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MG Midget and Sprite Technical - No vacuum advance on the distributor

Hi everyone

This is my first post. I have just bought a rubber bumper 1500 midget that needs some work to get it running.

I serviced the distributor, ht leads, plugs last night and noticed there is no vacuum advance fitted. It looks like there is a blanking plate in place instead.

This isn't normal according to my research. Why would someone have set the distributor up like this?

Chris
C MADGE

It is probably a "sports" version without vac advance - not factory but fitted by a PO - there may be other mods to the engine. More research needed!
Chris at Octarine Services

It could be that the engine has been modified and a different distributor fitted to match.

Equally, it could just be that the original distributor had a problem and has just been replaced with whatever was to hand.

Does it have after-market electronic ignition fitted, by any chance?
Dave O'Neill 2

No its the mechanical points with condenser setup.

The engine is gold in colour. Is it right to assume this is a Gold Seal factory reconditioned engine or did they come in gold colour as new too?

C MADGE

Hi Chris, welcome,
it's best not to assume anything with old cars especially if it's fairly new to you, the engine might just have been painted gold. If it's a Gold Seal engine then it will have a certain engine number to it, so what's the engine number, approximately if you don't want to give full details.

A good quality photo of the area posted here can often help and keen eyes spot other things.

Great that you're researching, here is a very good source but at lot of internet stuff is inaccurate. There are good books you can get, the best for new owners is the relevant Drivers Handbook.

Note, there were many changes and differences to the 1500 over its production even though they look the same. Many parts and components are compatible backwards and forwards but not all. Also there can be lots of modifications to the cars over their life so often more details are required otherwise assumptions are made and they could be wrong.

If you've not already got a copy then this is the first book you want as a new owner - (Ref. 0058) - http://www.mgocshop.co.uk/catalog/Online_Catalogue_Handbooks_5.html

There are other good paper printed (or electronic versions) books available depending on what you want or need, Haynes are popular but can have errors and omissions and not be entirely relevant to existing cars so they need back up from other sources.

The Archive here can be very useful but can take a time to find what you want especially if you get distracted by all the info and interchanges there.
Nigel Atkins

Thanks Nigel, that sounds like some great advice. I have put the hand book on my christmas wish list ;)

It is all very new, and there's a bit of a learning curve to go through, so excuse the numpty questions.

I have been googling the engine number but nothing matches up, and then I discovered I have the casting number not the engine number..........

As I say, lots to learn!
C MADGE

Yeah, sounds unusual. I have never heard a good argument for not having a vacuum advance, so my humble recommendation would be to look into getting one, although finding an appropriate one can be tricky. It will help with general smooth running and improve your economy.

What is the dizzy part number? This is stamped on the body and is five numbers, usually starting with a 4 (i.e. 4xxxx).

Engine number is on the top block face on a little plinth jutting out at the back, distributor side of the engine.

Malc.

Also: welcome!
Malcolm Le Chevalier

Vague recollection that on some 1500's the vacuum "advance" was set up to in fact retard the ignition, to combat pinking as they tried to get them to run on an excessively weak mixture for economy. Maybe combined with the use of those silley poppet valves in the carb butterflies.
GuyW

Chris,
if you can you want to get the Driver's Handbook before Xmas as its contents could perhaps say you time and hassle and incorrect info or assumptions.

Don't just rely on Google as it's not as good as it used to be and it wasn't always that reliable anyway.

If you want some very basic, non-technical, non-mechanical, notes that you'll probably find OTT, non-sexy and probably not appreciate until you've got more experience and/or got rid of the car, just email me, they were originally drawn up to help a young, newbie MG BGT owner a few years ago but have been adapted to cover generally the Midget 1500.

my first and last name at bt internet dot com (all lower case)
Nigel Atkins

You can pick up a free printed parts catalogue from Moss in Bristol (just off the end of M32) which is a very useful reference.
I thought all the 1500's had vac advance as standard.

Moss list a dissy without vac in the 'performance' section - noted as for use with Webber carbs.

Where in Bristol are you - I'm down in Clevedon.

R.
richard b

Chris,
parts lists and drawings are very useful but be aware that they along with Haynes and even factory publications aren't always 100% accurate. Always cross reference any info you get (from any source including me) with, if possible two, other reliable sources.

If you get, read and refer to the relevant Driver's Handbook then you will know more about the car than many, even long term, owners.

Here's just one example of something in the Driver's Handbook that can save confusion for newbies and some, even long term, owners, how to use the heater system and the fresh air valve.

From my experience of daily Spridget use over many winters I keep the fresh air shut-off valve fully open (unless preventing heavy traffic fumes getting in cabin) to get the most heat to the windscreen or cabin and fresh air when warmer, I keep mine fully open or vary rarely fully closed, nothing in between.


Nigel Atkins

The engine number is:FM38556HE
I’m waiting for the V5 in the post, but I believe it’s a 1975 according to the MOT history. However the engine number does seem to match up to that year unless i’m missing some thing?

Richard i’m In Thornbury, just north of Bristol.

