1970 Austin 1800 MkII.

Don't panic!

It can all be resolved by applying logic and one thing at a time and in this order.

My suggestion which concurs with the Moss videos linked below can be summarised as:

1.Check the TDC pointer and crankshaft pulley marker are correct by observing the piston movement (Moss video 2). Re-mark if necessary.
2. Check the camshaft timing specs , eg 5,45,40,10 using the timing disc
3. Set the camshaft timing (Moss video 3), determine the camshaft profile
4. Reset the valve clearances in light of the camshaft fitted ie probably 0.015" or 0.018”
5. Set the ignition timing to w/s manual spec
6. Tune the carb
7. Re-measure the vacuum and compression.
8. Have a beer

The first thing to do is to sort out the timing marks. There are some very clear Youtube videos posted by Moss that are well worth watching (especially the 2nd and 3rd which show you what to do).

Moss 1
Moss 2
Moss 3

Observations
There is clearly something fundamentally wrong. You noted that when the engine was set to TDC that the crankshaft pulley timing mark was around 20 degrees after TDC. My question is how was TDC determined?

If using the dial gauge and using No1 valve opening as the indicator this would not be accurate as it would include any errors in the valve train. You would also need to make an assumption about the camshaft profile.

I would suggest if you have not already checked TDC by a method similar to Moss that this is your priority as all other settings stem from this.
 
The photo showing the old timing chain does show some misalignment. While it is difficult to determine from the angle you had to shoot the photo it looks to be less than one tooth which is 18 crankshaft degrees, but again without the tensioner I cannot be certain.
 
Errors can occur if the rubber between the inner and outer sections of the crankshaft pulley distorts making the timing mark wrong but 20 degrees seems excessive unless there are very obvious signs. The later crab pulleys had a revised mark when the pointers were moved to the top of the timing cover but the difference was of course far greater than the 20 degrees so that can be discounted.

There were two or three different tensioners for MGBs, the problem could be Moss’ fault or you may have a different back plate.

A Tommy says when it comes to setting the camshaft timing you need to open the tappets to 0.020". Of course you may not be 100% certain what camshaft is fitted to your engine so the first task is to take readings. The standard Mk11 cam was 5,45,40,10 and the MGB / 1800S, 16,56,51,21.

As you know a steady low manifold vacuum can result from an air leak, retarded ignition timing or late valve timing. Given your compression reading is even and now more reasonable other factors can be reasonably discounted. As a matter of interest where have you taken the feed for the vacuum gauge?

However, you noted pinking in every gear under load which would occur if the ignition timing was over advanced. This questions in my mind whether the initial observation about the crankshaft pulley marking being off by 20 degrees is in fact correct? The fact that you experienced good low down power could also indicate an over advanced ignition timing – but conflicts with the vacuum gauge. Has the vacuum gauge been checked against a known good engine?

Remember the vacuum gauge help


David

It is highly unlikely that many of the vacuum advance mechanisms are still within spec as the diaphragms and springs age.

You can set up a test rig fairly simply by attaching the mechanism to a hypodermic syringe and T-ing in a vacuum gauge and checking the advance with a timing light. (Plug the carb take off to avoid an air leak). You can then see if the unit you have is operating reasonably close to the original. As your cylinder head has been skimmed in theory raising the compression it possibly needs slightly less vacuum advance.

The vacuum advance mechanism used on Mk11 distributor 41234 shows 5 degrees advance starting at 1" Hg and ending at 12 degrees at 7" Hg (crankshaft degrees and fairly linear between these two points.

The most important factors from the engine safety perspective is that the advance returns smoothly and quickly to zero under wide open throttle and anywhere from around half open throttle or slightly less without sticking. Driving without the vacuum advance operating will cause hesitation off idle, poor drivability under light loads and higher fuel consumption but won't damage the engine. Over advancing ignition timing is the killer. If the vacuum advance diaphragm is punctured it will not perform properly and be a source of an air leak affecting the mixture. Remember the crabs used ported vacuum take offs so there won't be any vacuum advance at idle.

David

However, I should have tried starting her yesterday. Would she go this mornng? Would she 'eck as like. No spark. Proved to be the condenser, as when replaced she fired up straight away.

Further to comments concerning the vacuum advance, I have managed to source a refurbished 41415. This is a 45D, rather than a 41234 25D, but the two interchange. Hopefully it will sort out some of these problems.

Chris.

So much repro Lucas stuff is just junk these days.

The starting problem didn't entirely go away. The car was driven for five hours on Wednesday, so you would think that it would be brimming with electrical goodness. Engine chugged over slowly this morning. A quick check showed 11.54vDC. Dropped the spare battery in and "Whizz!" - away she went first turn of the key.

Chris.

Things are plodding along. The car is running quite nicely. I did acquire a factory refurbished 45D 41415 distributor, which was fitted two weeks back. Ron sort of sniffed at it, took it to pieces, cleaned and oiled everything and fitted the genuine (red) Lucas points and condenser and a Distributor Doctor red rotor arm which I had aquired separately. When fitted, we tinkered with the timing a bit and the result is better. Much better. Starts first time, doesn't run on as much and the fuel consumption has improved. The car is running very nicely. However, the vacuum gauge is still only showing 12.

Austin 1800 by Penguin 45, on Flickr

Tweaking in progress. Ron approves.

Austin 1800 by Penguin 45, on Flickr

And a few days later.

Not sure what to do about this. I could obsess about the low vacuum reading, but the car is running nicely with adequate power, so leaving things alone is a tempting option. However, I have assembled a kit of Mobelec parts over the past three months which would allow the car to run a positive earth electronic ignition system, which interests me greatly as it's all period stuff.

Reading the WM shows that 150psi compression is about right for an LC engine, and that lower vacuum gauge readings should be expected. That's fine, but the car has flat top pistons and the head has had a .009" skim, so should be a high(er) compression engine.

Bah, humbug. The MoT is due in a few weeks, so there are other things to deal with.

Chris.

A little reminder that it's always worth putting information up in forums, as sometimes it is picked up on. Mark, the PO of the car, has been in touch to say that the camshaft was changed when the engine was rebuilt some years ago. Now we've got something to go on.

Chris.