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MG Midget and Sprite Technical - Ignition timing

This question has probably been asked many times before, but I can't find the answer in the archives. What is the correct timing setting for a 1275? the Haynes manual says 13deg BTDC, but I'm not sure if this is correct. I've just installed powerspark module. I checked the setting before installation and it was 10 degs.
Pete Ottewell

Around 7.5 BTDC static.

A
Anthony Cutler

It is completely worthless to give timing settings without stating static or running, and if running, at what rpm.
And, it all depends on engine and distributor specs.
5-10 static is a usually starting point.

FRM
FR Millmore

Sorry FRM, I should have been more specific. 1275cc engine, 25D dizzy, dynamic timing at 1000rpm.

Pete Ottewell

What is accuracy of measurement for the 1000 rpm? 10%? 20%?

That's why I choose static...

A
Anthony Cutler

Pete,
as has been put you need to allow for wear and tear of components and rev counter error

7 static

13 at 1,000 (vac discon)

these are good starting points then adjust as required you can usually hear when things get sweet

before setting timing you want to know the tappets aren't too far out and that (CB points) and spark plugs are clean and gapped correctly

whilst your at it you want to (lube and) oil the dissy

be very careful about fitting the delcaite module wires so that they dont chaff inside or out of the dissy or you'll probably get a hard to find misfire later

then of course you need to check, or possibly replace, (rotor) dissy cap, HT lead set

you may well also want/need to adjust the mixture next to take advantage of the better running

getting rid of troublesome CB points is always something I've done when I get a classic but you do need to be aware that you stil have an old, possibly very worn, dissy so don't expect miricales or things to be as book figures

good luck, I'm sure you'll soon get used to the benefits and wonder why you've letf it until now
Nigel Atkins

Pete-
Understand. I am old school and agree with Anthony, I set static, but examine distributor and fiddle. I actually bought a cheap timing light after over 40 years of using a test lamp, to set things without points, and a couple of weeks ago the damn thing died as I was checking an electronic converted car - Drat! Gotta buy a new one. But, you can usually check static by turning the IGN on, then turning the engine until you get a spark out of the disconnected coil HT lead.

FRM
FR Millmore

I can't set it static as I have fitted a powermax electronic unit instead of the points. Started off at 13 deg dynamic at 1000 RPM vac disconnected as Nigel suggested. Took it for a run and it lacked power. Got home and advanced the dizzy until the revs picked up, took her out again and it was much better. Checked it with the strobe and it's now running at 20 deg BTDC with no pinking. difficult to see the timing marks on the crank case though, so I'm not entirely sure that my reading is correct. Should I push it further?
Pete Ottewell

whilst we wait for FRM

assuming (always, always dangerous) you've got all your other settings and compoments working well mark the present position as it is working well at the moment and try a little then take it for a run going through the whole range and go up hills slow and fast, sudden acceloration, ect.

decide if you think you need to further adjust the timing or mixture

remember to allow for variances don't have anything at it's limit as running conditions can vary greatly

so do you prefer CB points or electronic

don't forget to let go of the starter key sooner now too
Nigel Atkins

Pete

You should be abe to set any electronic system statically; they should act on the same basis as a mechanical points system.

I've done this with an Aldon Ignitor (vey good system) and also with Luminition (not so good).

A
Anthony Cutler

Nigel, Mixture is set with colortune and throttles ballanced out. Valve clearances set. The engine seems to be more stable and responsive with the electronic ignition. However, the main reason for fitting an electronic was to negate the need for setting and re-setting the points.
Pete Ottewell

so the engine is more stable and responsive, pressumably (dangerous to do so of course) better starting and tickover and you don't need to fit and readjust those fiddly points - you'll possibly have got better mpg but in reality you'll never know because you'll be pushing the car that much harder without realising

the CB points fan will say once a good set of points is fitted to a good dissy after an intitial adjust they're set until they need servicing and they'll usually get you home if you fiddle with them and that once the electronic igniters go it's a relay home (they're usually the ones who know of people who have fitted the igniters poorly or had them fitted so many years they can't remember how old they were fitted

I don't know if you still need to lube the cam for your unit but you'll still need to oil that ancient dissy
Nigel Atkins

I'm under no illusions that electronics can fail Nigel. That's why I'll be keeping a set of points and condenser with the tools needed to refit and set them in case the electronic unit fails. The unit I've fitted is the one in the attached link
http://www.simonbbc.com/electronic-ignition-kits/powerspark-mg-electronic-ignition-kit-lucas-25d
Pete Ottewell

IF fitted correctly and not later damaged the electronics tend to works for years and years without fuss or attention - unlike most CB points

I note the unit has a 'red' rotor arm so hopefully that'll last a few years before needing change

if you used the car more or were more used to its performance potentential I'd say get used to this then consider dumping the old dissy all together

I fitted an Aldon Igniter head because at the time they didn't do a 123 for 1275s - just my luck - then a matter of months later there was a 123 for the 1275s - just my luck - held up for 6 months just to get the right hand cap required - just my luck

I swapped from Aldon Igniter head in old dissy to full electronic 123 dissy, what a difference, for once i was actually in good luck

I put a very expensive Lucas electoronic ignition with amplifer on my prevoius Spridget nearly 20 years ago after the then new CB points closed up on me when I was out for a run, I don't believe in unreliable classics - bought a spare whatsit, vane rotor as I was told that was the only bit that ever went wrong

I've always got rid of CB points on the classics I've had i only enjoy driving them not the macho stuff of head under the bonnet at the side of the road
Nigel Atkins

I will assume the 20 deg is at the same 1000 rpm, since you did not say. That's a bit much for most 1275, and might indicate weak or broken advance springs. The most important number is max advance around 32-3500, should be not more than 32-34 without other odd factors.
I would suggest you get to a good RR operator with a distributor machine and get it right - ask Nigel. The cost will come back rapidly in fuel, performance, and not melted pistons.

FRM
FR Millmore

I seem to have got it right now as the performance is a lot better. I'm a silly old fool and was not reading the advance stobe correctly. I actually took the time to read the instructions and bingo. I also could't work out why the vacuum advance wasn't working until I discovered that the pipe had melted against the block. I've replaced it with a new one and new connectors.
Pete Ottewell

Pete
surely you're a bit old to be told to RTfM

>>until I discovered that the pipe had melted against the block<< that made me smile

well done on getting it sorted

we'll give it a year then offer you the chance to revert back to CB points the Daz challenge
Nigel Atkins

Nigel, lol. My wife will tel you that it's a bloke thing. I had read the fM but not obviously not understood it. on the second read through it became obvious where I had gone wrong. We all live and learn even at my not so tender years.
Pete Ottewell

Pete I'm well passed the stage of being able to remember the little I've learnt and even when I did know a little I'd make the same mistakes over proving I'd not really learnt anyway

good on you for sorting it and admitting you made a mistake (that bit is beyond some)
Nigel Atkins

This thread was discussed between 29/07/2012 and 10/08/2012

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