MG-Cars.net

Welcome to our resource for MG Car Information.

Recommendations

Parts

MG parts spares and accessories are available for MG T Series (TA, MG TB, MG TC, MG TD, MG TF), Magnette, MGA, Twin cam, MGB, MGBGT, MGC, MGC GT, MG Midget, Sprite and other MG models from British car spares company LBCarCo.

MG MGA - Distributor Micro Adjuster

Simple questions relating to my refurbished distributor and new pertronix ignition.

Are the linear micro graduations on the vacuum body to any particular unit of measure. e.g. degrees? Or are they simply convenient reference marks?

Secondly, when setting up the distributor prior to installation would I be right in setting the scale to its mid point so that I have equal adjustment available to adv/ret?

However, I already have the unit installed and engine running. I have done the dynamic timing but am not convinced with my road tests that it is quite right. Greater tendency than before to run on after switch off and a slight feeling of a flat spot when putting my foot down from low revs.

On the latter point I having been leaning the mixture a bit so the flat spot may not be the electrics. Also, I have just installed a 3.9 diff so maybe I am being too critical in drawing direct driving habit comparisons with previous 4.3 performance.

Steve
Steve Gyles

Steve, here it is right out of the owners manual- "Each graduation on the barrel is equal to approximately 5 degrees of timing movement and one graduation is equal to 55 clicks on the knurled nut". Seems like you are on the right track with set up also, that way if your on the road,and if you have to advance or retard you have some leeway. In a side note I looked this up in my original shop manual and none of this was mentioned. I knew I'd had seen this before, went out to the car and found it in the owners manual. On our modern cars,after we've gone thru pages of warnings and cautions,we are told to return to the dealer or if we think we are smart enough to do something our self,we buy the shop manual at over 100 US.If we are lucky you only need 1,my Mustang had 3 volumes. Good luck Steve hope this helped. Gary
gary starr

Steve

Yes a good idea to set micro-adjustment midway. Your flat spot could mean you are a bit too advanced, low on dashpot oil or lean mixture. You should try advancing the timing to just below pinking at low revs. Ideal use of micro-adjustment (11-clicks/degree)

The running-on might be solved by:
a) Using colder plugs.
b) A good fast run can burn off glowing carbon and you may find running on does not occur then.
c) Richer mixture could cool things.
d) Have you tried a tankful of Shell's new V-Power 99 octane fuel (Optimax was 98)
d) Try letting the engine tick over for 30-40 secs before switching off to cool things down.
e) After this cooling down, try depressing the clutch pedal as well to increase drag on engine.
f) Ensure lowest tickover speed so it stops ASAP.

Let's hear how you get on. From what I have seen, don't even think of an anti-run-on valve.

Have a good weekend.

Pete
Pete Tipping

Gary

Many thanks for the info.

Pete

Some good thoughts there. I was thinkng it might be a tadge far advanced and that is why I wanted Gary's data before I started fiddling. I normally use Optimax. I had not heard of V-power99. Bet it costs an arm and a leg. The engine does not pink. My current plugs are NGK BP6ES.

Steve
Steve Gyles

I went right through my fuel and electrics this weekend.

Carbs: Slightly out of balance; float levers a smidge too high. Leaned them both out, checking jet heights with a vernier caliper.

Started the car and immediately noticed very raunchy exhaust. It seems I have blown a baffle. I then found it was very difficult to set an exact advance at 4000rpm. The timing light was jittering plus or minus about 5 degrees. Could this be attributable to the blown exhaust or have I wear, for example, in the timing chain etc?

All that apart the car go quite nicely now, but I am suspicious that the blown exhaust is the cause of my apparent flat spot.

I have another question on the exhaust box (muffler) and will start a new thread.

Steve
Steve Gyles

Steve

The timming variation you are seeing is probably average. This sort of variation is usually attributable to a worn distributor - cam, optical or magnetic bits flailing around in clapped out bearings. Your timing belt will be tight with its tensioner, so forget that.

Re: That 99 octane V-Power stuff, I had to top up with some 95 rubbish to get home after the South Downs Run yesterday and it immediately started pinking like a machine gun, had to knock the timing back about 3 deg (33 clicks!) to shut it up - am off out for some more nice 99 juice. Think it's about 1p a litre up on Optimax which seems to have disappeared around here.

