starter bogs when hot
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Intermediate
Joined: Dec 2005
Posts: 33
Likes: 1
From: Charlotte NC
starter bogs when hot
Greetings. My '78 Vette has a 383 in it. Starts very well when cold. After driving for 30 minutes or so it barely starts. Starter bogs, I have headers. Would it make sense if I were to put a Ford starter solenoid in the engine bay? Also, I could wrap the headers with heat shield. The starter, alternator and battery seem fine. Any ideas or suggestions would be appreciated. Thanks.
Popular Reply
Apr 27, 2025, 07:49 PM
Tech Contributor
Joined: Aug 1999
Posts: 14,379
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From: At my Bar drinking and wrenching in Lafayette Colorado
The real problem with the Vettes experiencing hot-soak starter problems is the length of the battery cable and the size of the cable. Over the years, many of the cables have been replaced with "standard" automotive cables, which are 4-gauge or 2-gauge. The Corvette cables, due to the length, must be "0" gauge minimum, with "00" even better. Check your cable gauge and make sure you have "0" gauge cables or bigger.
Lars
Lars
Race Director
Joined: Nov 2006
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From: Sunshine Coast, Queensland, Australia
2025 C3 of the Year Finalist - Modified
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Cruise-In VIII Veteran
Would it make sense to add a Ford starter relay, No.
would it make sense to wrap your headers. That's never a good idea.
Is the starter heat shield in place?
Another good idea is a later model mini starter or gear reduction starter. Also with appropriate heat shield.
would it make sense to wrap your headers. That's never a good idea.
Is the starter heat shield in place?
Another good idea is a later model mini starter or gear reduction starter. Also with appropriate heat shield.
Le Mans Master
Joined: Aug 2017
Posts: 8,336
Likes: 2,810
From: Cool Northern Michigan
ecpirate,
Those headers get mighty hot and come might close to the starter.
Look on Summit Racing for Starter Heat Wraps. I think Cool-It makes one as does Thermal Tech?
Insulated, foil laminated blanket that comes with two stainless band clamps. Wrap the starter in such a way that the end piece of the wrap is pointing towards the ground.
(In the event the wrap ever collects motor oil, it will drain easily)
You could go one step further and insulate the starters wire harness also. The tube / sleeve comes in three feet lengths, cut to desired length.
The wires will need to be removed from the solenoid to slip the insulated sleeve over the wires.
And if you are feeling really ambitious, remove the starter, and on your workbench swap out the solenoid for a heavy-duty unit. (NAPA)
The end cap is brown in color, indicating its ceramic. Handles heat much better.
Those headers get mighty hot and come might close to the starter.
Look on Summit Racing for Starter Heat Wraps. I think Cool-It makes one as does Thermal Tech?
Insulated, foil laminated blanket that comes with two stainless band clamps. Wrap the starter in such a way that the end piece of the wrap is pointing towards the ground.
(In the event the wrap ever collects motor oil, it will drain easily)
You could go one step further and insulate the starters wire harness also. The tube / sleeve comes in three feet lengths, cut to desired length.
The wires will need to be removed from the solenoid to slip the insulated sleeve over the wires.
And if you are feeling really ambitious, remove the starter, and on your workbench swap out the solenoid for a heavy-duty unit. (NAPA)
The end cap is brown in color, indicating its ceramic. Handles heat much better.
Melting Slicks
Joined: Oct 2003
Posts: 2,187
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From: Chapel Hill NC
2025 c3 ('68-'73) of the Year Finalist - Unmodified
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Id stress test the battery and throughly check/clean the battery cables/connections, the connections at the starter and the grounds.
Le Mans Master
Joined: Aug 2017
Posts: 8,336
Likes: 2,810
From: Cool Northern Michigan
If you do end-up removing the solenoid wires:
Take a photo first.
Then mark / tag all wires with masking tape & a Sharpie where they came from and go back to.
Some solenoids have four posts for wires.
Don't get it wrong.
Take a photo first.
Then mark / tag all wires with masking tape & a Sharpie where they came from and go back to.
Some solenoids have four posts for wires.
Don't get it wrong.
Old Pro Solo Guy
Joined: Dec 2017
Posts: 8,079
Likes: 4,431
From: Marlton NJ
Do you still have the original style starter in it?
They are very susceptible to heat soak, especially from headers.
It is because they use an electro-magnet, powered by 12v, that loses power when hot. As the large copper windings expand from heat.
The newer style mini-starters use permanent magnet motors, Usually rare earth.
This style is much stronger, and do not suffer from heat soak.
Many of them are gear reduction as well, which greatly increases their power, and/or lets them be smaller.
They are very susceptible to heat soak, especially from headers.
It is because they use an electro-magnet, powered by 12v, that loses power when hot. As the large copper windings expand from heat.
