manual says i need to connect it to 12v in order for it to work. where is the best place to connect it for the 12v?

holley 600 cfm carb

 

I assume you are talking about the choke?..Any keyed 12volt ignition source should work.I ran a wire out from an unused spot in the fuse panel on my old pickup..Do not hook it up to the + coil wire though..

 

yep its the electronic choke cable. it just says it needs to be connected to any 12v source. thanks

 

Any KEYD 12 volt source.

 

check if you have 12V+ at coil+ with ignition switch on. If you do, then you can take it from there. Stock distributor will obly have 7-8V there. So that's not working. And if it is it's not working right. Then you might want to use a connection from the alternator, which has the nice effect that it will only heat when engine is running.

In the end just make sure it's 12V, and that it's only carrying 12V when either engine is running or at least ignition switch is on. you don't want to heat the choke when engine off and key out

 

12v available at "I" solenoid post.
my car had an available unused plug under dash.
look for unused plugs and check voltage.
can T into oem plug w/ DIY T.
i never cut oem wires.


edit to add: "I" is hot but less than 12v if upstream ballast resistor

 

I thought the "I" solenoid post was only hot while cranking ......

What is the problem with hooking it up to the coil? Seems the most logical choice to me. I've heard it before, and the instruction sheet for my carb said not to, but I need to know why .......

 

The "I" post is hot when engine is running and off when key is out.

"I" on circuit that provides current to coil. Good idea to limit coil supply current thus a ballast resistor is required. Some coils have ballast resistor at coil with a full unregulated 12v supply to resistor.

some cars like my mustangs have a resistor wire under dash and limit current flow to the "I" post.

if your application requires a free flowing 12V then i recant using "I" terminal if your car has an upstream ballast resistor.

the coil +12v terminal will be down stream of resistor unless it is a coil/resistor combo.

clear as mud?

use multi meter to measure possible +12v sources w/ engine running.
verify 0V w/ engine off.

 

Large Lug #1 = always live high current capable approx +12v

Large Lug #2 = live when "S" post receives +12V signal; high current capable.

"S" post = approx +12V when key turned full clockwise.

"I" post = less than +12v when key in run; voltage depends on upstream resistor.

 

after thinking ...uh oh...
i don't like the idea of disturbing current flow to coil.
if after market device connected to coil wire draws too much juice it may suck coil dry...not good...

maybe an LED light bulb would be ok but not a device which is power hungry,,,