Starter wire size question

[the shadow]

I recently put a 3G alternator upgrade on and want to upgrade the small feed wire from the solenoid to the starter with a larger #2 cable . n lew of the old Ford #4 wire due to slow "hot" start issues.
Do I need to up the wire size on the other solenoid cable coming off the other terminal or is that just a "trigger" wire its either a #4 or #6 now?
I'm also replacing ground wires to larger from the frame to block as they were small and deteriorate.

[rich grsc]

The kit provided wire is more than adequate, you not trying to start an 800 cubic inch diesel engine. If you have hot start issues, it's most likely the starter

[gbranham]

I had a hot start issue briefly after I got my car on the road. I added a ground wire from a starter bolt to the frame and put a heat blanket around the starter. No more issues.

[Rebostar]

You will want #2 wire from the battery through the solinoid to the starter. Basic elecronics/physics, increase in temp equals increase in resistance equals lower amprage to the starter, thus slower cranking RPM when hot. Using #4 in any section would be like using #4 for all of it. You want the entire line to carry the full amp load. Absolutely a requirement if useing a rear/ trunk mounted battery. I have found that the older Fords with the solinoid a foot from the battery and the starter a couple more feet from the solinoid you can use #4 cable like Ford did from the factory. Anything longer than 8 feet and your going to run into slow cranking issues when the motor is hot. My battery is in the left rear wheel well so #2 wire was required all the way to the starter. If useing the Breeze front mounted battery you could probably get away with #4 cable, but why risk it? Go with #2. Also you will want to use a heavy bonding braid or #2 cable for the battery Negative cable. The entire cicuit should be #2
When I installed my 1st trunk mounted battery, I used #4 cable. After replacing both the starter (twice), then adding a heat shield to the starter and changing the solinoid, I finally fixed the slow cranking while hot issue with new #2 cable.

Happy Trails

[Dave M]

Agree with Rebostar. Had hot start issues almost from the start. Tried a heavier ground from frame to one of the starter mounting bolts that didn’t help. After putting a heavier wire from the rear mounted battery to the solenoid the problem went away.

[CraigS]

I 'think' you have an old style starter w/ a separate solenoid mounted somewhere on the firewall or footbox. If that is the case all the above recommendations will definitely help. But one more upgrade is to go to a new mini-starter w/ it's built-in solenoid. Wire it like this.
219905
This is from a Ford TSB on how to upgrade an old Mustang. It uses the firewall mounted solenoid as a starter relay.

[BUDFIVE]

“Shadow” your original question was about the “other solenoid cable coming off the other terminal or is that just a "trigger" wire ”.
If I understand you, this is the wire from the “crank” or “start” terminal on the ignition switch. This wire carries very little current and I’ve not heard of needing to change from the wire size in the RF Harness, Light Blue color marked “Start Sol”. I am using this wire to fire (trigger) the solenoid with no hot start problems. I am also using a mini starter with #2 AWG copper for the power and ground starter wires.