Change Coil or junk ballast system?

Post your technical queries / problems here!
Post Reply
Message
Author
JohnE
Posts: 35
Joined: Wed Apr 20, 2011 6:24 pm

Change Coil or junk ballast system?

#1 Post by JohnE » Wed Aug 08, 2018 1:50 pm

I am working my way through some of the previous owners (or maybe ones before) "updates" to my car.
It's fitted with a resistance wire in the ignition feed (the pretty common ballast arrangement) to step down the voltage during running to about 7 volts (as measured by me on a multimeter).
I checked the resistance of the coil that's fitted and it seems to be 4.1 ohms - which if I can use google properly, suggests I have the wrong coil fitted as that's closer to the 3 ohms expected for a 12v coil, rather than the 1.5 ohms for a 6-9v coil.

I am considering just doing away with the ballast (wiring past it) as it's easier than buying and fitting a new coil.

Other than originality (and a small advantage to cold starting) does anyone see a reason to keep the old ballasted version?

User avatar
Atodini
Posts: 16
Joined: Thu Feb 21, 2013 6:21 pm
Location: Mansfield Notts.
Contact:

Re: Change Coil or junk ballast system?

#2 Post by Atodini » Wed Aug 08, 2018 4:19 pm

Advice here depends on what car it is and the engine size really. With a small (under 1000cc) engine a ballast system really isn't necessary but with a bigger engine, if you want it to start easily in cold weather, it's quite useful..... Either way the first thing I'd do is renew the coil as 4 ohms is really too much and suggests a problem with it somewhere.

What I would advise though is that a modern electronic conversion would be the best option but bear in mind that a cheap solution is just that - cheap and can often cause more problems than it solves. The budget systems do not cope well with heat as they are built with simple normal electronic components, whereas the higher end systems use much higher tolerance "weapons grade" components. I would tend to avoid "Powerspark" or "Accuspark" as although some people have had excellent results with these, probably just as many have not. Be aware that the replacement distributors these companies advertise are generic, the advance and vacuum curves are unlikely to be correct for your engine.

I use an Aldon system on my car - pretty much bullet proof. Before that I had fitted a Lumenition Optronic, a used system I'd bought new in the mid 1970's to use on a racing motorcycle, and this too is bullet proof (but care is recommended to carefully mount the control box well away from heat)'. I ran this on it for upwards of 25 years with no problems, racking up an epic number of miles.....

I only changed it after fitting a stage 2 cam, after which we found that the factory Lucas 45d distributor was incapable of providing sufficient advance to get the best from the cam - I now have a fixed distributor with the advance and vacuum advance being taken care of by an Amethyst module.

Any electronic system limits the supply current so can be used with either a ballast or non-ballast coil, though a normal "performance" coil is best. Coils are not too expensive but beware of some online sources as such items are often cheap far-eastern clones.

John
"I thought I was wrong once - But I was wrong"...

JohnE
Posts: 35
Joined: Wed Apr 20, 2011 6:24 pm

Re: Change Coil or junk ballast system?

#3 Post by JohnE » Wed Aug 08, 2018 4:26 pm

Cheers - it's a 4.7 V8 (AMC) - but I almost never start it in winter, and when I do it seems to start fine so not too worried about cold starts.
Also not my daily car so no need to worry about getting to work etc if it won't start.

I already have a contactless (electronic) dizzy bought off a mate for £75 - I think it's pretty reasonable - he bought it from the USA I think and only changed as he wanted something flashier.

User avatar
Atodini
Posts: 16
Joined: Thu Feb 21, 2013 6:21 pm
Location: Mansfield Notts.
Contact:

Re: Change Coil or junk ballast system?

#4 Post by Atodini » Thu Aug 09, 2018 12:57 am

AMC I know little about but as it's already got an electronic ignition, then this will work better fed from 12v rather than the 7v or so it gets through the ballast wire. On most cars this will connect to the back of the ignition switch, so I'd disconnect it from there, then run a new cable from that point to the switch side of the coil, disconnecting the ballast wire there as well.

As a contrast, I simply have an 848cc (Reliant Kitten), but the mileometer is now well into its 6th lap (in my long ownership)!! I did have the engine professionally rebuilt by Hans Kirama about 5 years ago though, to a much higher state of tune than standard.... Also had the chassis galvanised and modern disc brakes, servo, poly bushes and gas shocks so it's now well capable of keeping up with "moderns" in daily use. Last rolling road session it was doing 40bhp at the rear wheels plus 60mpg at 4000rpm / 70mph, not at all shabby for a car that only weighs half a ton..... Standard these struggled to do 40bhp max at the crank.

Image

John
"I thought I was wrong once - But I was wrong"...

Post Reply

Who is online

Users browsing this forum: No registered users and 1 guest