New vacuum advance unit, no difference

[gatsby989]

I have a Weber DGV carb.
I tested my vacuum advance unit a while ago, and no amount of sucking could get the thing to move. So I bought a new one and a new vacuum hose too. Swapped it out yesterday. Sucking on the hose now causes it to move the plate in the distributor. Hooked it up to the carb, however, I don't notice any difference at all in how the car runs. Could it be that the Weber doesn't create enough vacuum to operate the advance? Could there be a vacuum leak somewhere else? Any tips on checking for such leaks?

I fiddled with the timing a bit since I wasn't noticing any difference. I advanced it with the intent of trying to get it to pink slightly going up a hill. I never heard anything like pinking, but the engine felt really slow and powerless, so I retarded the timing again, a little more than it had been. The engine definitely pulls better than when it was advanced, but overall, I don't notice any difference in how it runs. I'm guessing it was over-advanced to compensate for the knackered vac unit?

The "problem" I'm having is that when the car is cold, it will start and idle fine with the choke. However, unless you let it sit there and warm up for at least 5 minutes (or longer, depending on the temp), it won't drive well because there's too much choke... but push in the choke too much and it dies. Once it gets warm, it's fine. I'm relatively young and this is my first "non-modern" car. Is this a "problem" or just the way it is?

This occurs even in summer, when it's 100F, but of course is much worse in winter. Average temp when I go to work in the morning in the winter is between 20-30 deg F. Sometimes a bit less. The Morris dutifully starts, but definitely doesn't want to go anywhere without idling for a good 10 minutes or longer at such temps.

What do you guys think?

[mike.perry]

If you are new to Morris Minors I would suggest ditching the Weber carb and fitting an SU. They are easy to set up and have known characteristics. When you have the car running correctly you will have something to compare the Weber with.

[Alec]

Hello Gatsby,

that is the problem with fitting a different carburettor. When the manufacturer sets up an engine the carburettor and the ignition are optimised together. The reason for the vacuum advance is to enable the car to run correctly with the carburettor set weak at cruising speed to improve economy. In other words the vacuum advance is part of an economy device together with the way the carburettor is set up.
The simple S.U. is a much better carburettor than people seem to think.
Alec

[liammonty]

Hi,
I totally agree with Alec and Mike. Unless you've 'set up' the carb since it's been on the Minor, the chances are that the jetting is completely wrong, as they were never jetted as standard for the Minor. I would think, given the problems you're having, that this is the problem. The effect of having a non-functional vacuum advance would likely be a hesitation accelerating off idle, and a slight loss of MPG, but not much more serious than that. If you want to stick with the Weber, you will need a rolling road session, and you have got double the normal amount of jets to mess around with, as I believe it's a twin choke (had one on my T2 VW a few years ago). You've got emulsion tubes, idle jets and main jets, air corrector jets, accelerator pump exhaust jets and idle jets all to take a look at- it gets tricky to do it without the help of a rolling road. At a push, I think there might be a guide in the Vizard book to setting these up, but I'm not certain.

Like Alec said, your best bet, unless the engine is seriously modified, would be to bolt on a standard SU (cheap to buy second-hand) and you'll find it will run very nicely. Good luck with it.

[bmcecosse]

A 948 engine doesn't need any larger carb than the manufacturer provide. You are experiencing all the problems of a non standard carb. Fit an SU HS2 and enjoy the car.

[gatsby989]

So is the too much /not enough choke / long warm up time not an issue with SUs? Besides that problem, the car seems to run pretty well. It was running rich, but swapping out the idle jet seemed to take care of that. Although it might still be better with smaller main jets too.

It has exhaust headers on it, but I don't know if it's otherwise been modified. I've yet to take the head off.

[liammonty]

With a well-adjusted SU (very easy to set up, as there are only 3 adjustments- mixture, fast idle and idle), they are extremely driveable from cold. You should be able to start up and drive off immediately, with no trouble, almost regardless of the temperature. 3 yrs ago I was rattling around in mine in the snow at around -10 degrees C (around 10 F?), and the Minor started and ran as well as my modern car. SU's really are good, and much less 'fiddly' than Webers etc.

[IslipMinor]

I tend to agree about the DGV, but before rushing off and putting on a standard single 1 1/4" SU, it would be worth finding out more about the engine spec. It seems a bit odd than someone would fit a DGV for no good reason, so it might need a bit more than a single 1 1/4"!

