Temperature: Above Normal or Just Average?

Thanks for that info
The engine cut out with the bonnet open.
I'd only noticed it really cutting out with the bonnet open and fiddling around the engine.
but previously I noticed it very difficult to restart when hot.

When you say set the timing correctly, did you mean just set the static timing? (And leave the vacuum timing method?  I thought that was kind of neat, and thr vacuum seemed to pull a lot more.  Still need to check but I think I've turned the distributor about 10 more degrees anticlockwise so it should be more advanced.)



Regarding setting the mixture, its a wee bit difficult if the engine stumbles while warming up.    So my starting point was 2 full turn down from the jet all the way up to the piston shoulder.  I had look at the spark plugs last night - they're black and sooty (not right) but they don't appear as if its running lean (although starting it up in the garage is different than a proper run.)

Yes the vacuum gauge has a low pressure side. And yes I should fit a filter.  And have another look inside the float valve etc.

Its possible things have been moved around the fuel lines - how far away are they supposed to be clear from the exhaust manifold? (looks to be  about 2-3 inches.)  I didn't notice the phenolic block on the pump - waiting for the daylight on Sat to see...

The heat shield is very make-shift , literally a thick sheet of aluminium (0.2mm) folded to cover the fuel pump fuel lines, float and pressure regulator - but letting some air flow around.  I plan to check its effectiveness with a thermocouple and implement if its helping.

Thanks again
Paddy
 

Good stuff from Tommy. Both my cars use electric pumps back by the tank. I have had no joy with the mechanical ones over the years. It means that I can run the fuel line up under the master cylinders, across the back of the displacer tube and loop back from under the servo. The fuel line is never closer than six inches to the exhaust at any point. I don't have any fuelling problems - mine ar all ignition related.

Chris.

Yes, thanks Tommy I agree everything is pointing to a fuelling issue, too much or too little.

The electric fuel pump mounted at the rear not only runs cool but pushes fuel instead of sucking the length of the car which is a great advantage if there are vapour bubbles in the line as they are compresed.

Paddy, the ignition timing should be set initially at the static setting. This is slightly different from the UK spec being 10 degrees not 9 (but a not critical difference). Mk11 Oz cars had slightly lower CR 8.8:1 vs 9.0:1.

You can also check that the mechanical advance works by using a timing light with the vacuum advance pipe disconnected and plugged to avoid air leak into the carb. You should also check the vacuum advance works by sucking on the pipe to make sure the diaphragm has not split and watch the distributor plate moving smoothly. If it doesn't work the engine will be retarded under light to medium load and the exhaust manifold run hotter and if the diaphragm is split it will leak air and upset the mixture setting.

Tony Cripps published a series of excellent Newsletters that are on the Oz site I linked earlier. He noted in Newsletter No 3 that there were errors in some of the Oz workshop manuals regarding the distributors and confusion between distributor degrees and crankshaft degrees which may have resulted in some cars being wrongly timed. Well worth a read, the correct figures are presented in the technical service bulletins.

The correct info for testing with the timing light for an Oz Mk11 care is:


Distributor = 629410797B (stamped on side plate) part no AYH 0576 Type 29D (UK = 25D)
Engine RPM / Advance

  700 rpm   11 deg
1200 rpm   14 deg
2000 rpm   21 deg
2600 rpm   26 deg
3800 rpm   30 deg
5000 rpm   34 deg
5600 rpm   34 deg

NOTE: These figures include the static advance of 10 degrees BTDC. (I wouldn't advise checking beyond 2,600rpm with no load on the engine ie on a dyno.)

Vacuum adv 11 degrees @ 15" Hg


David

It looks as though you may have an ignition timing and a fuelling problem. The latter is probably where to start.

Fuelling

The black smoke may have been an indicator that the float valve isn't seating and causing the engine to flood rather than incorrect jet adjustment.

If this is the case, by weakening the mixture you may have caused the temperature to creep up by creating a situation where the engine was running weak and intermittently flooding. If you take off the float chamber lid, turn it so the float is uppermost and blow into the fuel inlet pipe you can check if it is sealing and / or sticking. The w/s manual shows how to check the correct height using a 3/16" (5 mm) drill bit as a spacer between the float and lid - you or may not have an adjustable float. If the float has any fuel inside it then it must be replaced as it will flood if the float is punctured (modern fuels can damage the floats and Burlen make unsinkable floats now.)It's easy to dismantle and check the valve and check it is not worn and is seating properly and is thoroughly clean.

Ignition

There's something very odd with your ignition timing results when changing the idle from 700 to 800 rpm you should only have seen an increase of about 1.5 degrees of advance not 4-5 which I do not understand - it could be a weak spring in the distributor or jitter /slack in the timing gear drive train. Does the timing light give a clear steady indication or does it jump around? What you will need to determine is whether the timing marks on the pulley are accurate and the maximum ignition advance doesn't exceed 27-28 degrees at 3000 rpm - I wouldn't suggest going to 34 degrees at 5000 rpm lying under the car. As you know exceeding the max advance at high rpm and load is THE engine killer.

Vacuum
As you earlier noted a higher and more reasonable vacuum with more ignition advance I suspect there could be an issue with the timing mark on the pulley - I assume the pulley is tight on the crankshaft and the Woodruff (locating) keys are intact -can you feel any play by rotating the pulley? The other consideration is whether the valve timing is correct as this can lead to low vacuum.


At this stage I think it better to be 100% with the fuelling/valve clearances/air leak checks and not be tempted to advance the ignition to regain vacuum.

We discussed how to check the accuracy of the timing marks in Tommy's thread and more recently in Chris' and the valve timing can be checked at the same time but at this stage can you look at the crankshaft pulley to see if there is any movement on the crank and if the rubber between the inner and outer sections is secure / distorted.

Finally, double check your readings and if possible check your timing light and vacuum gauge against a known good source if you can.


David

Pulled of the wheel to make it faster to have a look
The car started easily - perhaps fast, not sure if opening and blowing through float valve may have done something?
Waited till it warmed up 
Idle was 700-800 rpm
Checked advance degrees
800 about 12
1000 about 14
2000 about 20 
                         

That looks about right.

Still a bit of smoke at the tail pipe and the temp at top of N.

Will put it back together and go for short run.

Best regards
Paddy

The Oz cars do in fact have a lower idle but I would suggest keeping it at around 700 at least until this problem is resolved (it will be!)

David

Hi Paddy

That's really encouraging. I'm having a think about what could possibly cause the vacuum to increase from 5 to 15" Hg as it warmed up. It should stay reasonably constant. I guess the first thing is to try and get a really good vacuum gauge connection.

I would have thought that the radiator being re-cored should have removed any leak stop from the equation. These engines set up properly have bags of low down torque and will climb mountains as Tommy can vouch.

Anyone have thoughts about why the manifold vacuum should increase as the engine warms up? (I assume you didn't have the choke on which partly opens the throttle for the fast idle?)

David