Maybe an ignition issue? 77 Carb car

Ok. Sorry for yet another post. Hate to bother but everyone is super helpful. So after my last post I think I have ruled out a fuel issue with my car but now I’m leaning towards ignition. So this is what is happening. I can start the car in the garage and let it run as long as I want getting even the oil all the way to temp and when warm and parked it will freely rev all the way past 6k without any issues. However as soon as I try to drive the car, within about a mile it will fall on its face and die. But even after this I can take it home, start it and let it run in the garage again with no issues. I checked fuel pressure after it died and it was fine now at about 4.5 PSI. In terms of ignition, it has all new plugs and extenders, new pertronix flame thrower coils and has been converted from points to a pertroix unit. I have checked timing and at idle I show 10 degrees at both banks and 35 degrees at 5k. One thing I’m starting to think is possibly the alternator. The charge light doesn’t come on but at idle with the lights and fans on I only see 12.5 volts. It’s 13.6 with everything off. Would the ignition pull more power under load? If so do you think my alternator might be the culprit? Or possibly something else? I find it so weird that it runs so beautifully in the garage all the way up the rev range but dies under load.


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Thanks! I had seen your post. I’m glad you got yours straightened out. I checked the timing on each bank with the timing light and they both seemed to fall in line. Thee we strange thing was after the car died today, I was able to restart it and take it past 7k in the first three gears then it acted like it ran out of gas and died. But before that it pulled clean and hard. That’s why I was originally thinking it was a fuel issue but I ran out of places to look there.


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Thanks. When it dies the tach follows the engine rpm and the generator light then illuminates. When I checked voltage, I did so at the battery. I’ve never seen it get as high as 14v at any time.


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When it dies, I have checked voltage at the coils and there is indeed still voltage there. It restarts after it dies but it will die again. Each time it will run less time and become harder to restart


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Thanks! I do indeed have the Birdman fuse blocks in place. The Pertronix unit in the distributor also has its only dedicated line directly back to the fuse block as well to try to prevent it having any voltage fluctuation or noise issues. I’m starting to think it may be a fuel issue. I had emailed Hardi, the manufacturer of my new fuel pump and the recommended I try removing the fuel filter to see if I’m having a fuel flow issue. I may try that this weekend


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Thanks. Interesting thoughts. When it dies it doesn’t immediately shut off. It stumbles and if you feather the throttle you can keep it going for a bit before it does out. When it restarts, it will usually run bogged down with little power. If I was experiencing a transistor failure could it behave like this, or would it be a more of an on and off light switch scenario with the ignition?


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Interesting thought indeed. I’m going to check my fuel filter first this weekend but if it’s fine I may just pull the Pertronix out. I have a new set of points on the shelf and the original coils. So I may just put all that back in and retime it and see what happens. The pertronix is less than two years old with maybe 40 miles on it. I threw it in early in my restoration journey. Crazy thing is it will run fine all day not under load. You can leave it in the garage let the oil get to full temp and it will idle and rev freely all the way through the rev range. I thought I was making it a bit more reliable with the pertronix but points just work. I guess that’s why they were around so long.


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Interesting thought. The pertronix is indeed just a replacement for the points. The tach is still wired and operating the same way at the coil. So if my tach follows the engine revs on the way down and doesn’t just drop, would that suggest my coil is still firing and thus the pertronix must be working?


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Sorry for the long delay. Turns out I solved the issue and it was indeed fuel related and not ignition. So I had rebuilt the entire fuel system as part of my restoration. New lines, filter, rebuilt carbs, new pump, and a new strainer in the tank. As I could not find the original style strainer, I bought a generic one in the attached picture. Well it turns out there was a rubber grommet on it the holds it onto the outlet pipe and the grommet fell apart. Half of it was left inside the strainer and this whenever there was suction on the outlet, the piece of rubber was packed against the pipe and blocked fuel. I figured this out when I took the line off of the tank with a quarter tank of fuel and gas barely dripped out. I removed the strainer and the car ran beautifully. I decided not to install another one as it is only about 3-4 inches of fuel line between the tank and the filter and I don’t plan to drop any rocks or large debris in my tank that would clog that short distance. So a word of caution on trying to adapt parts to replace ones that are no longer available. Sometimes it works great and other times you bang your head against the wall for months on a dumb problem that you yourself created. That being said if anyone knows of a good tank strainer replacement for a carb car let me know. It looked like the one for the Porsche 928 and 944 was similar but it’s like $80 and there’s no way to tell if the threads are correct without buying one. Thank everyone for all of the help!
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