Coil question

[Jon White]

Anyone know if theres any difference between a 4cyl ignition coil and a v8 ignition coil??

I only ask casue I'm try to sort out why my V8 is sooooo cr@p in water. Witht he v8 in it my series is still running on the origional 4cyl coil that was on the vehicle when I bouht it!

It runs alright on the road, just hates water - just wondered if this could possibly have anything to do with it!

A quick hunt of the parts book shows different part no's for both but anyone know if theres actaully any difference?

Thanks

Jon

[02GF74]

Depending on your v8, some (most or all?) had ballast resistor so would mean v8 coil has lower resistance than the series one which I'm pretty does not have B.R.

If you measure primary resistance, 3 ohm is non ballast whereas 1.5 ohm would be for ballast and for efi.

I run v8 lumention that should not use the lower resistance coils so have LR coil. Not sure if that helped.

[Niall_CSK]

The V8 coil is actually a 6V coil, there is a ballast resistor built into the loom on Rangies & SD1s to drop the voltage to 6V when it's running, during start the ballast resistor is bypassed to get extra ooumph but not designed to run continously.

Don't know what the 4 cyl coil was. Thinking along the lines, if you used the loom for the V8 then you might only be sending 6V to a 12V coil. The wet environment combined with low revs might affect the performance.

[Jon White]

Nope - using the series 3 wiring loom, series 3 coil with no ballast resistor.

So is the lack of ballast resistor the only difference then??

Jon

[Niall_CSK]

As far as the loom is concerned I think so. Could be that the series coil is just not man enough for a V8

[02GF74]

Nope - using the series 3 wiring loom, series 3 coil with no ballast resistor.

So is the lack of ballast resistor the only difference then??

Jon

no, the lr and RR coils are different. the rr cold should not be run without ballast resistor; a good start would be to try a replacement coil, check/set the points and replace the condenser for a good ;un (but do it 1 step at a time to findthe bad component).

later look at king lead, dizzy cap etc.

have you look at spark itself?

[Jon White]

I appreciate you shouldn't run a ballast resitor type coil without a resistor and vice versa.

Points and condensor are fine having been recently replaced. There is no problem as such. It starts and runs fine, it just hates water.

I was just wondering if I was overloadig the coil or somehting by effectively making it spark twice as fast as it would on a 4 pot thats all.

Jon

[VERY OLD DISCO]

the coil on a 8 cyl works twice as hard as one on say, a 4 cylinder. The coil is just a crude transformer, the electrical field collapses when the points open and this "induces" a voltage in the secondary (high voltage) winding. If a balast is fitted it is usually a 6v coil, but when the starter is operated and battery voltage drops to , say 8v on a cold morning, the balast is bypassed and the coil gets about 8v, thats OK because its only for the short time required to start the engine.

So, check the voltages at the coil across + and - and see what you have.

If the coil gets very hot (and they do get quite hot, thats why they put them in an airflow) by which I mean to hot to hold your hand on, somethings not right.

Also check HT leads, or better still throw them away and buy some expensive silicone ones, Make sure they are the right ones, nearly righ wont do!

Good luck Geoff

[geoffbeaumont]

It starts and runs fine, it just hates water.

Sounds perfectly normal for a V8

[02GF74]

the coil on a 8 cyl works twice as hard as one on say, a 4 cylinder.

The coil is just a crude transformer, If the coil gets very hot (and they do get quite hot, thats why they put them in an airflow) by which I mean to hot to hold your hand on, somethings not right.

Good luck Geoff

I would disagree with all of the above.

It is unclear to me by what is meant by "works twice as hard", for sure an 8 cyl coil will be switched twice as much as a 4 cyl. The power going into it in any given time depends on on the input voltage and dwell angle (rpm and no. of cylinders only come into if the time period under consideration is very short). From what you say, it implies that the 8 cyl coild last for 1/2 the time of 4 cyl - can annyone confirm that?

The coil is a transformer but I wouldn't say it is crude. It is use in a crude fashioin by switching the input on off rather than applying a nice smooth sine wave, for example. If this was applied, you would get a nice sine wave on the output likewise a shophisticated and expensive transformer would behave in the same way if subjected to a switching input like the one to a coil.

If you do the sums, the amount of heat in the primary is hitting about 50 W - can you hold a 50 W lightbulb in your hand? From my experience my LR coil has never given me problems and when up to temperature is too hot for me too put my hand on it for maybe more than 10 secodns - I certainly cannot keep it on there (or that is how I remember it).

[pedant mode to annoy you off B) ]

[jules]

I thought it was 9V not 6v

Never mind I know nothing about electric's

the balance resistor is a little block about the size of a posh hotel box of matches made of porcelin(i think) that sits next to the coil look at the coil on a old 110 v8 and you will see it there.

Jules

yes my spelling is always this bad