Looking or more guidance - Converting a Points FI distributor to TI

[Joe C.]

Ballast resistors

1963: Service Bulletin: Distributor Breaker Point Burning
Bulletin Number: DR #577
Date: February 27, 1963
Section: VIy
Subject: Distributor Breaker Point Burning
Models: 1963 Corvette and 409" Engines
To eliminate distributor point burning during cold-weather operation, a new higher value ignition primary
resistor entered production on February 4, 1963, for all 250 H.P. or 300 H.P. Corvettes and 340 H.P. 409"
Passenger Cars. If premature cold-weather point burning is encountered on the above models, built prior to
the production change, install resistor No. 1957154 (1.8 ohms) in place of variable resistor No. 1931385
(approx. 0.3 ohms resistance when cold).
Resistor No. 1957154 may also be used on 340 H.P. or 360 H.P. Corvettes, 400 H.P. or 425 H.P. 409's, and
the Corvair Spyder for temporary winter operation; however, it should be pointed out to the owner that
resistor No. 1931385 will provide the best possible high-speed ignition performance.

[Jim T.]

Re: Ballast resistors

I tried a electronic ignition in my 1970. Installed a Mallory photo cell unit in 1974. In 1976 my 70 would not start one morning. Pulled the distributor and installed the previously removed point system and the 70 started. Have not desired to change from the point system in my 68 or 70 since my experience with the Mallory unit. Removing the distributor cap for point maintenance also allows maintenance of the mechanical advance system. I did retain the HEI ignition system that came with the ZZ1 crate engine that I installed in my 70 in the early 90's. No problems with the HEI.

[Clem Z.]

Re: Looking or more guidance - Converting a Points FI distributor to TI

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dwell extenders work very well as they use a SCR to "close" the points electronically as soon as they open increasing the dwell time . one nice thing about them is if they go bad the car just keeps on running. i used them back in the 60s on race engines turning 7500 RPMs with just a single set of points shimmed to prevent point float

i added a drawing of how to build a dwell extender

[George J.]

Re: Looking or more guidance - Converting a Points FI distributor to TI

Most "ignition problems" are due to sloppy distributors or old, broken down plug wires. The distributor is the most overlooked component on vintage engines and most could use a good "blueprint" overhaul. As long as the shaft bushings don't need to be replaced, it's a fairly easy DIY job.

Remember the old adage: If it works, don't fix it.

Duke


Duke,
Amen.

George

[Brooks R.]

Re: Looking or more guidance - Converting a Points FI distributor to TI

Again, i want to thank everyone for the great info. I will admit, much of this will take a bit of chewing on my part to understand.

I think I will take the conservative approach and leave the points as they are since there is a lot going on with the engine build and the FI unit.

Don't want to make too many changes at once. I am however intrigued but the electronic dwell extender and I think I actually understand the concept.

I also like the fact that it fails safe such that the system just returns to the normal dwell condition.

Here is what I think I heard. The amount of time it takes for the circuit to close in a mechanical system is determined by the shape and height of the lobe, the relative position of the point arm to the lobe and the speed of rotation of the distributor shaft. With the dwell extender this is reduced electronically to about zero. I am guessing that benefit of this is that it provides more time for the system to recharge (so to speak) so that full energy can be delivered with the next opening of the points.

Please let me know if I completely missed the point. I have a thick skin and prefer the blunt truth. Thanks

[Clem Z.]

Re: Looking or more guidance - Converting a Points FI distributor to TI

Again, i want to thank everyone for the great info. I will admit, much of this will take a bit of chewing on my part to understand.

I think I will take the conservative approach and leave the points as they are since there is a lot going on with the engine build and the FI unit.

Don't want to make too many changes at once. I am however intrigued but the electronic dwell extender and I think I actually understand the concept.

I also like the fact that it fails safe such that the system just returns to the normal dwell condition.

Here is what I think I heard. The amount of time it takes for the circuit to close in a mechanical system is determined by the shape and height of the lobe, the relative position of the point arm to the lobe and the speed of rotation of the distributor shaft. With the dwell extender this is reduced electronically to about zero. I am guessing that benefit of this is that it provides more time for the system to recharge (so to speak) so that full energy can be delivered with the next opening of the points.

Please let me know if I completely missed the point. I have a thick skin and prefer the blunt truth. Thanks

you got it.

[Brooks R.]

Re: Looking or more guidance - Converting a Points FI distributor to TI

Thanks Clem, I think I will try and build myself one of these.

you got it.