Help Identifying "Funny" Pipe Thread, Please ?

[OptedOut]

Best job is to run a 3/8 BSP tap through and get a brass M/F elbow and bit of good old fashioned hemp/Boss white/Stag to seal it.

[Iain_S]

I could easily be out by 1 on the count of threads per inch.

 

As I understand it, we are looking for a fitting about 5/8" or 16mm diameter, with a thread pitch of 16 - 18 tpi.

 

IMHO, the possibles are M16 conduit, or 5/8" UNF, which is 18TPI. The mangled fitting may have been caused by forcing a threaded conduit into a UNF threaded hole. It seems much more likely that the original was UNF.

 

Is it possible to borrow a 5/8" UNF tap, and try running it through the hole? Alternatively, do you know any local engineers (or mechanics ) who can cut a 5/8" UNF thread?

 

Iain

[Timleech]

As I understand it, we are looking for a fitting about 5/8" or 16mm diameter, with a thread pitch of 16 - 18 tpi.

 

IMHO, the possibles are M16 conduit, or 5/8" UNF, which is 18TPI. The mangled fitting may have been caused by forcing a threaded conduit into a UNF threaded hole. It seems much more likely that the original was UNF.

 

Is it possible to borrow a 5/8" UNF tap, and try running it through the hole? Alternatively, do you know any local engineers (or mechanics ) who can cut a 5/8" UNF thread?

 

Iain

 

If you can't find an obliging engineer or machinist , get a 5/8" UNF setbolt, drill a 10mm hole through the middle and weld or braze the pipe fitting of your choice onto the head.

If it's a high tensile bolt, don't chuck it in water to cool it after welding

Use a Dowty washer under the head when you screw it in.

 

Tim

[Hairy-Neil]

A further confusion is that a manual for the BL engine shows a thermostat housing with a second take off, implying that in some applications a heater feed was connected there, rather than directly to the head. It's never simple!

 

The hole on the thermostat housing would have been for a temperature gauge transmitter. The idea with the automotive engine is for the cab heater to work as the radiator until such time as it can no longer cope, then the thermostat opens and brings the main radiator into play. It would be pointless taking the outlet to the heater from after the thermostat.

[Big Steve]

I took the fitting out of my spare engine today. It measure the same as yours, 15.8mm dia, 1.5mm pitch (.058").

I've touted it round all the local engineering shops and can tell you it's not 16mm, it's not 3/8 BSP. A 3/8 UNF nut screws onto it ( so do 16mm and 3/8 BSP but they are very slack, and they won't even start in the hole in the head) and is nice and tight. I haven't got a 5/8" UNF bolt to try in the hole, but it looks favourite to me.

 

None of the local plumbers merchants had anything like it.

 

If you're stuck I could get a 5/8" bolt from the engineers supplies, drill it out and braze a 15mm copper stub on it. You could then use a push fit fitting on it which would allow you to rotate it to whatever direction you like. Alternatively get a 3/8 BSP tap and run it through the hole (having bored it out to the threading size first) The threads are so close the tap will force the old thread to the right size. You can get fittings 3/8 BSP to 15mm, then solder a bit of pipe in.

 

Here's a photo of the "adaptor" which came out of mine, no you can't have it!

Edited December 2, 2008 by Big Steve

[OptedOut]

Looks like a modified 1/2" Wade fitting?

Edited December 2, 2008 by OptedOut

[Timleech]

Looks like a modified 1/2" Wade fitting?

 

I think it's intended to take a thermometer bulb.

 

Tim

[Big Steve]

Further to this, I've been rechecking, and I'd made a simple mistake in the arithmatic, (I didn't have my calculator handy and by long division made it 15 tpi!) With the calculator it comes to 17.24 tpi and .622" diameter. Considering there are only 4 threads to measure, that can be taken to be 18TPI and allowing for a bit of wear and tear the diameter could be .0625", ie definately UNF.

 

What's a Wade fitting?

[OptedOut]

What's a Wade fitting?

 

Trade name, the type used on gas etc.

 

 

http://www.deltafluidproducts.co.uk/wade/products/

[Big Steve]

What about one of these then, £5 from Car builder Solutions part number ht5819, 5/8 UNF to 19mm hose fitting

 

http://www.cbsonline.co.uk/hosetail-58-unf...5819-1871-p.asp

 

 

 

 

 

[jake_crew]

Big Steve's first picture is surely a "special" made from a brass union and some copper tube.

 

I'd go with the "re-tap to a more convenient size" idea.

 

The head is cast iron and will machine beautifully. Due to the granular nature of the iron, its really best with a coarse thread, so try either standard metric or BSP. Bear in mind BSP comes in taper and parallel varieties.

