12G202 Head. Beyond salvage?

[Bill_qaz]

I just might get away without having to go to a machine shop. I cannot measure threads so I do not know what thread the bypass adapter I have is. Whatever it is it does not fit the cylinder head properly (it is too loose) and leaks. It screws in easily (too easily) and is clearly not watertight.

Minispares sell a bypass adapter that they say is 5/8" UNS 18 tpi "Whitworth fine" but they also say some customers fit what is actually a servo adapter that is 5/8" 18 tpi UNF. I have ordered both and will see if they fit. If not, head comes back off and I'll take it to a local engine business.

Phil already told you I previous post
It's whitworth not unf
viewtopic.php?p=691688&hilit=Bypass#p691688
Stephen

[svenedin]

I just might get away without having to go to a machine shop. I cannot measure threads so I do not know what thread the bypass adapter I have is. Whatever it is it does not fit the cylinder head properly (it is too loose) and leaks. It screws in easily (too easily) and is clearly not watertight.

Minispares sell a bypass adapter that they say is 5/8" UNS 18 tpi "Whitworth fine" but they also say some customers fit what is actually a servo adapter that is 5/8" 18 tpi UNF. I have ordered both and will see if they fit. If not, head comes back off and I'll take it to a local engine business.

Phil already told you I previous post
It's whitworth not unf

Stephen

Yes indeed but I do not know what the actual thread is in this cylinder head is (it may well have been re-tapped). All I can do is try a few adapters and seen if one fits (and does not leak).

[Bill_qaz]

Is that a typo in your previous post? 5/8 uns did you mean 5/8 unf which is 18 tpi
People often get mixed between UNC and whitworth as they are both course thread but not interchangeable the thread in the head should be a corse thread.
Loctite do a thread seal which is good when threading into water jackets

[svenedin]

Is that a typo in your previous post? 5/8 uns did you mean 5/8 unf which is 18 tpi
People often get mixed between UNC and whitworth as they are both course thread but not interchangeable the thread in the head should be a corse thread.
Loctite do a thread seal which is good when threading into water jackets

I meant what it says here: http://www.minispares.com/product/Class ... o%20search

[philthehill]

Just to reiterate the correct thread for the bypass hose stub is 5/8" x 16 TPI Unified Special which has a Whitworth form.
If you try and cut a 5/8" x 18 TPI in the head to overcome problems with the 5/8" x 16 TPI bypass stub threads you may well end up with no threads.
It is well worth purchasing a 5/8" x 16 TPI tap for special requirements like the bypass stub. It also fits the crankshaft starter dog / pulley bolt. I would not be without the one I have.

[svenedin]

Just to reiterate the correct thread for the bypass hose stub is 5/8" x 16TPI Unified Special which has a Whitworth form.
If you try and cut a 5/8" x 18 TPI in the head to overcome problems with the 5/8" x 16 TPI bypass stub threads you may well end up with no threads.

OK well the Minispares part I have ordered is the correct thread (assuming of course the thread in the head is correct and undamaged).

[Bill_qaz]

Yet they sell a tap and call it whitworth
http://www.minispares.com/product/Classic/TOOL20.aspx

I believed UNS was unified special do you have a thread guage you could check what thread is actually in your new head
They are cheap and useful, such as
https://www.ebay.co.uk/itm/334910297423 ... media=COPY

[philthehill]

Whitworth form not pure Whitworth.

[svenedin]

I never thought it was all so complicated. Part of the joys of an old car I suppose but I was not having thoughts of joy having spent hours in the garage until my back was killing me only to find a leak from something seemingly so simple! Really a bit tedious as I was taking the car to a show tomorrow at a riding school for disabled children but now that cannot happen all down to a little pipe. Never mind! Thanks for all the learned advice.

Stephen

[paul 300358]

Are you sure that its the by-pass stub that's leaking? I was under the impression that if you try to fit the copper coolant pipe above the head nuts, it was too short to correctly fit the bottom hose.

[svenedin]

Are you sure that its the by-pass stub that's leaking? I was under the impression that if you try to fit the copper coolant pipe above the head nuts, it was too short to correctly fit the bottom hose.

It is definitely the bypass stub but you’re right about the copper heater pipe. I tried to fit it above the head nuts on my first attempt and I was not happy with connection to the bottom hose. The second time round I fitted the heater pipe in the normal way which ensures there is enough copper pipe protruding into the bottom hose.

Stephen

[svenedin]

Whilst waiting for the new bypass stub pipe (which may or may not solve the problem), I took the advice given here and cleaned the block up better.

I used liberal WD40, a window scraper (a Stanley blade mounted in a handle designed to remove paint from glass) and a green pot scourer. The WD40 lubricates and loosens the carbon.

Using the scraper blade I could feel that some of the stud holes do indeed have pulled up threads. Phil you are spot on (as usual) and I will lighly countersink as you suggest. Bill: I. cleaned up the piston crowns.

Block is as original and has never been skimmed. Stamped with "2" in various places. Pistons marked "MOWOG". No lip I can feel on the bores but rather polished looking and honing marks hard to see.

Thanks agin for the invaluable advice.

I am not so upset now about the leaking stub pipe because the end result if going to be that I do a much better job and I am learning a lot. Everything happens for a reason they say.......

