I stopped at a store yesterday in my '26 T coupe. Ran inside and back out in less that 5 minutes. Turned key to start and got one revolution of the engine, then nothing. Wouldn't turn the engine over. The volt meter was reading 12.4V. Couldn't figure why it wouldn't start with that much voltage. I sat there and waited 3-4 minutes, and then it started normally. What could be wrong? Is it the starter going bad? I have a new starter, but I don't want to change it out if it is not the problem. Electrical problems are my weakest skill area. What do you say?
Am I correct in thinking that you have just rebuilt the engine? If so, what compression ratio are you running? Sounds like there might be too much compression for the starter when the engine is hot.
I built the engine. 355 SBC. It does have 10.2:1 compression. It has 7K miles on it now, and this is the first time that happened. But I don't think that high compression is the problem. I used to have the hi compression problem with my 13:1 race motors, but this acted different than that.
Check and adjust your timing. Try advancing or retarding it looking for a sweet spot where the engine will turn over when hot. A heat soaked starter will behave this way also.
Recheck the battery ground to the engine/starter. The full 12.4 volts may not be reaching the starter, which is most important when engine is hot.
Round up the usual suspects…… Grounds Battery Cable size…. Box store cables are for Hondas. The old style starters need good size cables. They don’t have to be gigantic but they need to be large enough. Check all connections As Pete said, engine timing Double check grounds again, maybe you need more Battery, sometimes a dead cell will show fully charged Charging system
My vote is ground problem!! I would remove, clean down to BRIGHT metal and replace both battery cables. Also, I had a truck [semi ] once that would sometimes act that way. The nut holding the cable onto the starter stud had loosened up! Tightened that rascal and never had that problem again. Ben
The timing is set at 16 degrees initial, 18 degrees mechanical, 34 all in at 2800. Vacuum advance adds 14 degrees. Arrived at after a lot of experimentation. With the lake style headers, the exhaust goes nowhere near the starter, so exhaust heat-soaked starter is not the problem. Hot start has never been a problem before. That is my first thought also. Starter going bad is my second choice. Grounds are the easiest thing to check. I do have an overkill grounding system in the car. but ground could still be the problem. I know that grounds seem to be the problem about 90% of the time with electrical problems, hence the overkill on the grounding system, I'm sure of my timing, I keep up on it. Cables are large welding cable. Not sure of the gauge, but plenty large enough. Alternator at 14.59 volts. Just checked it. I think it is either ground or starter. Going to get out that new starter, put the car on the lift. It's only about 15-20 minutes to change the starter out whether it is bad or not. Will ck my ground system in the process. Then check them again! I almost got stranded yesterday. Don't want to have that happening. It's doubly embarrassing when you built the car yourself!
If you’re using the old style GM starter with the solenoid on top it may need serviced. The solenoids need clean copper surfaces and can be easily rebuilt using no new parts; only cleaning an possibly turning over the studs. Was the engine at full temp? 5 min will heat sync a starter.
If the voltage stayed at 12.4 and the starter didn't turn, your problem is not compression, timing, or anything mechanical. It is an electrical problem in that you have a bad connection. It could be anywhere between the key switch and the starter ground. It could even be internal to the starter. Voltage drop testing will pinpoint the problem. Without knowing how your start circuit is wired, it's hard to tell you how to conduct a voltage drop test.
I agree with @pprather that you should start with your ground connection......actually both ends of the cable. I'd also check the stud for the ground where it screws into the engine. They sometimes get corrosion on the end that threads into the block and cause an intermittent problem or complete loss of ground. Had that happen on a truck where I worked. They had it towed to a dealer who fixed the connection (supposedly) and charged for replacing the stud. They really only cleaned the external part of the stud and put the cable back in place. A week later, no start again. Maintainance man crawled under the truck and removed the stud. It obviously had not been replaced due to the corrosion. We sent a picture of it to the dealer. I'd get some jumper cables and have a friend follow you while you drive about the same distance and return home before shutting it off. Then see how many times you can start it. Hopefully its something simple like that.
