V8 with transistor ignition

[68conv455]

What is a transistor ignition? How do I know if I have one.
Thanks.

[joe_padavano]

There will be a finned aluminum electronics box mounted under the hood with a sticker that says UHV ignition or something like that. Also, if you remove the distributor cap, instead of points you will find a star wheel and mag pickup that looks amazingly like the ones on an HEI. The difference is that this will be in a conventional small-cap Delco distributor. Also, the coil is unique to the UHV system and is painted red, not black. The cap was also red originally but may have been replaced over the years. This system was only used on 67-68 Oldsmobiles and similar year Corvettes.

[Olds64]

Wow! You learn something new everyday.

[citcapp]

Joe,

What don't you know about Oldsmobiles..........................Always great infromation reading your respones to questions

[Oldsguy]

What he forgot...............(about 2% of his total Olds knowledge) I gained in a deal with the big guy upstairs.

[88 coupe]

Originally Posted by joe_padavano

There will be a finned aluminum electronics box ........

Capacitive Discharge Ignition (or CDI). Similar, in operation, to the MSD box, we are all familiar with.

Originally Posted by joe_padavano

........ This system was only used on 67-68 Oldsmobiles and similar year Corvettes.

Ford, Chrysler, and American Motors, used similar systems in their "Performance" cars. After market was also selling them.

Norm

[joe_padavano]

Originally Posted by 88 coupe

Capacitive Discharge Ignition (or CDI). Similar, in operation, to the MSD box, we are all familiar with.

Actually, not quite. The MSD box works with both points and electronic trigger. The purpose of the MSD unit is to provide multiple sparks for a single trigger event (hence the term Multiple Spark Discharge). Yes, there are now boxes made and marketed by MSD that also perform the spark trigger function using various crank-trigger or distributor-trigger systems, but the original MSD was simply an add-on to any existing spark trigger system.

There were also add-on CDI units that would work with a points-type trigger. The capacitor provided the voltage to the coil, but the discharge was still triggered by the points. The original intent of CDI was to extend the life of the points by reducing the current passing through them.

The Olds/Chevy Ultra High Voltage system was a precursor to the coil-in-cap HEI. The purpose of the UHV system was to do away with the points in addition to providing higher spark voltage. The UHV used a Hall-effect sensor and eight-point start wheel on the distributor shaft, just like the later HEI units. The differences from the later HEI units were an external coil (with different windings from a normal points-style coil) and the external control electronics. The amazing thing is that the design went from the relatively large external box used on the 67/68 cars to the small module that fit inside the distributor in 1973.