The newer style mini-starters use permanent magnet motors, Usually rare earth.
This style is much stronger, and do not suffer from heat soak.
Many of them are gear reduction as well, which greatly increases their power, and/or lets them be smaller.
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Verdad Gallardo
Tech Contributor
Joined: Aug 1999
Posts: 14,379
Likes: 6,390
From: At my Bar drinking and wrenching in Lafayette Colorado
The real problem with the Vettes experiencing hot-soak starter problems is the length of the battery cable and the size of the cable. Over the years, many of the cables have been replaced with "standard" automotive cables, which are 4-gauge or 2-gauge. The Corvette cables, due to the length, must be "0" gauge minimum, with "00" even better. Check your cable gauge and make sure you have "0" gauge cables or bigger.
Lars
Lars
Drifting
Joined: Jul 1999
Posts: 1,542
Likes: 43
From: Plano TX
Check all the wiring for sure. I had a similar issue with my 80 years and tried a number of solutions but never really fixed the problem 100%. Later found that the wire and or ignition switch could not supply enough current to the starter S terminal.
I pulled the wire from the S termianl and used it to energize a relay Id mounted on the firewall. Then connected a wire from the large battery terminal on the starter to one side of the relay and the other side back to the S terminal on the starter. No more issues.
I pulled the wire from the S termianl and used it to energize a relay Id mounted on the firewall. Then connected a wire from the large battery terminal on the starter to one side of the relay and the other side back to the S terminal on the starter. No more issues.
Drifting
Joined: Dec 2004
Posts: 1,714
Likes: 42
From: Austin Texas
^ I had this problem also. Here are the mods I made to combat the slow turning starter. So the solenoid would engage but motor would turn slow when hot.
1. Replace engine to frame ground with new thicker cable
2. Replace starter with new style PMGR
3. Add additional ground strap on starter to frame
4. Upgrade new copper battery cables to 1/0
Now zero hot start issues and the car has headers with no heat shield on starter.
1. Replace engine to frame ground with new thicker cable
2. Replace starter with new style PMGR
3. Add additional ground strap on starter to frame
4. Upgrade new copper battery cables to 1/0
Now zero hot start issues and the car has headers with no heat shield on starter.
Racer
Joined: Dec 2006
Posts: 417
Likes: 40
From: Swansea IL
The real problem with the Vettes experiencing hot-soak starter problems is the length of the battery cable and the size of the cable. Over the years, many of the cables have been replaced with "standard" automotive cables, which are 4-gauge or 2-gauge. The Corvette cables, due to the length, must be "0" gauge minimum, with "00" even better. Check your cable gauge and make sure you have "0" gauge cables or bigger.
Lars
Lars
A weak ground is more often than not an issue many ignore.
Team Owner
Joined: Jan 2006
Posts: 37,637
Likes: 3,118
From: Crossville TN
Starter "heat soak" is NOT a real thing. But, getting inadequate current flow to it when the engine is hot is possible. But the cause is MOST LIKELY due to a missing/defective/rotted-wire grounding wire running from the frame to the engine motor mount. THAT is the source of electrical ground for the starter. Bad wire/connection/etc......poor starting. As engine heats up, so does the ground wire and that means higher resistance in the wire. If that ground cable is OLD, replace it. When you remove it, you will find why the starter wasn't getting adequate current when hot.
Melting Slicks
Joined: May 2021
Posts: 2,271
Likes: 1,316
From: Fleming Island, FL
If you have a slow cranking and you want to check the integrity of the cables between the battery and the starter a "voltage drop test" will reveal any issues with the cables whether they be bad, too small, or bad a connection. There's plenty of videos on YouTube on how to perform this test. Heat soak is a real thing and the bushings supporting the armature are the cause. When these bushings are worn the armature can rub the field magnets as the starter heats up.
Team Owner
Joined: Jan 2006
Posts: 37,637
Likes: 3,118
From: Crossville TN
How does heat affect wear in the starter bushings????? If it does anything, it would help to REDUCE clearance in those bushings. But, if you calculate the affect of heating of shaft journals and bushings when temps are increased 100*F, the change is negligible.
The C3 starter (GM's go-to for decades) was designed to handle engine compartment heat. If your car is having trouble starting when hot, look elsewhere for the problem.
The C3 starter (GM's go-to for decades) was designed to handle engine compartment heat. If your car is having trouble starting when hot, look elsewhere for the problem.
Melting Slicks
Joined: May 2021
Posts: 2,271
Likes: 1,316
From: Fleming Island, FL
Team Owner
Joined: Jan 2006
Posts: 37,637
Likes: 3,118
From: Crossville TN
You need to bone-up on your heat transfer calculations. A 1/2" steel shaft will expand a grand total of less than one-thousandth of an inch when temperature is elevated 100*F. Somehow, I just don't think that's going to stall a starter...
