Help Identifying "Funny" Pipe Thread, Please ?

[Big Steve]

That elbow on David's engine looks like a malleable iron fitting, so it'll have 3/8" BSP male both ends. The engine builder must have run a 3/8 tap through the hole in the head.

 

If you do this, get a fitting with a 3/8 BSP taper thread, this seals much better in a 3/8 parallel hole, and with plenty of PTFE tape (use gas tape, it's thicker) it'll give you a lot of discretion in the final direction of the elbow.

[alan_fincher]

Small pipe is probably air bleed to expansion tank?

Ah, I didn't realise it was likely to have one - my old BL vehicles from the 1970s had a radiator cap, and that was it!

 

That elbow on David's engine looks like a malleable iron fitting, so it'll have 3/8" BSP male both ends. The engine builder must have run a 3/8 tap through the hole in the head.

 

If you do this, get a fitting with a 3/8 BSP taper thread, this seals much better in a 3/8 parallel hole, and with plenty of PTFE tape (use gas tape, it's thicker) it'll give you a lot of discretion in the final direction of the elbow.

OK, yes that sounds possible.

 

It's obvious from the home grown nature of what Calcutt have now sent me, that there probably is no standard solution any more.

 

Even if the thread matches, I'm struggling to see how I could use this. (The blanking plug is pictured for comparison....)

 

 

[Iain_S]

How thick is the wall of the Calcutt fitting? The fitting looks to be a fair bit wider than the thread diameter. Could the non threaded end be turned down to a more sensible size? (by a friendly local machinist )

Iain

[alan_fincher]

It's quite thick - in fact the central hole is surprisingly small, (and not very round!).

 

I'm sure what you say is possible - I could probably even post it off to my brother, who I'm fairly certain could arrange it. However there is not a lot of length, so, unless it's OK to grip those threads in a chuck (?) it would be quite hard to thin enough to push a pipe on properly and to clip it.

 

Alan

[OptedOut]

unless it's OK to grip those threads in a chuck

 

Normally you screw a nut or barrel nipple on the fitting to mount in the chuck.

[Batavia]

Alan,

 

From what you say there should be enough metal to turn it down to 15 mm and you could then fit a 15 mm x 1/2" compression stud elbow on this and then use a 1/2" female hosetail to connect to your hose.

 

This would give you adjustment on the direction it sets off from the head and would be a low-rise assembly.

 

If you have a 5/8" UNF nut to fit on the male thread, I could turn it down to 15 mm for you (despite my workshop being in a state of disarray at the minute, the lathe is temporarily set up and useable).

 

Chris G

[Hairy-Neil]

I understand what you are saying, but this doesn't look like a temperature gauge transmitter.....

 

 

(Surely even a temperature gauge sender should be before the stat, not after it, anyway ?)

 

If those pipes are not associated with a cab heater, it's hard to imagine what they are for.

 

And where's the other one going to ?

 

In an ideal world the temp gauge transmitter would be before the thermostat. Remember though that these BL engines date from the from the dark ages (early 1950s) before temp gauges were common fitment so afterthought design often comes into play. The stat is self controlling and the temp gauge is not there to protect the engine from a faulty thermostat.

 

That small pipe out of the thermostat housing will be an air bleed to the header tank. Later BL models had a low mounted crossflow radiator and needed this pipe to allow the system to vent from the highest point of the engine. That pipe also looks to be a 3/8 diameter hose, hardly adequate for a heater supply.

 

By the other pipe I guess you mean the one that disappears under the manifold? It's my guess this is something to do with crankcase ventilation.

 

Edited to say having looked at it again it could be a bypass hose?

Edited December 4, 2008 by Hairy-Neil

[wonderdust]

I would say small hose is bypass for cooling/heater, could the one that dissappears be anything to do with the fuel?

[jake_crew]

I wonder if the diagram shows the heater take-off from above the t/stat so that the engine quickly gets up to temp BEFORE the stat opens and lets hot water out to the heater. Otherwise if you had a big heater circuit the engine would take ages to warm up.

 

Y ou should be able to slip the 1/2" hose on OK If you heat it (boiling water/cup of tea?) and smooth & grease the end of the 5/8 stub. It would be better to have grooves/barbs on your stub, but the hose should still grip OK with a decent jubilee clip.

 

I note that your new stub is not the right angle you originally wanted, so you'll worry it might trap air. But I think you''ll find that the flow from the pump will push the air bubble out. I have the identical arrangement in a BMC car with A series engine, and the standard water pump will blow out air locks from at least 6" above the cylinder head.

Edited December 4, 2008 by jake_crew

[Big Steve]

I've been pondering this again today and come up with this:

 

I got a 5/8 UNF bolt to compare, the threads are exactly the same as the fitting, and even measure 1.5mm pitch with a digital caliper, which is 17 TPI

Here's a picture of the two side by side

 

I also realised that my engine has a spacer on which fits on top of the thermostat hole and allows two extra water outlets, the stat goes on top of this, then the thermostat casting. This item is a brass casting, not an home made affair , so it must be available somewhere from a marinizers. Sorry I can't help more, here's a picture

Edited December 4, 2008 by Big Steve

[wonderdust]

I also realised that my engine has a spacer on which fits on top of the thermostat hole and allows two extra water outlets, the stat goes on top of this, then the thermostat casting. This item is a brass casting, not an home made affair , so it must be available somewhere from a marinizers. Sorry I can't help more, here's a picture

 

Known as a sandwich plate.

