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Post by paddymk2 on Jan 17, 2018 11:54:20 GMT
I totally appreciate this level of advice
Paddy
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Post by tommydp on Jan 17, 2018 12:59:20 GMT
Hi!
Dave is right. You must have a working PCV system, either a Smith's valve or connected to the carburettor as on later models. Otherwise you could blow oil seals and the engine won't function properly as it has impact on the mixture.
If the connection for the Smith's valve (or carburettor connection if it originally had this system) has been blocked, which I assume as it runs at all, the mixture will be way too rich at the correct setting for the engine. So you would have had to weaken the mixture far beyond the base setting to make it idle well. And the weak mixture makes it run hotter. That's my guess:-)
Correctly adjusted the jet should be around 1.5 mm (0.060 inches?) below the bridge in the carburettor.
Good luck!
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Post by dave1800 on Jan 18, 2018 1:13:42 GMT
Hi Paddy
It would be helpful if you could post some photos of the crankcase breather and pipe - is this blocked off or open, also the manifold where the PCV valve fits to show how / if this is fully blocked off and also the carb where it bolts to the manifold to show whether there is a vacuum feed.
UK cars did away with the PCV in 1972 with a direct feed to the carb. UK MGBs changed from the PCV in 1969 to the direct feed to the carb(s. I'm not clear when /if there was a changeover in Australia as you did not have Mk111 cars, but were ahead on other change such as using alternators.
As the temperature dropped at idle when you richened the mixture this suggests a vacuum leak which may or may not be related to the PCV mod. The manifold vacuum is at its highest at idle (and on the over-run) so that is where any leak will be at its highest and have the greatest impact on mixture.
David
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Post by paddymk2 on Jan 19, 2018 13:59:53 GMT
Hi David, Here's some photos general view - there is a brass blanking nut where I guess the PCV was. Adjacent is the tube going to the brake booster. The small black tube is across the valve cover to the distributor. A view of the tube coming out of the top of the oil separator thing on the back of the engine. This crosses over to the radiator shroud and joins an open copper pipe that dangles down to the sump guard area as a draft tube. Presentation1.pdf (82.72 KB)  |
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Post by Penguin45 on Jan 19, 2018 15:23:45 GMT
Spigot fitting for the hose or PCV valve on the manifold is 12H1405. Seems to be available from MGB outlets.
Chris.
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Post by dave1800 on Jan 20, 2018 1:29:10 GMT
Thanks for the photos. The dangling pipe won't provide any of the necessary vacuum for crankcase ventilation until the car is travelling fairly fast; in many countries it would be illegal as it was a major source of vehicle emissions when this system was used - typically up to the early 60s.
Next step is to get the PCV and fittings; also check that you have the vented oil filler cap as the PCV won't work without it. We can then try and talk you through the tuning etc if the overheating is still an issue.
Worth checking you have the correct SU needle; I will try and find the number if you don' have it. (Mk11 Oz cars used a slightly richer needle than UK vehicles I believe.
It looks nice under the bonnet from your pics!
regards
David
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Post by paddymk2 on Jan 20, 2018 1:39:16 GMT
Thanks David
I've just ordered the valve and fittings.
Is there more to do than just connect the valve to the manifold and the mist eliminator thing?
That mg reference was good and nicely written.
On the carburettor the book indicates 3 (HS6) options for the Australian car - standard ZH, Rich TW, Weak CIW
How do I know what I've got - is it marked on the needles?
Regards
Paddy
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Post by tommydp on Jan 20, 2018 10:16:32 GMT
The engine and bay looks very nice!
Great that the valve is on its way. Just connect the valve to the manifold, and the hose from the oil separator to the valve. And it's very important the oil cap is vented, as Dave has pointed out.
You,ll have to remove the needle from the carb piston to observe the marking, on its shank.
While waiting for the PCV valve I'd make sure mechanics and ignition is ok. Valve clearances, points gap, leads, plugs, static timing.
T
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Post by dave1800 on Jan 20, 2018 14:48:46 GMT
Hi Paddy The info I have shows that the standard needle for Mk1 Oz cars is the same as the UK - TW but the Mk11 Oz cars used needle SL not ZH which was the UK spec. See SU carb needlesPlenty of interesting reading here if you've not seen it before. David |
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Post by paddymk2 on Jan 21, 2018 0:55:57 GMT
Thanks Tommy - I did go through and replace those items - I'm happy with the static timing, and did my best on the valve clearances (but probably it will get another go in the near future.)
