a thread gauge (Whitworth) the closest number of threads per inch (TPI) measured was 16. (Thread gauges above & below this number of TPI did not match).

There is NO such thread form – (5/8” x 16 TPI) in any of the imperial systems, including: - BSW, BSF, BSP, UNC. UNF, NPT or even the Japanese system of threads.

However, if you convert the "Nominal" diameter of 0.620" to metric you will find it is as close as possible to be 16mm nominal diameter. (15.74mm, measured tolerances apply)

The thread form itself, if you measure it with a metric thread gauge of 1.5mm pitch, (60 degree angle thread form) you will find it will have an almost identical TPI as the imperial equivalent. (16.93) i.e. 25.4mm divided by 1.5 = 16.93  This thread form - 16mm x 1.5 mm pitch - DOES exist.

Conclusion:-   It is therefore, a metric (Fine) thread: - 16mm x 1.5mm pitch

Further, if you purchase a 16mm x 1.5mm pitch (second) tap you may well find - as I did - that you can recut (clean up) your threads perfectly.  Do not cut all the way through with the tap, use the taper on the tap to provide somewhere for the male thread to “bite”.

A quick search on eBay will bring up numerous pipe connections for sale with this particular (metric) thread form for various nominal hose sizes.

BMC may have chosen this metric thread form rather than the coarse BSP or NPT thread form, for two (or more) reasons:-

·         it would offer a smaller footprint on the head where space is at a premium

·         It would increase the thread contact area in the relatively thin wall of the head.

Check carefully, you may well find that, someone in the past has rethreaded these ports to accommodate an alternative thread size, so be wary and do not assume the "obvious".  

This observation applies to the two ports on top of the cylinder head: - the thread underneath the thermostat housing to accommodate the temperature sensor is of a different thread form. 

Hope this helps

Rincewind