Pete
Pete Tipping

Steve,
Something is really wrong if you are bouncing around by 5 degrees at 4000 rpms. At that speed, your advance should be "all in" and vary no more than 0-1 degree. If it runs well, then the problem may be with your timing light? Some timing lights don't work well with solid core or low resistance plug wires. That could be the problem? Otherwise it could be a matter of a worn bushing, points plate pivot, or something else internal to the distributor/engine.
Jeff
Jeff Schlemmer

Jeff

Most interesting. The distributor is my original from my 1500 that I have just had totally rebuilt, recurved for my 1800 engine and fitted with the Pertronix electronic ignition. I have installed copper wire leads whereas I had carbon leads on the modified Austin Metro distributor that has served me very well for 9 years and has been spot on to time with my dial-in advance timing light.

I spoke with James at Bob West this morning and was told that they had stopped using my rebuilder as he and Bob had received back any number of dizzies in which the advance curves were way off. Typically they would go to 32-34 degrees of advance by 2000rpm instead of 4000rpm. James said it would seem that the rebuilder had run out of OEM springs, weights and bits and pieces. He advised me to refit my other dizzy!

Steve



Steve Gyles

Steve

This is the distributor you had done by Aldon, right?

Dominic
dominic clancy

Dominic

Yes. Needless to say I am a bit concerned. I will put a new exhaust box on first then have another check of the timing. I have to say that I was getting some strange readings with my timing light so I have not discounted the comments Jeff made about the plug leads. I really do want to keep the refurbished distributor on the car. Perhaps I may be able to swap some of the internal parts of my 2 distributors if the silencer and plud lead theories come to nothing.

Steve
Steve Gyles

Just put the old distributor back on. Performance immediately back to normal with no flat spot despite blown exhaust baffles.

Looks like a call to Aldon to discuss their advance profiles and what they are going to do about it. Seems Bob West is correct and the ignition was advancing to maximum at a little over 2000rpm.

Not a happy teddy. Cost a lot of money to have refurbished and rebuilt.

Steve
Steve Gyles

Dominic and all

I misheard James the other day. I understood he was referring to Aldon. Infact he said Holden! My sincere apologies to all for that.

However, I do still appear have the same problem with the item I received from Aldon as Bob West and James have had with Holden. I will be discussing the issue with Aldon shortly.

Is it yet another case of modern manufactured items (in this case springs and bob weights) supplied to these businesses are not up to quality?

Steve
Steve Gyles

Just spoken with Aldon. I described the problem. They got out the job sheet and immediately said "Awfully sorry, could you send it straight back. We will sort it".

Mmmm...Me thinks they spotted something!

Steve
Steve Gyles

Steve,

When you put the old distributer back and everything was OK, what were your thoughts on the 3.9 Diff?

Regards... John
J Bray

John

I had a couple of weeks driving with the 3.9 on my 5-speed box before I tried putting in the 'defective' distributor. Accelerating up through the gears was fine, able to hold in each gear longer. I particularlarly liked being able to hold 1st and second longer when drawing away from stationary. Accelerating out of corners can take a bit of getting used to - tended to find myself occasionally in too high a gear and needed to drop a gear for decent performance whereas it would not have been necessary in a 4.3. I guess like most things it just takes getting used to.

Steve
Steve Gyles

Steve,
There aren't many options for replacement weights on the market, but the spring qualities can vary wildly. Most of the "new" distributors available are using decent quality springs, but the installers are bending the springs to adjust the ignition curve (rather than using the correct springs.) Its easy enough to have new springs made, but getting them made within specification is difficult. There's a gentleman who calls himself the "Distributor Doctor" who has an enormous box full of OEM springs, if you know exactly what you need (wire gauge, 3 of loops, installed length.) He's somehwere in England - I'll have to dig through old emails to find his contact info.

Solid core spark plug wires can quickly be substituted for a carbon core lead just to set the ignition timing. Many times this solves issues with digital timing lights not functioning properly.
Jeff
Jeff Schlemmer

This thread was discussed between 07/09/2006 and 16/09/2006

MG MGA index

This thread is from the archive. The Live MG MGA BBS is active now.