Thanks David
Yes that is a wealthy site.
Patrick
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Post by dave1800 on Jan 23, 2018 5:40:49 GMT
We didn't answer this one for a good reason! A modern engine monitors the ambient air temperature, water temperature and oil temperature. Some high performance vehicles also sense the exhaust gas temperature. There are a number of videos on YouTube showing various parts of the engine using thermal imaging cameras as the engines start from cold to being fully warmed up, but with the vehicles stationary. There are huge changes across the block and head so it is impossible to give you an answer! However, the water temperature is a good indicator of the state of engine tune and the efficiency of the cooling system. It's also easy to check. The Crab temperature gauge isn't a precise instrument which is why I suggested earlier that you may wish to try and calibrate it with a digital/analogue thermometer. Remember that the sensor is not linear so a small increase in water temperature above normal may move the needle noticeably. "Normal" for these cars may be slightly below or above the "N" when tuned properly. I always investigated any sudden changes from the usual position, for example I noticed the needle move from just below N to N and found a pin hole leak in the heater hose sufficient to drop the pressure but hardly release any water. David Also meant to say: I really like the idea of a couple of thermocouples on the engine. What temperature would you expect the block or head to get to? Paddy |
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Post by paddymk2 on Jan 26, 2018 5:07:10 GMT
Hi All
I checked and cleaned the carby. The needle is SL and looks nice. There was a bit of baked on stuff in the side of the carby cylinder but it came off easily enough with the cleaner. The jet looked fine as far as I can tell. I left it where it was - rather than reset - since I'll be checking the timing again and then get on to the ratio when the PCV comes - (winding its way across US right now.) How do you manage for bits in Europe?
South Australia is a bit of an old cars graveyard (no MOT here and little or no rust) but these cars are pretty old (hey 49 is not old...)
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Post by paddymk2 on Jan 26, 2018 8:10:41 GMT
One other thing, when I got the car there was a piece of metal literally wedged in between the engine and the brake booster. I pulled it out and set aside - cause it didn't look very OEM. But I'm thinking it is a rather makeshift heat shield to protect the fuel input side of the carby - and that someone's had a go round with this issue before. BTW When I took the car to the registration check - the bloke there said he had had one and it often suffered from vapour lock. (I'd managed to get to the test centre but when I stopped and tried driving into the inspection centre it wouldn't start - started ok when cool.) Wondering is is worth putting back - part of its heritage? Or is there a better type of heat shield - (forecast is 42oC for Sat and Sun) Paddy  |
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Post by dave1800 on Jan 26, 2018 11:11:56 GMT
Hi Paddy There have been some reports of vapour lock caused by heat soak when a hot car is parked for ten minutes or so, but it isn't a universal issue. The first thing to do is try and confirm it is vapour lock. The easiest way is to open the bonnet and see if that speeds up the restarting time. Next confirm the fuel delivery. If you have an electric fuel pump pull off the pipe at the carb and turn on the ignition, catch the fuel in a container well away from the exhaust! If the pump is mechanical then you need to turn the engine on the starter. One solution that apparently works for some cars is to pull the choke in and out to release any trapped vapour bubbles in small diameter nylon pipe leading from the float chamber to the jet. The pipe and float chamber need to be perfectly clean as any grime can make this worse. Check the routing of the fuel pipes to keep them as far away from the exhaust manifold as possible, although I believe the problem is most likely caused by the fuel boiling in the float chamber and that would be where I suggest some form of insulator is applied initially. There were some made for MGBs that could be adapted neatly and probably from local Australian carb cars too. SU make insulating spacers (I'm not sure whether the Oz spacers were this type of aluminium)that may help SU parts With a bit of ingenuity a small 12v computer fan could probably be fitted with a timer and thermostat to keep things cool when the engine is turned off if the problem persists. Unless you have an aircon, I think 42C calls for a cool beer and not sweltering in a crab! David Wondering is is worth putting back - part of its heritage? Or is there a better type of heat shield - (forecast is 42oC for Sat and Sun) Paddy Attachment Deleted[/quote] |
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Post by dave1800 on Jan 27, 2018 1:24:58 GMT
Just found this article on the Hindustan Ambassador in India that used a B series engine with a similar combined inlet and exhaust manifold. It suggests the problem was the fuel pump getting hot and the "cure" was a wet rag. Don't know if this is true or anecdotal. But in theory the fuel pump shouldn't account for a hot car failing to start after parking as the float chamber should still be full. Still a good read. David India |
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