C3 Ignition

[Jack Corso]

My 68 427/400 is a TI car without the TI (it was removed before I bought it)with the current points distributor installed, would a coil with an internal resistor be required. The engine seems to be breaking up a low speed. Thanks,

[Jim Trekell (22375)]

Re: C3 Ignition

Jack from what I know the 68 was the first year for the factory wire harness to have a resistor wire connected from the firewall connector through the wiring harness to the coil. This resistor wire replaced the earlier type resister that mounted on the the firewall having a 12 volt supply wire and reducing the voltage going to the coil.
I don't know if your TI original wiring harness used the resistor wire like the other 68 and later Corvettes with points. I would think that it would not since there was no reason to reduce the voltage.
Look at the wire going to your TI coil. Is there a coated cloth type protective covering on the wire or just a regular of covering that is used on other wiring in the car? If it is the latter, then the wire is not a resistor wire needed to reduce voltage to keep from burning the points.
If you remove your points and they look burnt, replace them and if the low speed problem is gone you have a couple choices.
Convert your 68's distributor to TI like it was originally which may cost a few dollars, but with todays improvements may be more dependable that the original developed unit. You can visit www.tispeciality.com and see what is available.
If you 68 does not have the resistor wire you can go to a recycle yard, junk yard, etc. and locate a pre 75 GM car and remove it starting at the firewall wiring/fuseblock and remove it from the wiring harness tape assembly up to the coil and install it on your 68.
Another option is just install a pre 68 type resister on the firewall like earlier Corvettes with points. They are reliable, some are still in use today from factory installation.
Reference previous posts about electronic ignitions, they save maint time and money spent on points. A spare old point set stored in the glove box/storage compartment will always get you home if the points ever fail.
In August 1986 I installed Moroso Blue Max spiral core spark plug wires, Champion RJ12YC sprark plugs, ACCEL dist cap and rotor, Delco Uniset points on my original owner 68 that had 76235 miles on it. Today it has 96500 miles on it starts immediately, runs really great using the wires,spark plugs, cap & rotor, and points I installed in 1986. Cannot complain about a convential ignition system.

[Jack Humphrey (17100)]

With the TI option....

the standard engine harness was modified (mods are shown in the Assembly Instruction Manual) and a supplemental TI ignition harness was added. If the conversion from TI back to stock Kettering ignition was done RIGHT (TI harness removed and mods made to standard harness were undone), all should be right in the world!

It is CORRECT there was no discrete ballast resistor used on any Corvette in '68 (TI cars never used a discrete ballast as the function was incorporated into the TI wiring harness)....

To fault isolate the ignition system (is it an issue of spark that's causing performance problems?), why not drive the car to a competent shop that can execute a test run on an engine analyzer? Being able to see the spark waveforms on a scope at various RPM ranges is the quickest way to confirm/deny electrical ignition problems....