10 replies to this topic

[Wakey-Dan]

How important is it? What does it do. I believe your supposed to use when fitting a new distributor elecronic ignition module.what would happen without it?

[zuluaga63]

Nothing bad should happen but its better to put grease to insure longer life in the distributor or at least to work more gentil

[Wakey-Dan]

Cheers zulu, thats good. I just didnt have any at the time. Ill pick some up when I can just to be sure.

[Alex_B]

It does what it says on the tin, it helps dissipate the heat from the electronic ignition module into the baseplate, cant comment on what would happen without it but I would use it if I were you :)

Edited by Alex_B, 15 March 2013 - 09:33 PM.

[Tamworthbay]

Is it the same as heat transfer paste as used on processors! If it is, any nerd world shop will sell it.

[Wise Old Elf]

http://www.maplin.co...al-grease-32411

[MRA]

If the heat is not dissipated and the module gets too hot then it will fail.

[tiger99]

The stuff sold for use on processors is perfectly ok. You most likely don't need the most expensive brand, "Arctic Silver" I think it is called, just a general purpose heatsink compound. The white stuff is fine.

[mini13]

Ive had a couple of these modules go bad on me before due to temperature,

in traffic the car would misfire like a b*&^*&^d and eventually cut out, once the dizzy had cooled off it would be ok again,

in general Semiconductors have a temp limit of approx 150 deg C, at least thats what the datasheets usually say, the ignition module has to dissapate a fair bit of wattage in heat into something thats already pretty hot (the dizzy body) so needs all the help it can get in the form of the heat transfer paste.

[Wise Old Elf]

We used to regularly change these modules back in the day. We always used the gel that came with the new modules and they still failed.
We changed hundreds of the Ford CVH engine ones. There was a time when the new ones were not working out of the box. We were never sure if they were very sensitive to spikes or they were just badly made.

I would always use the gel to be on the safe side.

[tiger99]

The failure rate of semiconductors, depending on type, doubles for every increase in temperature of around 5 to 10 degrees C. 7 degress is a good working figure. So the cooler you can make it, the better. As mini13 says, 150 deg is a commonly used upper limit, ideally you would want to run at well below that, however you will not get much below engine block temperature, or even near it, in a distributor. Your engine block temperature is effectively much the same as the coolant temperature, often somewhere around 90 degrees.

Personally, I prefer the old style electronic ignition systems where the clever bits are in a metal box with cooling fins that you can fit in a cool place, and only a small magnetic pickup is in the distributor. The old Sparkrite systems were like that, and repairable if they broke.