Sounds like a case of starter heat soak. I would check the condition of the brushes in the starter and the solenoid. Good idea to carry a spare starter.

 

Mine started doing the same thing, same symptoms... get hot, would barely turn over... one day, at Home Depot, I was showing The Judge to an old fella and I started to crank her up, and it went...wonk, wonk, and he said "your starter gear is bindin' on your flex plate"...he was right. One front corner of the starter was about 1/8" from the frame, and torquing, etc. had pushed it into the flex plate...

Ground off the corner, remounted, adjusted meshing clearance, and never had a problem again..

Theory is that with elevated temperature the flex plate expanded just enough to bind, but barely enough clearance when cold to work correctly... and yes I had the correct bolts.. it still moved.

Not saying that's the problem, but it's worth a look....

 

Doing a Ford starter relay conversion would probably help. Most of the time it's the solenoid that is the issue. As the windings in the solenoid heat up they become significantly more resistive and demand more electrical current to generate the same amount of electro-mechanical movement. Wired via the GM way, the key (or pushbutton) and low guage wiring can actually become a current limiting source and you will end up with extremely sluggish starter. The fix is to use an outboard Ford style starter relay. Your start wire now triggers the external relay kept well away from heat. It runs a MUCH heavier guage wire from the battery to the solenoid on the starter. The solenoid, regardless of how hot it is can now draw ample current from the battery.

That being said, don't discount getting a starter TOO hot. At some point extreme heat can delaminate winding coils and then you will lose effectiveness of the starter permanently.

 

Doing a Ford starter relay conversion would probably help. Most of the time it's the solenoid that is the issue. As the windings in the solenoid heat up they become significantly more resistive and demand more electrical current to generate the same amount of electro-mechanical movement. Wired via the GM way, the key (or pushbutton) and low guage wiring can actually become a current limiting source and you will end up with extremely sluggish starter. The fix is to use an outboard Ford style starter relay. Your start wire now triggers the external relay kept well away from heat. It runs a MUCH heavier guage wire from the battery to the solenoid on the starter. The solenoid, regardless of how hot it is can now draw ample current from the battery.

That being said, don't discount getting a starter TOO hot. At some point extreme heat can delaminate winding coils and then you will lose effectiveness of the starter permanently.

If the GM engineers had determined that a Ford type solenoid in series with a GM solenoid would solve that problem they would have designed it that way. That being said, yes the GM solenoid is the weakest link and a new one won't necessarily solve a heat soak problem. If the starter has any age on it the brushes are probably close to being worn out. That was the problem with the starter on my 76 Vette. I replaced the worn brushes, cleaned the commutator with light duty emery cloth and cleaned the rest of the starter and reassembled with a new solenoid and no more problems. The main problem with a GM solenoid is the electrical burning of the contact disc. Many moons ago the disc was reversible and once the contacts were cleaned you had a practically new solenoid. Doing away with that feature made GM more money. FWIW, the first GM starter I worked on was a SBC in my 36 Ford coupe in 1964.

 

no gm vehicle came with a ford starting solenoid, but every gm vehicle came with a metal shield covering the starter to keep exhaust heat from soaking in. most were discarded cuz it made it difficult to get at the starter bolts. most are designed to protect the solenoid on top of the starter. some just clip on the solenoid

i'd start there (pun intended)

 

Yall missed the part about "reverse mount". IE, NOT block mounted.

Next question, how is the header so 1 1/2" from the starter on the bell?
is that an under chassis header?
QM will look it over and fix what needs fixing. The other peeps are talking solenoid here but they don't know that QM bell mounted starter isn't your standard GM anything. Another relay isn't needed at all. EVER in my opinion.
What the PN? of the starter? Does it use a 6" flywheel or are you one a triple disk and using the QM flywheel?
Will it spin over when the ignition is off?
Next up....Wires. Heat is bad for em....When hot, they pull lots of amps. Clean all connections, bright and shiny. Use at least a 1 or guage wire. Stranded is best and you better have a really good battery too. I buy the wire in bulk and add my own lugs. $3/foot right now for welding cable ground wire at my local welding shop or hardware store.

 

Doing a Ford starter relay conversion would probably help.

The Phord relay is a band-aid. The solenoid on the starter STILL needs to function for the starter to work. All the extra relay does is add a failure mode while bypassing some resistance in the start circuit wiring. Find the resistance, correct it, and you won't need the band-aid.

 

Yeah I hear this all the time. So I will go ahead and put on my EE hat and set aside my other degrees in engineering and mathematics. The solenoid on the starter is a magnetic columnizing device. It doesn't care what the voltage is as long as enough current can be achieved to instantiate the magnetic field strong enough to induce enough EMF to drive the plunger in the valve body. In essence the solenoid wants a current source NOT a voltage source. However a car doesn't really have a current source it has a voltage source. The wiring from ignition source to the solenoid easily becomes a current limiting system. Small amounts of electrical resistance, even under the most ideal circumstances, can limit the maximum current draw. The Ford solution eliminates that. The much smaller solenoid required much less current to draw through the ignition system. And since it is wired directly into a battery source on the contactor side, the starter solenoid is free to draw as much current as it wants to move the plunger. I'm happy to sketch out the math for you if you would like to see it. I'm not saying this is problem ssanto is experiencing, I'm just saying I do this conversion for racers all the time and I have yet to see it not work.

