396 Hot Start Issues

[James W.]

Now that the '65 396 Corvette that James West and myself have been working on is finished and successfully completely flight judging at the National Convention we want to get out and start enjoying this ride however a “Hot Start” issue has plagued the car and I’m looking for some input. I’m attempting to give as much detail as possible but I’m sure there are some items I’ll forget so please ask questions.

The cold start procedure works as it should. The engine comes up on the fast idle cam correctly and will hit about 1700rpm. After kickdown, it will hold an idle comfortably at 900rpm.
The car drives as it should. It has no hesitation at any speed and will pull without stumbling through all gears.
The timing is set at 10 degrees BTC and the engine has the correct Holley 4150 carb and we are running 110 octane leaded race fuel.
The ignition is the original distributor and the updated TI Solid State Amp with the 210 Coil (Dist/Amp/Coil Rebuilt or purchased from Dave Fiedler at TI Specialties)

The issue becomes once the engine has really reached operating temp and stayed there for an extended period of time. It tends to run between 190 and 210 degrees depending on air temperature. Once the car is shut down even for just a couple of minutes it is impossible to restart. It does not smell of gas and it will pump gas into the carb. It seems like it has a hard time turning over and you don’t get many tries as the battery tends to drain quickly. The Battery is a new Delco Unit. It’s almost as if the starter is using so much current there is not much left over for spark. We did change the 210 coil back to an original service replacement 207 GM Coil and that seemed to give a greater or hotter spark than the 210 coil, but it has not solved the problem. I have noticed that driving at dusk with the lights on the amp meter does show a discharge even under acceleration. I was planning on checking the voltage output from the voltage regulator thinking maybe the battery is not getting enough of a charge. With the lights off and driving the amp meter stays in the correct range. In either case the car will still not start unless it has sat for about an hour or slightly longer with the hood open to cool off.

Any comments or suggestions would be greatly appreciated.


Thanks,

James West and John Osterholm

[Joe L.]

Re: 396 Hot Start Issues

Now that the '65 396 Corvette that James West and myself have been working on is finished and successfully completely flight judging at the National Convention we want to get out and start enjoying this ride however a “Hot Start” issue has plagued the car and I’m looking for some input. I’m attempting to give as much detail as possible but I’m sure there are some items I’ll forget so please ask questions.

The cold start procedure works as it should. The engine comes up on the fast idle cam correctly and will hit about 1700rpm. After kickdown, it will hold an idle comfortably at 900rpm.
The car drives as it should. It has no hesitation at any speed and will pull without stumbling through all gears.
The timing is set at 10 degrees BTC and the engine has the correct Holley 4150 carb and we are running 110 octane leaded race fuel.
The ignition is the original distributor and the updated TI Solid State Amp with the 210 Coil (Dist/Amp/Coil Rebuilt or purchased from Dave Fiedler at TI Specialties)

The issue becomes once the engine has really reached operating temp and stayed there for an extended period of time. It tends to run between 190 and 210 degrees depending on air temperature. Once the car is shut down even for just a couple of minutes it is impossible to restart. It does not smell of gas and it will pump gas into the carb. It seems like it has a hard time turning over and you don’t get many tries as the battery tends to drain quickly. The Battery is a new Delco Unit. It’s almost as if the starter is using so much current there is not much left over for spark. We did change the 210 coil back to an original service replacement 207 GM Coil and that seemed to give a greater or hotter spark than the 210 coil, but it has not solved the problem. I have noticed that driving at dusk with the lights on the amp meter does show a discharge even under acceleration. I was planning on checking the voltage output from the voltage regulator thinking maybe the battery is not getting enough of a charge. With the lights off and driving the amp meter stays in the correct range. In either case the car will still not start unless it has sat for about an hour or slightly longer with the hood open to cool off.

Any comments or suggestions would be greatly appreciated.


Thanks,

James West ans John Osterholm

Jmaes------


Install a slave solenoid and your problem will be over "forever-and-ever".

[Leif A.]

Re: 396 Hot Start Issues

It sounds like your alternator is not putting out enough volts. With lights on your meter shows a discharge. You, also, state that you can't turn the car over very long without running down a new Delco battery. I would start by checking the alternator and voltage regulator. This may not address the "heat soak" issue you seem to be having, but IMHO you have a charging issue, as well.

[Mike T.]

Re: 396 Hot Start Issues

I'd agree with Leif, any time you have the amp gauge showing discharge, the alternator and voltage regulator would be the first items to check.

[Loren L.]

Re: 396 Hot Start Issues

Heat shield for the starter.

[Joe L.]

Re: 396 Hot Start Issues

Michael and Leif-----

If the charging system, including the alternator and battery, were at fault here, the car would have the same starting problem from cold as it does when hot. In fact, cold start would probably be even more difficult. So, while the car may have a deficient alternator, voltage regulator or battery, that's not the source of this problem.

This problem is usually caused by heat-induced, high resistance in the purple wire from the ignition switch to the "S" terminal on the starter solenoid. A properly installed slave solenoid is a 100% cure.

[Mike T.]

Re: 396 Hot Start Issues

Joe - That's true, he doesn't have issues with a cold start or any driving issues when underway but I wouldn't have expected the amp gauge to read that low solely on the purple wire experiencing heat related resistance. Regarding the remote solenoid, no doubt that would work too but I don't think the factory wiring setup on a Bigblock is prone to this kinda problem, there have to be plenty of them running around with no hot start problems. Of course, that could also mean that the wire routing is not secured where it should be.

