Need help diagnosing studder/noise
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Team Owner
Joined: Mar 2003
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From: Wilmington N C
St. Jude Donor '14 thru '26
Need help diagnosing studder/noise
It's a '64 coupe w/original engine & transmission. Had this car 20 years, no problems. Started up normally. Ran okay for a mile then I noticed a kind of a backfire noise, but it wasn't a backfire. Chugged along for a second or two, then okay. Did this strange noise again, not a clicking, or shut off (like the dreaded red wire syndrome). Quickly turned around a came back home. All the plug and coil wires are snug. No corrosion anywhere that I can see. Red wire connection at the bulkhead is secure. Never heard this kind of a noise before, w/any car. Somehow, I feel it's an electrical issue, but I'm open to any and all suggestions. Many thanks. 
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It's a '64 coupe w/original engine & transmission. Had this car 20 years, no problems. Started up normally. Ran okay for a mile then I noticed a kind of a backfire noise, but it wasn't a backfire. Chugged along for a second or two, then okay. Did this strange noise again, not a clicking, or shut off (like the dreaded red wire syndrome). Quickly turned around a came back home. All the plug and coil wires are snug. No corrosion anywhere that I can see. Red wire connection at the bulkhead is secure. Never heard this kind of a noise before, w/any car. Somehow, I feel it's an electrical issue, but I'm open to any and all suggestions. Many thanks.
It is far more likely you need to start under the distributor cap. Try a fresh set of correctly gapped points and condenser, set dwell and reset timing. Replace the rotor and cap if they are so old you cannot remember putting them on. One other thing, inspect the wire connecting to the points which moves with the breaker plate and eventually fatigues. I've seen cars running on just one or two strands!
Points replacements such as Pertronix or similar often fail the way you describe, so if you have one of those that would be the first thing I would replace.
Dan
Last edited by dplotkin; Mar 13, 2025 at 11:35 AM.
Race Director
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From: Central Arkansas
In addition it could be the coil also acting up but just 1 mile down the road probably didn’t heat it too much. Usually they act after they are good and hot. But if points and condenser don’t fix it, the coil is worth swapping out.
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Team Owner
Joined: Mar 2003
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From: Wilmington N C
St. Jude Donor '14 thru '26
If the pop and mild backfire you describe came from the rear of the car than its likely ignition related. If you have not removed the distributor cap in 20 years, and you have the original breaker points ignition, its likely the points are worn and/or the condenser is shot. Bad condensers present as you describe your symptoms. On the other hand your symptoms if accompanied by a pop under the hood instead of the exhaust could indicate fuel starvation from a plugged filter or tank sock. But this is far less likely.
It is far more likely you need to start under the distributor cap. Try a fresh set of correctly gapped points and condenser, set dwell and reset timing. Replace the rotor and cap if they are so old you cannot remember putting them on. One other thing, inspect the wire connecting to the points which moves with the breaker plate and eventually fatigues. I've seen cars running on just one or two strands!
Points replacements such as Pertronix or similar often fail the way you describe, so if you have one of those that would be the first thing I would replace.
Dan
It is far more likely you need to start under the distributor cap. Try a fresh set of correctly gapped points and condenser, set dwell and reset timing. Replace the rotor and cap if they are so old you cannot remember putting them on. One other thing, inspect the wire connecting to the points which moves with the breaker plate and eventually fatigues. I've seen cars running on just one or two strands!
Points replacements such as Pertronix or similar often fail the way you describe, so if you have one of those that would be the first thing I would replace.
Dan
Melting Slicks
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Keep in mind, just because the condenser "looks" new doesn't mean it is working as designed..........
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Team Owner
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From: Wilmington N C
St. Jude Donor '14 thru '26
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On a distributor cap you want to look at the underside for carbon tracking. I think with a new set of points in a condenser you'll be good.