 

On an old BMC car, the bypass hose stub (under the thermostat) needed replacing. It had rusted away and wouldn't unscrew, so I drilled the broken stub out. This was undoubtedly some old & imperial size so the nearest tap I could find to match the new hose stub was M16 x 1.5, which did the job perfectly. Even this was not a common size and it cost me £35 and I've used it once !

 

You can borrow it if it helps but its ~ 15mm shank so won't fit in a standard Black and Decker- I'm in Herts too.

Edited December 2, 2008 by jake_crew

[alan_fincher]

Steve,

 

You are a star - thanks for going to so much trouble.

 

5/8" UNF does sound a good bet, (I couldn't see why a 1970s British engine would contain metric).

 

At the moment there is a part in there (ASAP supplies), but it's not that tight a fit, and I resorted to a lot of PTFE tape.

 

I've returned the part that Calcutt Boats sent me, (apparently for a Turkish BMC), and am hoping they will send me what they think goes in a British BMC.

 

I'll measure that up carefully when it comes, as I'll not disturb what I've fitted until I think I have something better.

 

What I really want is something that goes straight to a 90 degree elbow, as a hose pushed on to a straight connector is raising the hose too high, so it's above the coolant level in the header tank. I know they exist for a BMC 1500, as a forum member has one, but I'm not sure about on the 1800

[alan_fincher]

This demonstrates the other problem I need to try and solve.

 

As you can see, once pushed over the vertical take off on the cylinder head, it's not currently possible to keep the heater hose feeding the calorifier below the level of the coolant in the header tank. That's the tank the hose is currently hooked over, and the level of coolant in there should only be about half way up, to allow for expansion.

 

Ideally I need to get a 90 degree elbow in there instead. (If you try and bend the heater hose too tightly, it collapses and restricts the flow).

 

I'm not sure it can be made to work as it is, as you can't easily get trapped air out the highest point of the hose.

 

Does anybody have any suggestions, please ?

 

 

For completeness, here's what the feed and return to the calorifier look like on the side of the engine that's a pig to get to.

 

[Batavia]

This demonstrates the other problem I need to try and solve.

 

As you can see, once pushed over the vertical take off on the cylinder head, it's not currently possible to keep the heater hose feeding the calorifier below the level of the coolant in the header tank. That's the tank the hose is currently hooked over, and the level of coolant in there should only be about half way up, to allow for expansion.

 

Ideally I need to get a 90 degree elbow in there instead. (If you try and bend the heater hose too tightly, it collapses and restricts the flow).

 

I'm not sure it can be made to work as it is, as you can't easily get trapped air out the highest point of the hose.

 

Does anybody have any suggestions, please ?

 

On smaller hoses tails, I have turned down the barbed part to a standard pipe size and then fitted a compression elbow.

 

This might work for you, depending on how much meat there is on the fitting you have.

 

Chris G

[OptedOut]

Looking at the high point I would think it would be purged of air before the thermostat opens?

 

Edit: BSP M/F elbow, much easier to borrow a tap for.

 

http://images.google.co.uk/imgres?imgurl=h...v%3D2%26hl%3Den

Edited December 2, 2008 by OptedOut

[Timleech]

This demonstrates the other problem I need to try and solve.

 

As you can see, once pushed over the vertical take off on the cylinder head, it's not currently possible to keep the heater hose feeding the calorifier below the level of the coolant in the header tank. That's the tank the hose is currently hooked over, and the level of coolant in there should only be about half way up, to allow for expansion.

 

Ideally I need to get a 90 degree elbow in there instead. (If you try and bend the heater hose too tightly, it collapses and restricts the flow).

 

I'm not sure it can be made to work as it is, as you can't easily get trapped air out the highest point of the hose.

 

Does anybody have any suggestions, please ?

 

If you've established that it's 5/8" UNF (see post no 9 ), and trapped air is likely to be an issue, and if Calcutt don't come up with a ready-made solution......

 

Get a fitting made up with 5/8" UNF male one end, 3/8" BSP male the other. If you're stuck on that, give me a shout. Then fit a 3/8" BSP tee onto the top of that, with the branch to the side. A plug in the top will allow for air to be vented, and a hose barb in the side for your calorifier/heater hose. The last three fittings are easily bought.

 

Tim

[alan_fincher]

If you've established that it's 5/8" UNF (see post no 9 ), and trapped air is likely to be an issue, and if Calcutt don't come up with a ready-made solution......

