68 442, 455 engine
Motor was rebuilt last winter and runs great. However I have been having a heat soak problem with the starter. The old " it hardly cranks over when hot, after it cools, motor starts fine."
Now back to the battery... when engine is not running I measure less than 12 volts on my dads old meter (scale, not digital) ….with engine running at idle, looks to be about 12 volts... with throttle, 1000 rpm and up etc. it measures at 14 PLUS volts.
Battery is 2-3 years old, was out of the car during the rebuild but was kept charged. It recently ran down flat after somebody, Not me, left the headlight switch on for the interior lights.
Are these measurements of the battery voltage in a healthy range or could they be contributing to the hot start problem, ie not enough voltage for a hot start?
Thanks, Ben

 

Here is a chart on battery voltage. If you are less than 12v its not a heat soak issue, your battery is in need of a charge. Your alternator above idle is fine, I'm wondering if you have the stock setup or a 1 wire.

 

My dads 442 does this same thing as yours.
His is the positive wire to starter. It lost the sleeve m, it gets too hot off the exhaust.

 

1. Make sure you have a high torque big block starter. Make sure it and the solenoid are in good shape. Have it bench tested looking at amp draw. Disassemble and inspect. Rebuild if necessary. Do yourself a favor and purchase an HD truck spec solenoid. One off a 3/4 or 1-ton GM truck 366 or 454. Install the ground brace thats always missing on the starter.
2. Both battery cables need to be in good shape with low resistance. Replace with OEM spec cables. Not chineasium harborjunk.
3. The grounds need to be clean and tight. The neg battery cable should be grounded on the block below the drivers head.
4 Get a heat shield for the solenoid.
5. Load test the battery. Fail or weak replace.
6. Make sure the timing isn't to far advanced.
7 Get an exhaust blanket for the head pipe and wrap it from the flange down the pipe past the starter.
8. A healthy charging system should be outputting 13.8 to 14.2 +.5/-0. Have the alternator bench tested and check its connections?
9. Replace the analog point style voltage regulator with a digital unit. Transfer the OEM lid to the Digital and only you will know.

https://www.summitracing.com/parts/the-11620/overview/ < I think this is the size I bought.

https://www.walmart.com/ip/NEW-START...9033/127206152Google < I know its wally world. This is for example. A good non big box parts house will be able to cross ref the HD sol.

https://www.summitracing.com/parts/oer-361443 <<Mini heat shield. Don't be tempted to wrap the whole starter.

Do or inspect all of this and your hot start electrical problems will go away. In the pics note how the blanket is up against the manifold flange. Also, note the mini heat shield around the solenoid. Once I did all of this 15 years ago I not ever had a hot start problem. My cables voltage reg alt etc are all in great shape. This is in my 68 442 with its numbers matching mostly everything.
The rusty 455 shows an original low miles high torque starter with the ground strap/ brace attached.

 

The hot start problem is usually caused by excessive voltage drops in the starter and associated wiring. This can be caused by worn brushes, pitted contacts in the solenoid, dirty or corroded connections, or old battery cables that are internally corroded. In addition, worn bushings in the starter can increase drag and contribute to the problem. Usually this is the "death by a thousand cuts" problem, where any one of those will not cause a problem, but all of them together add up to a no-start condition. Be sure your starter is in good shape. Be sure your battery cables are correctly sized and not undersize replacements. Be sure your battery terminals are clean.

 

Thanks for all the great info.
Let the games begin.......

 

Start simple. Battery correct size? Cables good clean and tight? Starter bench tests OK? A cable can look OK and present high resistance due to age and hidden corrosion under the wire casing typically up at the battery.

 

Thanks for all the help, This problem truly was "death by a thousand cuts" as Joe P put it,,,

With the help of a digital multi meter I was able to see battery was not up to par. Replaced, on warranty,
Checked the Alt and found it to be not so great, Replaced with, of all things my original 68 Alt that I had put aside years ago. Now it charges SUPER.
Looked at the battery cables and the Positive was damaged down near the starter, Cables Replaced, Why not, may as well while I'm here...
Took the starter off, I haven't tested it but it's not too expensive of a part so I just went ahead and replaced it with one from NAPA,
Heat wrapped the starter and cables too...

And what-do-you-know
It works well now, No heat issues.

If only winter wasn't just around the corner.

 

Thanks for updating us Ben. Nice to hear that sound advice still works and you didn't go and install some other relay system or latest and greatest band aid.