Dan
Team Owner
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A loose or dirty connection on the black wire that runs from the -side of the coil up through the distributor and connects to the points plate under the dist cap can also cause those symptoms. I have had two that the black wire became loose at the coil and those things happened. Make sure that black wire isn't up against the ignition shielding where it could have a bare spot and touching intermittently.
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Thread Starter
Team Owner
Joined: Mar 2003
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From: Wilmington N C
St. Jude Donor '14 thru '26
A loose or dirty connection on the black wire that runs from the -side of the coil up through the distributor and connects to the points plate under the dist cap can also cause those symptoms. I have had two that the black wire became loose at the coil and those things happened. Make sure that black wire isn't up against the ignition shielding where it could have a bare spot and touching intermittently.
Team Owner
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From: Kannapolis NC
When I first got my 60 (same ignition setup), I had your symptoms intermittently. Every time I took the distributor cap off to check things it would run fine for weeks. Then it would start to buck and die again at random times. I decided to put in an SE Breakerless system and while I was installing I moved the black wire on the negative side of the coil and it pulled out of the connector. Checking the end of the black wire strands, they were corroded (sort of burnt looking). I cut a half inch off the wire and recrimped the connector that goes to the coil post and it has been several years now with no issue. Either end of the black wire can cause this, it's what provides the ground for the coil when the points close to create the spark. Pretty important for such a simple wire.
Burning Brakes
Joined: Aug 2021
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From: NH
In my 62 I had a similar problem after hitting a huge pot hole. It was so bad, I thought I had broken something in the front end. Front end was fine, but then I started having the studder type problem you have. Long story short - the jolt had loosened the crimp on the red wire from the ballast resistor to the coil. Put on a new crimp - problem solved.
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From: Wilmington N C
St. Jude Donor '14 thru '26
Update for anyone who cares: I told my mechanic about the noise and feeling of the ride (I don't do points/condenser anymore due to my arthritic hands) and told him of my suspicions of the points/condenser, and so he changed them, set the dwell and timing, and pulled the plugs to see how they looked {looked okay, but had a small amount of carbon build up, which he cleaned off}. He didn't take it out for a test ride. When the car was pulled out into the parking lot, right away I could hear a deeper rumble, sort of like a Harley Davidson motorcycle has, and a noise like it was about to stall out. However, I didn't say anything, as I wanted to take it home and see how it sounded and ran. It ran fine and never did stall, but I'm not satisfied that whatever was needing attention before still does. His only other suggestion was to replace the Holley carburetor. I'm not interested in making that change. My "plan" is to drive it some more and see what develops. I guess I'll also adjust the mixture a little on the carb to see if that improves it at all. His other suggestion was to really jump on it to get the carb & plugs cleaned. I don't normally drive that way, but I'll try that too.
His other suggestion was to really jump on it to get the carb & plugs cleaned. I don't normally drive that way, but I'll try that too.
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When the car was pulled out into the parking lot, right away I could hear a deeper rumble, sort of like a Harley Davidson motorcycle has, and a noise like it was about to stall out. However, I didn't say anything, as I wanted to take it home and see how it sounded and ran. It ran fine and never did stall, but I'm not satisfied that whatever was needing attention before still does. His only other suggestion was to replace the Holley carburetor. I'm not interested in making that change.
"About to stall out" sounds like it may not be idling high enough. Before messing with mixture screws, make sure that's at the appropriate setting, especially since your plugs looked OK. (I'd not change mixture without a vacuum gauge.)
Why did you say "whatever was needing attention before still does"? Wasn't the issue a cough or sputter when driving which it doesn't appear to have any longer?
