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Distributor Removal for Points Replacement

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archangel Avatar
archangel Gold Member Ed Geissler
Houston, TX, USA   USA
I in the near future I will need to replace the points on my ZB. Researching the proper method I have discovered the following.

In order to replace the points it appears to be more convenient to remove the distributor from the car. The MG Magnette Workshop Manual, Section C.6 and the the BMC Autobook Three, pp 48 and 49 both instruct the user to "Extract the two bolts securing the distributor clamp plate to the distributor housing and withdraw the distributor." However in the John Twist "how To" video #31 he definitely guards against this and recommends loosing the clamp plate pinch bolt. This procedure is not recommended in both manuals as it interferes with the ignition timing.

A survey of other threads on the MGA and Magnette Forums produces results using both methods.Those who have tried removing the the two bolts indicate it is a real PITA. My question is which one is correct and causes the least amount of grief for the less experience owner like myself?

Ed

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david.g.h Avatar
david.g.h David Harrison
Stratford upon Avon, UK   GBR
1929 Austin 7
1932 Austin 7 "Cabbage"
1956 MG Magnette ZA
1989 Porsche 944 S2
My opinion....WHY?
Just change the points in situ! No need to worry about re-timing the engine
Dist cap off, undo the pivot nut (don't lose the insulator) and the plate clamp screw, replace, set the points clearance ....done,If you have the s0-called quick fit type they are pre set!
D

archangel Avatar
archangel Gold Member Ed Geissler
Houston, TX, USA   USA
Hmm!

OK that sounds like a reasonable approach.

Thanks,
Ed

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Ian Williams Avatar
., Derbyshire, UK   GBR
I agree. ..The only time I've taken a distributer out is during an engine overhaul...
Never to change points... that's my two-penneth. ..

Wray Avatar
Wray Gold Member Wray Lemke
., South Carolina, USA   USA
There are a couple of advantages for pulling the dist itself. One, you can clearly see all the mechanism and there is little chance of messing up the points. Plus, there's less of a chance of dropping the nut and screw when mounting the points. I had the nut fall off the wife's GT after I put a new set of points in with the dist in the car (must not have tightened it correctly). It's in the dist housing somewhere, I just replaced it and haven't had any problems.

On the other hand, you don't, as David says, have to reset the timing if you change them in situ. Then again, it probably wouldn't hurt to check the timing anyway.

paddyreardon Avatar
paddyreardon Paddy Reardon
Calne, Wiltshire., UK   GBR
1933 Morris Minor "Evie"
1956 MG Magnette ZA
Unfortunately either option for removing the distributor will lose you the timing position. Loosening the clamp means it's possible to put the distributor back in any position. Undoing at the two bolts on the clamp plate ensures the general orientation is retained. The clamp plate has slotted holes which allow about 20 degrees of timing adjustment without loosening the clamp. I tend to use this for timing setting as the clamp tends to wear out the distributor body if it's regularly loosened and tightened.

You could try marking the position of the clamp plate before undoing it. If you are very careful, you should be able to refit it within a half degree.

jimb Avatar
jimb Jim Brown
San Francisco Bay Area, USA   USA
1967 MG MGB
Even leaving the distributor in place, I don't think you could be certain of having the timing stay the same. A slight difference in point gap, or a slightly different rubbing block profile could easily change the timing by a few degrees. I can;t imagine changing points and not checking the timing.

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Roger17Martin Avatar
Roger17Martin Roger Martin
Colchester, Essex, UK   GBR
Ed,

On my B-Series engines I usually remove the dizzie with the two set screws so the clamp plate position is not lost and it is so much easier to work on a dizzie on the bench - better access, illumination and less risk of dropping small parts inside.
The only disadvantage is the set screw heads can be difficult to access and undo, especially if very tight. I usually use an open ended spanner/wrench used end-on and then turned with the jaws of an adjustable.

Others are correct in saying that the wriggle room on the slots means precise timing can be lost but if I am in a hurry (or just being lazy) I just mark the position of the set screw heads on the plate slots with something like typing correction fluid. That seems to work for me.
Lastly, I would recommend that if you adopt this approach you do re-check the points gap after the dizzie is back on the engine.