 

Get a fitting made up with 5/8" UNF male one end, 3/8" BSP male the other. If you're stuck on that, give me a shout. Then fit a 3/8" BSP tee onto the top of that, with the branch to the side. A plug in the top will allow for air to be vented, and a hose barb in the side for your calorifier/heater hose. The last three fittings are easily bought.

 

Tim

Thanks Tim,

 

I acknowledge the post 9 bit, but somebody in a different thread had said that the hole on top of the head is a different thread from that near the thermostat housing used for the temperature sensor, and that the latter was 5/8" UNF.

 

At the moment 5/8" UNF sounds favourite, doesn't it ?

 

Obviously I need to do some more measuring, but I'm not planning to unscrew the ASAP supplies part until I have a Calcutt bit in my hand that looks like it's any sort of match for the blanking plug.

 

I hope I'll not end up stuck, but if I am, may well get in touch.

 

Alan

[Big Steve]

If you get a fitting with an elbow, how are you going to screw it in, the rocker cover will be in the way. If you take the cover off there may well be rockers in the way, and when you've screwed it in, it may not point in the right direction.

 

Temperature sensors as standard, are /where 5/8 UNF.

 

I think I can get hold of a 3/8" BSP tap to loan you if you need to change the thread in the head.

[alan_fincher]

Agreed - nothing can be done with the rocker cover on, and I can't recall how close the rockers are to the end, (pretty close I'm guessing, as the cover is a major fight to remove).

 

It may not be possible to put an elbow, (or an adaptor with a tee), on, although if I can borrow this pic of David Schweizer's 1500, it seems to definitely have an elbow...

 

 

As I said, I need to look again, and would be now if it weren't so blooming cold that I'm delaying going to the boat!

 

EDITED: To get image displayed rather than as a link

Edited December 3, 2008 by alan_fincher

[OptedOut]

The pic on page 4 looks like it gives an idea of the hole to pushrod clearance.

 

http://www.calcuttboats.com/pdfs/Handbook%...&%201.8.pdf

[alan_fincher]

Well the alternate Calcutt part is now with me, and I'm not too optimistic.

 

Unlike the previous one, (which was barbed), this one is decidedly home grown, being machined from a piece of mild steel rod about 5/8" (or 17mm) diameter.

 

It's simply got a thread cut on one end, a hole down the middle, but the bit you are supposed to attach the hose to is the original bar.

 

God knows if I can get half inch heater hose on a 5/8" stub.

 

But it also measures up as only .600" over the threads, (too small for 5/8" UNF ?), and I still calculate the TPI as 17, not 18.

 

Oh, and the invoice says BMC 1500, not BMC 1800.

 

I doubt this is a better match to the engine than the part received from ASAP - I think I need to go and reassess!

[David Schweizer]

Alan, I have sent an email (and picture showing the required part) to the engineer who re-built my engine to ask if he can offer any advice, I will let you know if he can offer any suggestions.

Edited December 3, 2008 by David Schweizer

[alan_fincher]

Alan, I have sent an email (and picture showing the required part) to the engineer who re-built my engine to ask if he can offer any advice, I will let you know if he can offer any suggestions.

Thanks David,

 

I've yet to establish if the British 1.5 and 1.8 should use the same thread.

 

But there's even a suggestion that my Calcutt rebuilt 1.8 might have a 1.5 head on it.

 

Unfortunately some other things didn't go to plan today, so I've not been able to reassess the situation.

 

Well other than comparing the fitting Calcutt sent me this morning to the internal bore of 1/2" heater hose. Not a hope! - It's closer in diameter to the outside measurement of the hose, and no amount of forcing is likely to make it fit.

[alan_fincher]

The hole on the thermostat housing would have been for a temperature gauge transmitter. The idea with the automotive engine is for the cab heater to work as the radiator until such time as it can no longer cope, then the thermostat opens and brings the main radiator into play. It would be pointless taking the outlet to the heater from after the thermostat.

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 ?

 

Perhaps someone more clued up than I am can tell us exactly what's what in this drawing.

 

(Source: Austin Morris Power Systems: 1.8 Litre Diesel Engine Repair Operation Manual - BL Cars Limited - 1979)

 

EDIT: And yes I have noticed that in that workshop manual they are using some "generic" pictures - well I hope so, anyway - my BMC 1800 diesel is decidedly short on spark plugs, but has injectors and heater plugs that are not on the above picture!

Edited December 3, 2008 by alan_fincher

[OptedOut]

The temp sender is the bit below the thermostat, you can see half of it in the bottom of the pic, ( almost below the figure 4).

Small pipe is probably air bleed to expansion tank?

Edited December 3, 2008 by OptedOut