Marlette73

Newbie. I viewed some posts about coils and ballast resistors but can’t seem to find out what type of resistor to use for my ‘73 455. It’s a bone stock engine that I’m putting in a rat rod so I’m kind of putting it together from scratch. I’ve seen a lot of resistors that all look the same but apparently drop the voltage in different ways. (???) I don’t want to burn up the coil by putting the wrong resistor in.
Thanks

rocketraider

You want something that drops 12v down to about 7 volts.

EZ way if you have enough clearance at the back of the engine is to pull the points distributor and install an Olds HEI distributor, which runs on full 12 volts. HEI was optional in 1973.

oldcutlass

It depends on the resistance measurement of the coil. You want to measure the coil resistance and the ballast resistor difference should equal 3 ohms. So if your coil resistance is 1.5 ohms then your ballast resistor needs to equal 1.5 ohms. 1.5 + 1.5 = 3

cfair

My ‘66’s were born with points & there are lots of good arguments in favor of them. Having said that, I’ve really enjoyed the improved performance from HEI distributors which need only switched 12v to the distributor, eliminating the worry about ballast resistors & burning points.

On the plus side my figuring is that GM got better performance and longevity from HEI vs. points or they wouldn’t have switched in ‘75. Of course the emissions landscape was changing, so they needed to evolve to get the engines cleaner. HEI is a slightly cleaner install too, everything sits on the distributor and you can eliminate one of the starter motor wires.

On the downside, these days the HEI distributors have to much vacuum advance designed in and it’s a good idea to carry a spare module since they die without warning. Also, if the great nuke EMP pulse ever happens, points will work and HEI will not.

Good arguments on both sides, suit yourself & be happy.

Cheers
cf

Marlette73

Oldcutlass Thank you! This is the exact info I need as I am not very good with electrical!

oletrux

So.....in the '72 model I would think they ran a points style ignition, thus there should be either a resistor or resistance wiring in place........does that make sense? How would you check that? Measure the voltage on the positive wire at the coil?

joe_padavano

Olds used a resistance wire built into the harness from the firewall connector to the coil. That wire is typically pink and black.

oletrux

Thanks Joe. I'll check that later today. The engine swap is generating many questions for me........the 403 had an HEI and the 455 is setup up with a points style.......and of course the car's wiring is a mess. I'll probably become a pain in the *** for you before it's over.........LOL.

Sugar Bear

Run OE GM resistance wire... hopefully a member can give a measurement on the length. Remember you want full voltage while cranking. Factory picked the full voltage from the starter solenoid.

Good luck!!!

joe_padavano

Yeah, unfortunately it's tough to know what the PO was thinking or doing. If there is no resistance in the harness wire, you can use an aftermarket ballast resistor instead for points. That makes it easy to swap back to electronic if you ever want to.

oletrux

Thanks Joe, I'll check the voltage on that rogue black/solder/red wire (which I am certain was hooked up to the hot side of the HEI. I'll expect to see 12V, and if so I'll install the ballast resistor. Should I expect to then see around 6V coming our of the resistor, or do they come in various levels of voltage reduction? I'll go after voltage because it's just me working.......

joe_padavano

Actually you want about 9v at the coil in the RUN position.

Sugar Bear

A resistor will only cause a voltage drop when current flows/there is a load. Putting voltage to the resistor without any load will have the same in/out voltage measurement. Check it with a load.

Good luck!!!

oldcutlass

In other words with the points closed.

deadeyejedi

This is what i used in my 72 had no issues with it .Im now running hei on the 72 but still use the ballast points and coil setup with the engine on my test stand.

oletrux

Thanks.

Sugar Bear

It would be best to measure the voltage at the coil with the car running to account for the points open and closing and to take the increased voltage from the alternator into account.
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oletrux

Thanks guys, this is an installation and converting from a HEI to a point-style setup. I just want to make sure of my power source and not damage the car or it's components.