Temperature: Above Normal or Just Average?

What I meant was that if you checked the vacuum when the engine was cold - if you had the choke out when you found 5" Hg - the choke mechanism also opens the carb throttle butterfly so that lowers the manifold vacuum.
If the choke was in and the vacuum rose as the engine heated up that suggests a vacuum leak between two surfaces that seals as they expand with heat - manifold gasket maybe.

As far as the weeping core-plugs go I suspect this just prevents the water pressure from holding up when you turn off the engine. You can test this by letting the engine reach normal running temperature, turn off and check for residual pressure after say 15 minutes by releasing the pressure cap - slowly and carefully! If there's very little or no pressure then the leak may be slightly affecting temperature - I've seen about 3mm movement on the temp gauge with a slight pressure leak. Sometimes these things can weep just while the block heats or cools. Best keep an eye on them and the water level, it's not too hard to replace those on the front of the engine but the one at the rear is a problem. Is the weeping from around the edge of the plugs or are there pin holes in them?

David

That's the core plug that the MG guys complain leaks first - you're getting there definitely not the end of the world!

David

Thanks Chris - I'll see if I can see anything written on the pump.  Cheers Paddy

The only thing I could see was this
 
- same location as the MOWOG name on the original part.

Its really hard to read that but it says something like GOVNTY

Thanks for the comment Dave I'll get the dimensions of the pulley...

I will get back to you asap to confirm whether you have the correct fan pulley. I would advise trying to get to the bottom of the problem by getting the basics right before experimenting with other fans. Some of the Mini fans for example were designed to reduce noise but were less effective and as you say the MGB pulled the air as well as being designed for different spacing.

regards

David

Ok, so we're eliminating potential component issues.

As you noticed the vacuum improve as the engine heated up this is strong evidence there is a leak between two mating surfaces. Can you double check for an air leak; that would definitely cause the mixture to run weak at idle and lead to overheating. There are only a few areas to check:

manifold to cylinder head gasket - gasket Ok, bolts tight
carb to manifold gasket - ensure all mating surfaces are clean and flat, undistorted and bolts tight
brake vacuum take off from manifold,
PCV pipe take off from manifold
carb throttle spindle wear (temporary seal end of throttle shaft with petroleum jelly
vacuum advance pipe to distributor


When you remove the oil filler cap with the engine at running temp how much does the idle speed increase? If less that around 150 rpm or if it hestitates the mixture is too weak, make sure the carb resvoir is topped up with oil.


If you are certain all this is OK then re-check the manifold vacuum and advance the timing by rotating the distributor until the gauge reads 18-20" and note the stroboscopic advance, then return it to its current timing setting. This will indicate if there may be an issue with valve timing or ignition timing mark error.

David

Hi Dave,
I checked for leaks around the manifold. 
I inspected the joints, tried to hear any hissing, and then gave a dust of carby cleaner (Engine pretty cold and fix extinguisher ready)
    carb throttle spindle wear (temporary seal end of throttle shaft with petroleum jelly

        vacuum advance pipe to distributor
- I wasn't really sure what and how much so I'll need to do that again.


I checked the boost in RPM by removing the cap.  It went from about 700-740 to about 880-900.  Also there still a bit of black smoke puffing out the tail pipe.
Its a bit cooler today - it took longer but the temp still crept up to above normal.

Ill pull off the grill and wheel and set up for the stroboscope 

Paddy