If the GM engineers had determined that a Ford type solenoid in series with a GM solenoid would solve that problem they would have designed it that way.

HAHA. Ok I had to take a few minutes to wipe the tears of laughter from my eyes. If you genuinely believe that, then I have a 100 years of automotive mistakes to share with you. Design decisions like this in manufacturing come down to dollars and cents. Either on the part or in the assembly.

 

Adding an unnecessary component and more impedance to the circuit doesn't solve the problem, just makes the battery work harder.

 

Except for the fact that if you've got a trunk mounted battery even if it's fused, It is prudent to mount a Ford contactor so that the long starter cable from the trunk to the starter is not live all the time when you're driving. Can't hurt. But if the starter is close to the battery perhaps it's less of a consideration....

 

Adding more electrical components simply adds more points of failure , I've always preferred the K.I.S.S. principle .

 

Do you have such an arrangement in your car? Are you saying that electrically the battery is disconnected while the car is under power? How does the battery stay charged?

 

Two solenoids. First #1 pulls in when key is turned on. Powers up the fuse block and all else. Push the start button. Which pulls in both the starter/solenoid plus solenoid #2 to start. The cable from the trunk to the front of The Judge has no power on it except when starting. Has nothing to do with the charging system, which is protected with 70 amp fuse back to the battery with Two #10 wires. Also the positive terminal on battery has 250 amp on-line fuse. Works perfectly.

If I get T-boned it might be a tad safer, but still a bad day.

 

You seem to have this unwarranted fear of getting t-boned , maybe you should strap mattresses to the side of your car ! Maybe work out an AI system that has " Spidey sense" to protect you from being t- boned ( like an avoidance system) What happens to all the extra electrical stuff if the trunk is the point of impact , will it survive ? This stuff makes my head hurt !!

 

Back in the 1970s and 80s I ran big block chevys in all my vehicles. The 427 was the smallest in my 1967 El Camino. That El Camino and my 69 Camaro with a 6-71 blown 454 I used a Fjord solenoid on them to cure a hot "no crank" situation.

My 1973 3/4 ton truck with a 454 and the daily driver 69 Camaro with a 468 never had cranking problems hot or cold. Both Camaros had trunk mounted battery. The 3/4 ton truck and El Camino had the battery in the OEM location.

 

If you are really worried about an accident, it is several orders of magnitude more likely that you will be rear-ended by some clown who's looking at their phone and not the road.

 

Yall are out in the weeds.......ssanta got a real race car, he expecting to get hit, or hit, or he ain't going fast enough.

 

I typically just increase the wire gauge rather than add relays. In big aircraft space believe of not is a problem for wiring and hydraulic tubing runs. Wire is expensive and heavy so relays are used to reduce large gauge wire runs. On a cost benefit study the maintenance and replacement of relays is less expensive than hauling the weight around for decades of service life of long heavy gauge wire runs. The typical road vehicle doesn’t suffer from this problem of long, heavy and costly wire runs so just up gauging the wire is more effective than adding the greater complication of more electro/mechanical items like a Ford relay to operate a Chevy relay.

Bogie

 

I typically just increase the wire gauge rather than add relays. In big aircraft space believe of not is a problem for wiring and hydraulic tubing runs. Wire is expensive and heavy so relays are used to reduce large gauge wire runs. On a cost benefit study the maintenance and replacement of relays is less expensive than hauling the weight around for decades of service life of long heavy gauge wire runs. The typical road vehicle doesn’t suffer from this problem of long, heavy and costly wire runs so just up gauging the wire is more effective than adding the greater complication of more electro/mechanical items like a Ford relay to operate a Chevy relay.

Bogie

You are absolutely correct, as usual, when one considers that the general rule is that fuses are used to protect the wiring, not the device that it is connected to. But when the subject wire is a 15 foot 1/0 welding cable (1/2" copper) connected to a fully charged 12 volt battery, and something goes drastically wrong, the outcome can be significantly more horrific than being stranded because a relay went bad.

I'll stick with my fuses and relays/solenoids.

By the way, coincidentally I was texting with an old buddy of mine just yesterday....who also had a 49 but sold it recently... and he's damned glad he did.

The guy who bought it only a week or so later sent him the attached picture. He didn't have a wreck it just burst out one day.. and this is for you too, 2old2fast...

He didn't explain why it happened but it did.

Here's what happens when you short a battery:

And here is the photo that my buddy sent me.

I REST MY CASE!

 

The only thing the picture show is an unfortunate accident , proves nothing ..

 

Just goes to show that many people are forgetful, but no amount of relays or voo-doo wiring would have prevented it from happening. And besides just exactly does it have to do with the OP's problem?
He either need to rebuild the one he has or purchase a new one.