Nigel I have emailed you, thanks for the offer of the info :)
C MADGE

The distributor is a Lucas, with 3389 stamped on the side.

C MADGE

3389 I believe that is the date code.
week 33 of 1989. So if your car is a '75 this is a later modification
GuyW

I'm going to make an assumption ... HAHA

sorry Nigel

It's actually a good guess and a decent possiablity

IN the USA the 1500 only came in a (primitive) electronic ignition system and it had a flaw it had some kind of fusiable link that would go bad in the drop of a hat and had almost no work around ... this is my understanding...im not a 1500 person

The Lucas dissy for the 1275 and 1500 where interchangeable with some exceptions as Nigel pointed out

around 1970/71 Lucas had a dissy for the 1275 that did NOT have a vacume advance it was rare and I think it may have only been used on the A+ series engine (mini) and it was points and condenser based
not electronic

It's possible that you could have gotten one of those dissys as a replacement sissy


Putting a sissy from one engine into the hole of another engine provided it fits is very simple and anyone can do it




The problem is this type of modification is not easy and actually outside the grasph of most people as it's very complex well before the actual easy wrench turning takes place. If this is something not done with presion it can have disastrous results

What you need to be aware of is what is called dissy curve... it's the science that determine when how and were the spark will occurs inside the combustion chamber and each population of engine has a different dissy curve separated by manufacturing year to basic modifmodification to things like air filters and carberation settings amoung many other conditions

You can have a dissy recurved to fit your engine there are specialty shops that can do this

Or you can do an aftermarket dissy and have limmited success based on the quality of the product and your personal ability if you know very much about the art of recurring a dissy if your not then

And your close to kent... look up Peter Burgess he has a supplier for 1-2-3 dissys they can be set up with a lap top computer or a more hands on approach ... Peter has the shop and rolling road to do it properly and the experisnce of age on his 100 year old bones to set it up correctly and get everything out of it that can be had...he is worth dropping a dime and having a chat with

I would not fluff over this, having the wrong dissy with an incorrect curve can become casistropic for an engine and become very expensive. Esp. If you dont know the black art and science of distubtors

Prop


1 Paper

The vac. retard was for American cars. All UK had vac. advance as far as I was aware.

The standard dizzy should be part no. 41449. It might be that the vac. can has just been removed? What has been done at the carb./manifold end of things?!

Seems like your engine has been transplanted from a Spitfire at some point in the past also.

http://www.triumphspitfire.com/enginenumbers.html

Exactly the same engine though, so wouldn't worry about it if it is running OK.

On the bright side, at least it has a good rotor arm in it! :-)

Cheers,
Malc.

Edit: Also... don't get me started on the "Webers shouldn't use vac. advance" performance distributor nonsense :-D

Malcolm Le Chevalier

The dissy in the photo is a 43D, so not from a 1275.

The 1275s without vac advance were fitted with a 23D, and were from 1966/7.
Dave O'Neill 2

Chris,
it might pay you, or at least be interesting, to pay £5 and get the car's recorded DVLA history by filling in form V888, just put the truth, it's a "Historic" vehicle and you're interested in its history. - https://www.gov.uk/government/uploads/system/uploads/attachment_data/file/644983/v888-request-by-an-individual-for-information-about-a-vehicle.pdf
Nigel Atkins

Thanks Dave.

Now all I have to do is retain that info until I need it ... which should be around ... 7 more years, so shouldn't be priblem haha...

Prop
1 Paper

Thanks for the replies.

I'll have a look at the carb tonight, fairly sure its not a Weber though.


The engine number is stamped into a flange by the no. 4 cylinder. IE the original engine number.

So the engine was originally out of a Spitfire but it is gold in colour. I guess it could have been repainted in gold to maybe look like a reconditioned engine.

Or could the gold seal engine plate have been lost ? If so is there a resource to match the gold seal reconditioned engine to the original number ?

In the grand scheme of things it doesnt really make much difference, the car has 95,000 recorded miles on the clock, but I'm curious to know a bit more of the history of the car.



C MADGE

Tear it all apart and see what's inside! :-D
Malcolm Le Chevalier

Chris,
as well as the £5 DVLA history you could pay (a lot) more and get a Heritage certificate but bear in mind most Spridgets will have many variations from how they left the factory 40+ years ago.

https://www.britishmotormuseum.co.uk/archive/heritage-certificates

Also Terry Horler's book can give you lots of info plus if you put up your approximate chassis number you can get a lot of info here and elsewhere on t'net.

Original Sprite & Midget The Restorer’s Guide by Terry Horler –
http://www.amazon.co.uk/gp/product/1906133336

ETA: There could be info on matching Gold (and Silver) Seal engines in the Archives here.
Nigel Atkins

hi
As previously mentioned 'weber Carb. Even if you dont have one fitted now, a previous custodian may have had one and so fitted the distributor you have. The non vacuum dissy imo is a must for the weber..Well that is what i told the wife when i paid out for a new one !!!
rgds tony
tony boyle

Does your distributor have a mechanical advance setup? Just curious, as I run a Mallory distributor in my 1500 that uses mechanical advance and no vacuum fitting of any kind. Works just fine...