Sometimes SBCs tend to have starter alignment weirdness. I’m just remembering the old junk I drove in High School. I can still hear those Chevy starters hitting hard and sometimes grinding. The parking lots were full that music in those days.
I absolutely hate intermittent electrical problems. I have tried many times to get it to not start again, hot and cold. I have Ohme'd out every cable and connection in the ground system. All good. 12.83 volts at the battery and 12.83 volts at the starter. Starts every time. I can't fix it if it ain't broke. I'm just going to throw parts at it and change the starter and put a set a jumper cables in the trunk
Just skimmed the thread. But it could also be a weak battery. I'd load test that first. It has enough amperage to start when cold. But not enough when it's hot. I've seen several batteries do this in the past, while showing good voltage.
The 12.4 was after a couple of failed start attempts. The battery now reads 12.83 which is right about where it should be. 12.4 should still start the engine.
A fully charged automotive battery shows a resting voltage of 12.6 volts when the engine is off. While the engine is running, the alternator boosts the voltage to a range of 13.5 to 14.5 volts. I would also do a load test on battery.
It’s always interesting to me when threads like this pop up when I’m going through the same thing. I replaced my stock olds 303 with a high compression 303 and am running into the same problem as op. Btw, am running original 6v starter although it has been rebuilt.
Another good test is to turn on the headlights when it doesn't crank. If the headlights go out when you try to crank, you probably have a poor connection at the battery. I had a 64 Chevy truck that was sometimes slow crank when hot. A voltage drop test on the positive cable to the starter showed that the 10.5 volts at the battery (during cranking) resulted in 8.5 volts at the starter. Replacing the positive cable cured the problem. Wait, but there is more. When I was putting my Model A together, I had the Buick engine installed and cobbled up enough wiring to fire it up for the first time. It cranked slow. I figured the 30 year old starter was bad so I took it apart and it looked like new. I took the solenoid apart and flipped the contact disc. Put it back on and it still cranked slow. That's when I realized that I had used a positive battery cable that I found under my work bench. Yes it was the one off my 64 Chevy truck. New cable, problem solved. I could have found this if I had done a quick voltage drop test.
Quicky parking lot test. Not ironclad but reasonable probability of putting you in the right area. Turn headlights on. Bright--good battery. Dim--low battery Headlights on, crank engine. Headlights stay bright--no current getting to starter. Headlights go dim--excess current draw in starter circuit.
See if it replicates. Take the same drive. Mine is doing this same crap. Retarding it doesn't help. I'm gonna change the starter.
@jaw22w When this kind of issue happens , you need to think out side box , What kind of starter are you using Big 87 ish older Or Oem Mini or aftermarket ? Make or carry a Remote start button, Or screw driver , pocket Knife . It can be Key switch , if like pre 68 If on column the actual ignition switch that's on the steering column itself. Ground , Positive Armature Solenoid Battery Volt drop . How hot was it that day & engine temp , Start Duplicating if you think it was too hot, You already know it's electrical problem start at the starter and work backwards. If a afraid to drive, let it sit and run for an hour , a way to overheat the starter Butane torch , But you kinda need to use common sense heating / heat sink the starter. if you know your ignition is true 16° that's not that high or too far advanced. I am starting a blower motor with 10:1 & 11:1 static compression with 24° of initial timing, street driven And I also have a remote button just in case then I start the engine like you would do with a magneto ,rotate motor three or four seconds I flipped the power on , on a mag you killed the ground ,, Open ground When it does what you said ,I think first thing I would do Head light test, Then remote start With key off Main stud on starter to Solenoid key off & On See if engine spin's over Normal As long as Bat does not drop close to 12.1 to 12.2 v should still spin engine fast enough to start , I have had engine combos using 6-8 hp starters Gas and alcohol/methanol
The problem with mechanics is most aren't. I'm not. But I'm going to ask, are you running points or HEI?
Point or HEI would not matter ""Unless" Advance plate stuck and the initial timing by being stuck is way over 25 Ish plus degrees & coolant temp over 200F But if you have a "Remote " start button Even @ Lock 36 , You would push button have engine spinning about four seconds flip power to ignition and it will start providing that the battery is not dead anything above 12.2 V
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