Happy Christmas.
Roger

B-racer Avatar
B-racer Jeff Schlemmer
Shakopee, Minnesota, USA   USA
1950 Willys Jeep Pickup "Ratrod"
1971 MG MGB
2014 Dodge Charger
ANY change in adjustments of the points will result in a change of engine timing. So pull it. It'll take far less time overall to pull the distributor, then you can see what you're doing. I repair a lot of severely damaged distributors from people dropping a screw or lock washer below the breaker plate unknowingly, then let it rattle around inside until it takes itself apart. Do it while clamped in the bench vice and save yourself the heartache and added expense.



jeff@advanceddistributors.com

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Luv Em Old Avatar
Luv Em Old Brian Radich
Auckland, Auckland, New Zealand   NZL
I always set my distributor with the slots in the clamp either fully clockwise or anticlockwise - depending on access to the clamp bolt. (Very inaccessible on an E Type Jag). The timing will not change when you replace the distributor with the slots the same way. I always remove the distributor when replacing points for the reasons others have mentioned here.

But as a matter of course you really should recheck the timing on the rare occasions that you remove the distributor.

archangel Avatar
archangel Gold Member Ed Geissler
Houston, TX, USA   USA
Has anyone installed an electronic ignition distributor such as the Pertronix Electronic Ignition System sold by MOSS? From the distription it sounds like it eliminates a number of problems we have been discussing.

gruntie Geoff Pollard
., Surrey, Kenya   KEN
I can't imagine not setting the timing after changing the CB points: the slightest change means a change elsewhere, QED.

Of course, one can then explore the delights of the DPO fitting a mis-matched timing chain cover and crankshaft pulley: not for the first time did I wonder if it was not easier to do things properly in the first place....

PS on something else I had a Pertronix system and a MSD 6AL: after 2 MSD units and trouble with the Pertronix I junked them both, had the distributor re-curved (a dying art these days) and fitted a Lumenition optical ignition system, such as the Magnette also has. Truly fit & forget, still spot-on several years later.

david.g.h Avatar
david.g.h David Harrison
Stratford upon Avon, UK   GBR
1929 Austin 7
1932 Austin 7 "Cabbage"
1956 MG Magnette ZA
1989 Porsche 944 S2
Speaking for myself I have never felt the need to remove a distributor to reset or refit points! Why go to that degree of complication...I find I am just as likely to lose or drop bits on a bench as when working on the engine! I was never entirely sure about the "quickfit" style of points replacement, but they do avoid forgetting to put the insulating washer back!
I had trouble cold staring my ZA. It didn't seem to matter where the choke was, it would spin over happily without starting and then as I stopped cranking would suddenly "catch" and run perfectly...good battery,points, condenser, leads, earths etc etc. Handle starting was OK , but hard work! So what to do???
The suggestion was that the starter was "absorbing" too much energy and thus starving the ignition system, so that when I released the starter (& the engine was still turning) it would then start as all the energy was then able to go to the ignition. Seemed plausible to me.
Anyway I fitted a Powerspark D8 complete distributor and a new Powerspark CS standard coil & set the timing. Problem solved. Car now starts "on the button" even after being left for a month in a draughty cold garage. They can be seen on http://www.simonbbc.com 01527 899453 (Simon!) in Bromsgrove & I found them helpful and knowledgeable.(No connection other than as a customer)
As an aside my car has a1600 block & ZA head, but was fitted with a 1622 distributor! (If anyone needs one it is in good condition & available at a very reasonable price!) I have also found a correct ZA distributor, now in my growing pile of "to keep" spares!

gerry22 Avatar
gerry22 Gerry McNulty
Nevada, USA   USA
1971 MG MGB GT "Sick"
1974 MG MGB GT "Rusty"
1979 MG MGB "BB"
By all means go electronic you will see the difference right away your dizzy is no doubt worn out

paddyreardon Avatar
paddyreardon Paddy Reardon
Calne, Wiltshire., UK   GBR
1933 Morris Minor "Evie"
1956 MG Magnette ZA
There is a company in the UK that produces brand new 25D Lucas distributors. They supply a ready to use electronic unit for £85 posted to the US (£10 extra for positive earth)

http://www.accuspark.co.uk/distributors.html

I have had one for the last 5 years without any hint of a problem. Could be a very easy solution.

Paddy

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