Fitting auto ignition to replace CDI system

[wilgil]

Hi all - after reading through all of the posts here, I have gathered that it might be possible to fit a standard kettering ignition if the CDI dies and no replacement is available. I am guessing that the surface discharge plug will have to be retired and replaced with 'normal' protrusion type plugs due to the lower voltage. i have a mid 70's 90HP Chrysler that someone has attempted to retrofit this way, but I see that they forgot to fit a capactior/condenser across the points.
I plan to use a transistorized Ignition with an automotive coil.

Does anyone have any suggestions for the type of plug I should use and any other things i need to think about? As mentioned in another of my posts, i have recently acquired 5 Chrysler engines and would like to get them all going - as soon as I get a block and tackle in my garage to lift them onto brackets so i can work on them!

 

[Frank Acampora]

Re: Fitting auto ignition to replace CDI system

Be very, very careful with the plugs. The surface gap plugs are dead cold. If you use regular bent electrode plugs they will almost always be hotter and you run the very real risk of melting holes in the piston crowns.

As far as the coil, if you use an auto coil be certain you get a 12 volt coil. Most autos before electronic ignition used a 9 volt coil with a dropping resistor. This was to compensate for the battery voltage drop to 9 volts during cranking. The resistor was bypassed during cranking and used during running.

With the surface gap plugs, it is possible to use a standard points and coil ignition BUT idle and starting may suffer a bit. They will run well at cruising speed--say above 2000-2500 RPM. So, try them first--you might be surprised.

The guy to ask about this would be Franz, over at The Chrysler Crew, tomorrow night Thursday) at 9-11 PM eastern USA time, at the chat room. Down there, are you on the other side of the date line? If so, compensate. Franz has forgotten more than I will ever know. Ahem! With 5 Chryslers, you really need to join The Chrysler Crew. Ahem! Ahem! I have somewhere between 15 and 20 of all sizes (including some Forces), some in pieces, but most work. Look for Dhadley on other boards on this forum. I think he is from NZ too.

Anyway, It's a bit of a moot point because there are still used CDI boxes floating around and available. You just need to look a bit harder for them. AND----You can always convert the Chrysler to older Mercury electronic ignition or newer Force ignition. Old racers used the Mercury ignitions on their Chryslers. Lots of options.

 

[wilgil]

Re: Fitting auto ignition to replace CDI system

Thanks for that - I remember reading an old post from someone who said that the only way to sort the ignition was to retrofit it as I am suggesting. I have about 4 'spare' CDI's, but I think they are all kaput. It's a pity that they are so well sealed up, making it very difficult to replace the offending component/s. The last time my CDI died I tried the only two that were available to me from the outboard wreckers ($250NZ ea), and neither worked - when I returned them, I wasn't allowed a refund, and he just put them back on the shelf for the next victim! At least I have a credit there now - unfortunately he refuses to service Chryslers though, so I'll have to buy a lot of spare sparkplugs and oil!

I'm really just trying to find a low cost solution to the issue that there seems to be with the Chrysler CDI's. Last time one died I was going flat out and when the boat stopped (quite suddenly), I dislocated my shoulder and I will forever more have a 'loose' joint that still (after 4 months) gives me grief, especially at night.

To me it seems to be the major weak point of these otherwise fine, agricultural motors (my current love is a circa '75 105).

Thanks for your comments, and I will see what happens and if there is enough grunt to jump a spark across the surface discharge plugs. If not, what type of projection plug would you suggest that wouldn't be too hot?