[Hairy-Neil]

I wonder if the diagram shows the heater take-off from above the t/stat so that the engine quickly gets up to temp BEFORE the stat opens and lets hot water out to the heater. Otherwise if you had a big heater circuit the engine would take ages to warm up.

 

Doing it that way the heater wouldn't demist/defrost the windows till the thermostat opened, perhaps after 5 miles the winter. In exceptionally cold weather the heater would struggle to work.

[alan_fincher]

If you have a 5/8" UNF nut to fit on the male thread, I could turn it down to 15 mm for you (despite my workshop being in a state of disarray at the minute, the lathe is temporarily set up and usable).

Chris that's a very generous offer, (although I have no nut!).

 

However I seem to have finally scored some success with the other part, (came from ASAP supplies), which I think is secure enough, and I now seem to have got some flow despite the high point in the attached hose.

 

In an ideal world the temp gauge transmitter would be before the thermostat. Remember though that these BL engines date from the from the dark ages (early 1950s) before temp gauges were common fitment so afterthought design often comes into play. The stat is self controlling and the temp gauge is not there to protect the engine from a faulty thermostat.

In fact they do all seem to come equipped with a port for a temperature sensor, (just below the thermostat housing). Or at least all the ones I've seen - and the operation and workshop manuals dating from the age of the engine show it.

 

I wonder if the diagram shows the heater take-off from above the t/stat so that the engine quickly gets up to temp BEFORE the stat opens and lets hot water out to the heater. Otherwise if you had a big heater circuit the engine would take ages to warm up.

I thought the other was what is normally intended - to take the heater connection off before the thermostat, so that you don't have to wait for the engine to get to stat opening temperature before you get any heat. That's certainly how I've heard it explained.

 

Also my engine has a "bypass" rather than a standard stat - the type with an extra plate on a downward projecting stub, that can cover an extra hole in the bottom of the stat housing. I did research those years back, but need to refresh my memory as to just what difference this makes.

 

I note that your new stub is not the right angle you originally wanted, so you'll worry it might trap air. But I think you''ll find that the flow from the pump will push the air bubble out. I have the identical arrangement in a BMC car with A series engine, and the standard water pump will blow out air locks from at least 6" above the cylinder head.

Yes, after a more determined attempt today, I think you are right. I've finally got it circulating, even with the high point in the hose.

 

I took the boat for a couple of miles each way, as it didn't seem to want to purge it on the mooring.

 

More investigation required, but looking promising. (I got some nicely hot water, but didn't run it all off to see how much - also I'd managed to leave a thermometer at home).

 

Alan

[gazza]

holy thread resurection batman.....

 

i am in the process of getting the elysian ready for engine transplant.

have had the same problem as alan with the take off for calorifier connection, the old fitting selfdestructed on removal so cant be reused.

searching the net turned up this thread

i had resigned myself to making one out of a 5/8 unf bolt, the plan was to weld a nut to the bolt, cut off the bolt head, skim shank to 15 mm od, drill the whole lot to 13mm id and then use a 15mm compression fitting elbow to connect to existing 15mm copper pipe

 

as i am flat out at work at the mo this was going to be awkward to fit in, plus i would have had to source a 5/8 unc nut and bolt as we only use metric, i have not had the pleasure of building up a stock of bmc bolts neither....

 

so a little more searching came up with this clicky

 

MMS9-8-7

1/2BSP x 5/8UNF- steel

£2.57 (Excluding VAT at 17.5%)

 

 

i have some 1/2" bsp elbows and 1/2bsp to 15mm compresion fittings kicking about, so for 8 quid (postage is around 4 quid) i can get it fitted up without having to spend time at the tig set and lathe that i dont really have

 

result!!

[Tony Brooks]

Slightly tongue in cheek, but I almost wonder if I couldn't Araldite, (or similar), a fitting in.

 

Unlike other tapped holes on the engine, it's not something that would ever need to be removed again.

 

I think it's soluble without such a cowboy solution, but if I found the threading incapable of holding anything in in a watertight way, I might consider it.

 

 

On the hirefleet we used to drill the blanking bolt, counter drill the top a little bit and braze a length of copper pipe in so we could fit an elbow but take it off to screw the thing back in with a deep socket.

 

B&Q sell flux coated silver solder (at a price) and decent blowlamp should get the whole thing hot enough for the silver solder to run - rather than that poxy resin

[Tim Doran]

If you are haing problems with the high point, why dont you add in a bleed valve. It would make sense to allow air to escape from the highest point in the system.

 

Tim

[FadeToScarlet]

 

Just out of curiosity, what's the black thingy with the hose going into it on top of the rocker cover? Is it part of an oil-cooling system for the gearbox?

[RLWP]

Just out of curiosity, what's the black thingy with the hose going into it on top of the rocker cover? Is it part of an oil-cooling system for the gearbox?

 

Engine breather plugged into the oil filler hole.

 

Richard

[churchward]

Just out of curiosity, what's the black thingy with the hose going into it on top of the rocker cover? Is it part of an oil-cooling system for the gearbox?

It is a crude waste sump gas re-cycler in effect so that the engine consumes them and throws it out the exhaust. The oil filler cap is the black domed bit attached at the top and contains a rough gauge wire gauze to catch any lumps.