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Old 12-03-2014, 05:54 PM   #24
MARKDTN
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Join Date: Jan 2011
Location: Chattanooga, TN
Posts: 2,135
Re: 1972 does not turn over when hot

Quote:
Originally Posted by RichardJ View Post
MarkDTN you must be referring to this setup.




All switch's and relays have resistance. The ford relay adds resistance to the battery cable. The two extra cable ends and the nuts holding them to the ford relay can add extra resistance as well as two new points for possible corrosion.
The relay itself adds an extra drain on the battery at the S terminal.

You said "it just doesn't have to rely on the long length of purple wire to get power".

The purple wire is still just as long and instead of going to the S on the chevy solenoid, it goes to the S terminal on the ford relay.
The ford solenoid is actually just a relay, because it doesn't move the starter gear like the Chevy solenoid does. Now you have both.

The first drawing below, shows the basic chevy wiring. The Purple wire from the ignition switch goes to the S terminal and activates the solenoid when the key is turned. The battery is connected directly to the Chevy solenoid.

The second drawing shows the small Bosch type relay connected to the Purple wire. Current flows from the Purple wire, through the relay to ground. Less than 50 milliamps has to flow through the ignition switch and relay.

When the relay is energized, current flows from the 12 V source through relay terminals 30 to 87 and back to the S terminal on the chevy solenoid.

This relay wiring has far less drain on the battery and is much, much easier to install.

I understand all of what you said, but that is not how people fix a hot start problem on a Chevy with headers. That is not how Ford got their Delco starters to work with 429/460 power. The Delco starter solenoid uses much more amperage to pull in than the Ford solenoid. That is because the Ford solenoid only moves a contactor while the Delco one moves the starter drive in as well-which you said. That is why people hook up the Ford solenoid. The small Bosch relay alone may help, but you still have to overcome the starter drive pull in.

"This relay wiring has far less drain on the battery..." You should not have any drain on the battery with any of these so not sure why you say this?

"...and is much, much easier to install." Not really. You still have to tap into the purple wire, and battery power and ground. All of these options are ugly underhood and take away from the simplicity of the truck wiring.

I meant to add to my post that I would not do any of these. I would swap to a gear reduction style starter. Heat issues are greatly reduced.
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