Stephen

IMG_9362.jpeg (2.24 MiB) Viewed 18387 times

[svenedin]

Here's one of the pulled up stud threads

IMG_9362.jpeg (213.82 KiB) Viewed 18384 times

[svenedin]

Phil, after lightly countersinking would you run a tap down each of the engine block stud holes? If yes, is the correct tap 3/8" 16 tpi UNC?

Stephen

[philthehill]

Yes I would run a 3/8" x 16 TPI UNC parallel/plug tap down the stud holes in the block.
If you have not got a compressed air blow gun to clean out the threads after tapping smear the tap with grease before tapping. The grease picks up the displaced crud.
You should only clean the centre of the piston of carbon. Leaving an outer ring of carbon helps to stem oil usage.

[svenedin]

Yes I would run a 3/8" x 16 TPI UNC parallel/plug tap down the stud holes in the block.
If you have not got a compressed air blow gun to clean out the threads after tapping smear the tap with grease before tapping. The grease picks up the displaced crud.
You should only clean the centre of the piston of carbon. Leaving an outer ring of carbon helps to stem oil usage.

Thanks I will know to only clean the centre of the piston for next time. I don't have compressed air but I do have air in a can which is reasonable but not as powerful.

Stephen

[Bill_qaz]

Whilst waiting for the new bypass stub pipe (which may or may not solve the problem), I took the advice given here and cleaned the block up better.

I used liberal WD40, a window scraper (a Stanley blade mounted in a handle designed to remove paint from glass) and a green pot scourer. The WD40 lubricates and loosens the carbon.

Using the scraper blade I could feel that some of the stud holes do indeed have pulled up threads. Phil you are spot on (as usual) and I will lighly countersink as you suggest. Bill: I. cleaned up the piston crowns.

Block is as original and has never been skimmed. Stamped with "2" in various places. Pistons marked "MOWOG". No lip I can feel on the bores but rather polished looking and honing marks hard to see.

Thanks agin for the invaluable advice.

I am not so upset now about the leaking stub pipe because the end result if going to be that I do a much better job and I am learning a lot. Everything happens for a reason they say.......

Stephen


IMG_9362.jpeg

Confused me Stephen as I never mentioned piston crowns? But the block face looks better after your cleaning.
Hope it all goes back together successfully for you this time.

The number 2 next to the bores is likely the manufacturer grade mark for cylinder bore sizing, even std bore have a tolerance/ range

[svenedin]

Whilst waiting for the new bypass stub pipe (which may or may not solve the problem), I took the advice given here and cleaned the block up better.

I used liberal WD40, a window scraper (a Stanley blade mounted in a handle designed to remove paint from glass) and a green pot scourer. The WD40 lubricates and loosens the carbon.

Using the scraper blade I could feel that some of the stud holes do indeed have pulled up threads. Phil you are spot on (as usual) and I will lighly countersink as you suggest. Bill: I. cleaned up the piston crowns.

Block is as original and has never been skimmed. Stamped with "2" in various places. Pistons marked "MOWOG". No lip I can feel on the bores but rather polished looking and honing marks hard to see.

Thanks agin for the invaluable advice.

I am not so upset now about the leaking stub pipe because the end result if going to be that I do a much better job and I am learning a lot. Everything happens for a reason they say.......

Stephen


IMG_9362.jpeg

Confused me Stephen as I never mentioned piston crowns? But the block face looks better after your cleaning.
Hope it all goes back together successfully for you this time.

The number 2 next to the bores is likely the manufacturer grade mark for cylinder bore sizing, even std bore have a tolerance/ range

Thanks. No you didn’t mention piston crowns but they were so coated in crud I felt compelled to clean them. It was like cleaning up an old chip pan. Doesn’t all that carbon create hotspots? I had noticed the engine would sometimes run on. This engine hasn’t been touched in 34 years minimum….

I am hoping that the problem with the bypass stub pipe is a matter of a thread mismatch and that the new part arriving tomorrow will fit properly. I bought the stub pipe that leaks from a Mini supplier on eBay thinking I was being clever getting a stainless steel pipe. The thread was not specified. Either the thread on the pipe is incorrect or the thread in the head is damaged. I looked at the correct tap for that pipe but it is expensive for a tool I may only use once. I decided that if the new pipe does not remedy this problem I’ll go to an engine specialist. There is a firm nearby familiar with A-series engines.

Yes each bore is marked “2” and so are the pistons

Stephen

[svenedin]

New bypass adapter parts arrived this morning.

In the photo from left to right: 1) eBay Mini "specialist" 2) Minspares 3) ESM

Using a caliper, the part that does not fit is 0.568" in diameter but both the Minispares and ESM parts are 0.572" in diameter (ignoring the threads, measured at the bottom of the thread). Quite apart from the thread, it is simply not the right size!!

I have done a trial fit in the cylinder head. The Minspares and ESM parts both fit. Neither will screw in all of the thread so I would use some thread seal to be sure. The ESM has a hex which would make insertion and removal much easier. The Minispares is longer and in theory designed to allow a new bypass hose to be fitted by sliding the hose all the way up on the bypass adapter and then sliding it back down onto the water pump outlet this avoiding having to take off the head or water pump. In practice, the gap between water pump outlet and bypass adapter is so small it is practically impossible to get the pipe in. Conclusion: I will fit the ESM part and I am going to order another two more of them for my stocks of parts as the hex is a real bonus.

Stephen

IMG_9368.jpeg (1.55 MiB) Viewed 18303 times

[philthehill]

Could you please post a current part number for the stub with hexagon.