-:G:-
Gryf Ketcherside

The reason for removing the vac advance, especially on a tuned engine, is to ensure there is no floating of ignition timing due to movement allowed by the vac advance. Sometimes folk screw the baseplate so the vac advance cannot alter the timing.
Peter
Peter Burgess Tuning

Yes the advance is the mechanical system within the distributor.
The engine has the standard SU carbs and standard exhaust so it hasn’t been tuned from stock recently.

This might be a good excuse to go with electronic ignition :)
C MADGE

Bear in mind what Chris said at the top. Maybe the po had a problem with pinking caused by vac advance so fitted a non vac dizy? Maybe the po did some sprint and hillclimb in std class and went down non vac route. Don't rush changing dizzy, maybe get it on a rolling road to see how it runs?
Peter
Peter Burgess Tuning

Dump the points and go electric. Hours of fun to be had refining timing and trying new curves....
Oggers

Yeah, on a racer, where you are WOT the whole time. The vac. advance serves no purpose, so ditch it. On a road car, I can't see why you wouldn't want one.

It still doesn't really explain things. Did you find the dizzy number? As this will (in theory) give you the advance curve. Or alternatively, look inside the dizzy and see what numbers are stamped on the bob weights. This will at least tell you what your max. advance should be.

Cheers,
Malc.
Malcolm Le Chevalier

I’ll be setting the timing in the next few days, so I can have a proper look at the distributor and get an ID.

Thanks for the responses so far
C MADGE

It would be interesting to see mpg differences with long term testing with and without vac. Might need a 123 system so the vac disconnected does not upset baseplate and subsequently the mechanical advance on a mechanical distributor.
Peter
Peter Burgess Tuning

...or maybe he was just a victim of advertising and fitted a "sports" distributor because they thought it would be better ...

I have seen many cars fitted with parts that were supposed to be better / faster / more economical / etc which actually resulted in poorer performance / economy.
Chris at Octarine Services

The distributor has a number 8 stamped on the weight mechanism, so if I understand correctly that’s 16 degrees max advance at the distributor plus the static? See pic.

With the timing light at 750 rpm advance is 6 degrees, so add the 16 and that’s only 22 degrees maximum.

The timing light at 3000rpm showed 16 degrees BTDC. Unfortunately I ran out of time to take any further readings up the rpm range.

One of the springs is corroded and slack so isn’t actually doing anything. I’ll replace this distributor with an electronic one before I get the car on the road which at the moment feels like a long way off.

Nothing on this car is standard it seems, and there’s a few bodges to sort out.



C MADGE

Installing one new spring seems a bodge and is it even the right one, I'd definitely order a new set from someone who knows what you need (whatever that might be) perhaps starting from standard and adjusting up as required.

For info, note there are other sources of info including here and others sellers -
http://www.distributordoctor.com/distributor_advance_springs.html

For setting up timing and how many degrees what and where have a look in the Archives here as there's lots of info from some very knowledgeable people and some of the info you might see generally is not necessarily the best.

You've got the right approach you're getting on with it and you're now found and accepted there's often more to restoration than many would have you think so it may not seem it but you're better off than before.
Nigel Atkins

One of the springs should be slightly loose. It creates a kink in the mechanical advance curve at the point where the second spring becomes active.

Cheers,
Malcolm.
Malcolm Le Chevalier

Malcolm.
I see Moss do a set of springs and have - "This set of 5 specially selected advance springs will allow you to adjust your distributor to suit your requirements. For Lucas distributors only." So have do find which springs to use, I notice there are two silver and one each yellow, brown and red.
Nigel Atkins

Malcom

Yes indeed, as I understand there is a primary and secondary spring. The primary is the weaker spring and stretches first to give the first part of the advance curve, then the secondary spring comes in a bit later to give the kink in the advance curve.

It’s the secondary spring that’s corroded and loose. If I turn the advance by hand to the limit stops, the secondary spring still isn’t engaged.

Chris
C MADGE

OK, cool, sounds like you are all over it Chris.

Nigel, I did once find a guide to the dizzy springs. I bet I can't find it again. They sound a great way to waste many hours on trail and error testing :-)
Malcolm Le Chevalier

You might find this useful: <http://mgaguru.com/mgtech/ignition/pdf/tuning_lucas_dist.pdf>

Enjoy your turkey and then sit down and relax with an interesting read!
Peter Blockley

That looks a very interesting article though if you wanted to be precise you'd want to treble check all your instruments, readings and calculation, no fat fingers on the calculator.

There was one controversial, upsetting and possibly shocking assertion though -
“… breaker points should not be used unless there is some overriding reason to do so. Aftermarket electronic kits should be installed to eliminate breaker points whenever possible.”
- how very dare he.
Disgusted of Northampton

You could lock up your dizzy to prevent any effect of the weights and springs and then fit an Aldon Amethyst programmable timing unit which also has a programmable vacuum connection. Hours of fun trying to spot if any setting changes actually make a difference.
Graeme Williams

This thread was discussed between 06/12/2017 and 03/01/2018

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