Is it a 948 for certain? Do you have a picture of the block on the exhaust manifold side towards the front of the engine - is there a 950 or 1100 plate there? Does it have removable tappet chest covers? If not, it is a 1275 block!

What is the part number cast into the head - you can see it after removing the rocker cover.

[gatsby989]

Thanks all for the feedback. I'd knew you'd tell me to ditch the Weber. I think I'd have to redo the exhaust if I do that. The current exhaust is a lcb... would going back to the standard exhaust cause decrease in performance?

I am certain it's a 948. There's a "950" cast into the block. The head looks like it says "CAM 4910" and "27 K 9." I've also got a 2A629 head in the box o' random stuff from the previous owner.

Here's something I pulled out of the box. Is this a HS2 carb? The only numbers on it I can find are what look like "AUD 3255" which is marked on there using dots, like it was done by hand. It's not cast.





It's obviously missing the air cleaner. And I'm sure would need a rebuild.

[chesney]

Certainly not an HS2! Isn't that an HIF?

[IslipMinor]

Not an HIF series, the carb in the picture has an external float chamber, but could be an HS4? To check, remove the carb from the manifold and measure the diameter of the carburettor bore where it bolts on to the manifold. It could be what was commonly called the 'Mini Automatic' manifold?

Then the choice is either to find a separate 1 1/2" inlet manifold to go with the the headers (what type are they?), or use the complete inlet/exhaust manifold, which would mean changing at least the front of the exhaust system to match. Do you have a picture of the exhaust side of the engine as it is now?

[bmcecosse]

It is an HS4 - keep the lcb - either find an alloy inlet manifold (MG Metro etc) or cut the inlet off that exhaust - and use it. The head is a standard valve size unleaded from a Mini 998 - no performance advantage I'm afraid. The carb is a wee bit on the large side for a standard engine - but it will be fine !

[gatsby989]

With a well-adjusted SU (very easy to set up, as there are only 3 adjustments- mixture, fast idle and idle), they are extremely driveable from cold. You should be able to start up and drive off immediately, with no trouble, almost regardless of the temperature. 3 yrs ago I was rattling around in mine in the snow at around -10 degrees C (around 10 F?), and the Minor started and ran as well as my modern car. SU's really are good, and much less 'fiddly' than Webers etc.

That would really be great, not having to sit around and wait for it to warm up. Although 25*F or so is probably average, it can be quite a bit colder than that. I realize some warm up in the winter is probably necessary, but it seems excessive now, especially in the summer.

IM: I measured the carb and it looks like it's 1.5" where it joins the manifold. The exhaust was built by a local guy. In one of the pics below, you can see that the center exhaust is actually rather mashed when they put the weber on.





Look what else I pulled out of the box. This one is smaller. There's an exhaust manifold that goes with it too. This one has the numbers "AUC 6070" cast into it.




So... hunt is on for a new manifold I guess? Do you suppose that center exhaust could be fixed relatively inexpensively?

[MarkyB]

That should work OK with your existing 3 branch manifold.
will it need a plate to cover the hot spot area?

[izzi]

Hi,
Is the engine original, or has a modified 5 bearing crankshaft engine type been fitted.
If so you could be on a different game altogether.

If it is the original engine then you have been given good advice.

Roy

[bmcecosse]

5 bearing crankshaft A series - now there's a new one on me !!!
The smaller carb is an H2 and that's the early (not very good) inlet manifold - you could use it at a pinch meantime - but indeed you may need to bolt a plate across the 'hot spot' if it's open. The damaged exhaust is in the worst possible place of course - the shared port centre branch. Probably need to cut away the damaged surface - and weld in a new piece of steel. but actually - for a standard 948 engine, the LCB is an overkill and may be losing a little bit of power. However - I would certainly keep it meantime, while searching for a decent head to put on the engine, and then it will come into it's own -along with the larger HS4 carb.

[izzi]

Hi,
I should have entered Type B engine, although doubtful,

Roy

[bmcecosse]

Indeed the B series did eventually go 5 main bearing - but this is v definitely an A series.

[gatsby989]

Thanks guys for all the info. So I should try to hunt up one of these mythical 12g940 heads? I'm afraid finding one here in the states will be difficult / expensive since the morris is a rarer bird here. Just saw what they ask for new / remanufactured head. This might go nowhere real fast...

[bmcecosse]

Look for an Austin America as a source of the head.....