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MG MGA - Electronic Ignition Conversion - Again

My rebuilt original 1500 distributor has just arrived back from Aldon. They have reprofiled it for my 1800 engine and fitted the Ignitor (Petronix) electronic ignition.

In the previous thread on the subject one poster said to fit a Lucas sports coil and open up the plug gaps to 32/35 thou. Having spoken recently to both Aldon and Bob West the consensus is an emphatic 'no' on the Lucas sports coil - a standard coil will do the job just fine. Aldon did say that opening up a few thou may be ok - trial and error.

Any thoughts/advice from the community at large?

Steve

Steve Gyles

Aldon agreed with me that a lucas sport coil (DLB 105) would be fine, maybe they were getting confused with hi power electronic ignition type of coil. What does Bob know? (Joke, for those without a sense of humour) I run my plugs at 0.8mm (32 thou in old money)

Terry


P.S Sorry Bob
Terry Drinkwater

Steve. I have an engine analyzer which allows me to measure the HT voltage. I have never been able to measure a voltage, with the engine running, which was in excess of that a standard coil is capable of producing--i.e. 20K volts. A coil will only produce as many volts as the spark plug needs to spark. Normally, about 11K volts. A bad plug or bad lead can drive this upwards somewhat.

I am running Sports Coils because they came with the ignition kits I purchased, not because I believe that they do anything worthwhile. It simply made sense to replace various old coils with new ones since I had them on hand already.

As to spark plug gaps, the old .025" recommended gap seems to have been based on tests done by Morris and BMC back when the UK was still using "pool petrol" back after WW II. (My understanding was this was still used into the mid 1950's.) Not as good as the gas available in the US at the time where the standard plug gap was .035", nor as good as the various blended fuels we have today. I have been running .035" plug gaps for over 40 years with no problems. The engine seems to run somewhat better at that gap than the .025" gap and the additional voltage required is about 1K volts.

Les
Les Bengtson

I just put an aftermarket coil in a freind's MG midget 1500.

At the recommendation of the supplier, I purchased a Bosch "Red" Coil, which normally requires a 1.8Ohm ballast resistor, but when running with an electronic ignition, no resistor is needed. With points, the ballast resistor is needed to prevent premature pitting of the point faces.

I can't say that the performance has improved as the result of the coil -- the old stocker Lucas coil was working, and I did a lot of other work on the car which did have dramatic impact -- but I did put in new NGK plugs and widened the gap to 0.040".

I have not pulled the plugs to check them yet, but the car is running great. I will probably drop the gaps back to the recommended 0.035" when I pull them next. (I used 0.040" partly because I happened to have that size feeler gauge handy...and I am a fan of making big changes to see if they have any impact.)

One difference I did notice is that the new silicone 7mm coil wire seemed to not want to fit securely in the top of the Lucas coil -- but it snaps snugly into the Bosch coil which has a deeper throat at the top, so good enough for a reason right there IMHO. The new coil was about $39.00 US, and is slightly larger in diameter, so you will have to stretch the mounting ring a bit.

When I get my "A" running, I will upgrade to electronic ignition (if nothing else, you don't ever have to set the dwell and points again) and the same coil.

Just my $.02...

JIM IN NH
AJ Mail

This thread was discussed on 21/07/2006

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