Melting Slicks
Joined: Sep 2005
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From: Warminster PA
Update for anyone who cares: I told my mechanic about the noise and feeling of the ride (I don't do points/condenser anymore due to my arthritic hands) and told him of my suspicions of the points/condenser, and so he changed them, set the dwell and timing, and pulled the plugs to see how they looked {looked okay, but had a small amount of carbon build up, which he cleaned off}. He didn't take it out for a test ride. When the car was pulled out into the parking lot, right away I could hear a deeper rumble, sort of like a Harley Davidson motorcycle has, and a noise like it was about to stall out. However, I didn't say anything, as I wanted to take it home and see how it sounded and ran. It ran fine and never did stall, but I'm not satisfied that whatever was needing attention before still does. His only other suggestion was to replace the Holley carburetor. I'm not interested in making that change. My "plan" is to drive it some more and see what develops. I guess I'll also adjust the mixture a little on the carb to see if that improves it at all. His other suggestion was to really jump on it to get the carb & plugs cleaned. I don't normally drive that way, but I'll try that too.
His other suggestion was to really jump on it to get the carb & plugs cleaned. I don't normally drive that way, but I'll try that too. Maybe look for another shop - did a quick google search for Corvette shops in Wilmington NC (location in your profile) and found Rackleys, they seem to show several Corvettes on their web page. I have no knowledge of their ability so do your own due diligence before committing. Hopefully they weren't the shop you used...........
http://rackleysperformanceandauto.co...mance-gallery/
Thread Starter
Team Owner
Joined: Mar 2003
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From: Wilmington N C
St. Jude Donor '14 thru '26
How can you not test drive a car after working on it to see if the customers concerns have been addressed?
Maybe look for another shop - did a quick google search for Corvette shops in Wilmington NC (location in your profile) and found Rackleys, they seem to show several Corvettes on their web page. I have no knowledge of their ability so do your own due diligence before committing. Hopefully they weren't the shop you used...........
http://rackleysperformanceandauto.co...mance-gallery/
Maybe look for another shop - did a quick google search for Corvette shops in Wilmington NC (location in your profile) and found Rackleys, they seem to show several Corvettes on their web page. I have no knowledge of their ability so do your own due diligence before committing. Hopefully they weren't the shop you used...........
http://rackleysperformanceandauto.co...mance-gallery/
Thread Starter
Team Owner
Joined: Mar 2003
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From: Wilmington N C
St. Jude Donor '14 thru '26
Arrrgh: the mantra of today's mechanic. No rebuild, no tune and test, just replace. I'm wondering just how much your mechanic knows and understands carburetors.
"About to stall out" sounds like it may not be idling high enough. Before messing with mixture screws, make sure that's at the appropriate setting, especially since your plugs looked OK. (I'd not change mixture without a vacuum gauge.)
Why did you say "whatever was needing attention before still does"? Wasn't the issue a cough or sputter when driving which it doesn't appear to have any longer?
"About to stall out" sounds like it may not be idling high enough. Before messing with mixture screws, make sure that's at the appropriate setting, especially since your plugs looked OK. (I'd not change mixture without a vacuum gauge.)
Why did you say "whatever was needing attention before still does"? Wasn't the issue a cough or sputter when driving which it doesn't appear to have any longer?
Le Mans Master
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From: Richardson Texas
If you feel comfortable enough that the car won't leave you stranded by the side of the road, get it out on the highway and run it for at least 30 miles at 65-70MPH. It's what we used to call a "Poor Man's" tune-up. Putt-putting these old cars around is not in their best interest...they need to be blown out every once and awhile. You're not going to hurt it.
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He may have set initial timing per the old manuals which are generally pretty conservative (retarded). I would check the timing and see if you can boost it several degrees without getting combined initial and centrifugal timing over 36 degrees which is typically a pretty good number for most engines. Low timing could make the engine feel weak-kneed at low rpm.
Thread Starter
Team Owner
Joined: Mar 2003
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From: Wilmington N C
St. Jude Donor '14 thru '26
If you feel comfortable enough that the car won't leave you stranded by the side of the road, get it out on the highway and run it for at least 30 miles at 65-70MPH. It's what we used to call a "Poor Man's" tune-up. Putt-putting these old cars around is not in their best interest...they need to be blown out every once and awhile. You're not going to hurt it.
Thanks for all the suggestions. I appreciate them.