[Joe L.]

Re: 396 Hot Start Issues

Joe - That's true, he doesn't have issues with a cold start or any driving issues when underway but I wouldn't have expected the amp gauge to read that low solely on the purple wire experiencing heat related resistance. Regarding the remote solenoid, no doubt that would work too but I don't think the factory wiring setup on a Bigblock is prone to this kinda problem, there have to be plenty of them running around with no hot start problems. Of course, that could also mean that the wire routing is not secured where it should be.

Mike-----


Resistance in the purple wire would have no relationship to the ammeter reading. As I mentioned, the car may have a charging system problem but it's basically not related to the hot re-start problem.

Big blocks do have this hot re-start problem. In fact, many years ago folks were having this problem with 454 engines installed in motor home chassis. So, what was GM's advice on a fix? Install a slave solenoid. They never specified this fix for other chassis applications but it's the solution for those, too.

GM tried a couple of other fixes for the hot re-start problem in Corvettes and other cars. In 1968, they added a heat shield for the on-starter solenoid for big blocks. Later, they released a solenoid spring that was supposed to solve the problem. Neither "fix" reliably and consistently solved the problem. The slave solenoid will solve the problem 100% of the time.

So, why do some cars have this problem and others do not? That I do not know. But, I know that when a car has the problem, the slave solenoid will solve it permanently.

[Bill W.]

Re: 396 Hot Start Issues

James . I had the same problem on my 62 FI and a friend also had it on his 67 400 horse . We sent the starters off to John Pirkle and told him about the hot start problem . Im not sure what he did but the problem was fixed after the rebuild . The 67 did need a new set of battery cables , the spring rings would get very hot when cranking .

[Joe L.]

Re: 396 Hot Start Issues

James . I had the same problem on my 62 FI and a friend also had it on his 67 400 horse . We sent the starters off to John Pirkle and told him about the hot start problem . Im not sure what he did but the problem was fixed after the rebuild . The 67 did need a new set of battery cables , the spring rings would get very hot when cranking .

Bill------


Once-upon-a-time when I had this problem. I replaced the starter several times including one BRAND NEW GM starter. They would solve the problem temporarily but it would come back sooner or later. When I installed the slave solenoid, the problem was gone for good-----even on hot restarts in Death Valley in the summer.

[Jimmy G.]

Re: 396 Hot Start Issues

John Pirkle Rebuild it to a High Torque spec Or just buy another starter (non matching) and put it on. My 67 390 AC car absolutely would not start after I drove it any distance. Now after the Pirkle majic Never failed to start. Just make sure you have a GOOD battery because it will need it Amazing difference

[Timothy B.]

Re: 396 Hot Start Issues

Could a starter shim help with this hot start problem. Do you think it's worth a try, easy to take back out.

[Duke W.]

Re: 396 Hot Start Issues

The timing is set at 10 degrees BTC and the engine has the correct Holley 4150 carb and we are running 110 octane leaded race fuel.

Any comments or suggestions would be greatly appreciated.


Thanks,

James West and John Osterholm

What is the total idle advance? You measure that at idle speed with the VAC connnected, and it should be about 25 degrees, but is it? Less than mid-twenties total idle advance will increase operating temperatures at idle and light load and increase the propensity for fuel percolation. With total idle advance in the correct range, the exhaust manifolds should measure no more than 500F with an IR gun.

AFAIK the carb vacuum advance port is full time, but the original 201 15 VAC doesn't meet the Two-Inch Rule because your idle vacuum is about 14" @ 900 and the 201 15 requires 15-16" to pull to the limit. A 12" B26 VAC meets the Two-Inch Rule.

Hard hot starting could be an indication of percolation, Leaded race gas should not be as much of a problem as pump gas, but try the flooded engine procedure. Wire the heat riser valve full open.

Beyond the above I agree that you should check out your alternator/regulator. Check system voltage at hot idle speed with increasing electrical load. It should not exceed 14.5V at light load and not be less than 13V at high load.

There have been a number of percolation threads including examples of insulating fuel lines with before/after IR gun readings that showed significant temperature reductions.

Duke

[Gene M.]

Re: 396 Hot Start Issues

Joe,
How, please explain the electrical circuit used for the slave solenoid and how it makes a difference. You may be wiring it differently from what I imagine.

Mike Hanson explained the solenoid workings and I understand it as I have "restored plenty of them. His previous posting on the subject says: "When the solenoid washer contacts both the battery and motor terminals in the solenoid cover, the rest of the entire vehicle electrical system is out of the picture and has nothing to do with slow cranking. Current flows directly through the washer to the field terminal of the motor."

This is understandable to anybody that has tore down a GM starter solenoid. But I can't understand how a slave solenoid is going to increase energy to the starter.....?

PS I have also run into this hot start issues with BB and high torque gear motor starters. And to all reading this, this is a good and interesting thread.

[Dan D.]

Re: 396 Hot Start Issues

Jim, measure the battery voltage with the engine running and after it has run for a while. It should be about 14.4V. If not you have a alternator/VR problem. When the battery sets for a while it builds up a residual charge, which is your cold start. If the charging system is not maintaining the 14.4V, then the battery is being drained after supplying ignition current and whatever else for a period of time.

I offer this suggestion because you say it struggles to turn over and drains the battery quickly.

If the battery voltage is being maintained at or around 14.4, then you have two problems. Hard cranking (starter, battery or wiring), and no start (ignition or fuel related - as others have suggested).

-Dan-