I am having an issue with our '69 1600. The whole car will start lurching/bucking/surging after the transition from light or no throttle to very slight acceleration in 1st or 2nd gear. When I let off the gas coming down my street then turn into the driveway and roll into the gas to start the climb it will lurch so bad that it starts chirping the tires. That is the worst case and requires either full throttle or stop and try again. It makes low speed light throttle driving very difficult. It's as if the pistons in the SUs are flopping up and down without any damping.
This behavior started a couple months ago but seems to be getting worst. I have checked the carb tuning, float level, checked the timing and have played with the mixture. I used ATF in the pistons, I tried straight 30W to slow things down and I have tried driving without the plungers in the pistons. It performs the same in all three cases.
As I am writing this I remembered the electric fuel pump was changed but to a new one that was supposed to have the specs. as the one that has been in the car for ten years. Maybe I'll switch it back as it is the only thing I can think of at this point.
Just maybe it is spark not fuel.
Run the engine in the dark and look for any lightning display.
Check the points, if you have points, for correct gap and function.
As the saying goes, when your sure it is a fuel problem check the ignition and vice versa
i had a very similar problem years ago - it was caused by the little graphite button on the center contact (coil voltage contact) in the distributor cap had broke and fallen out so the coil voltage to the rotor was through the spring and spark was intermittent but car would run, but not well. (so spark was the problem). Not sure how the button broke - found pieces of it inside the distributor.
You are in need of the old sun machine oscilloscope
Are the carb pistons slides moving smooth and free when you push them up ....maybe one is froze and your running on 1 carb
A spark plugs fuel fowled , or a plug wire arcing very possible too....carbon tracking in distr.
Check for vacuum leak , ign timing cetrifical adv
Last edited by redroadster on Mon Apr 12, 2021 6:17 pm, edited 5 times in total.
I would agree that on and off, lurching etc suggests more of an electrical issue than carbs. Usually if it's lean it will backfire through the carbs, and an overly rich condition will just make it boggy and slow.
A quick check of the points wire might be in order. The wire likes to break inside the covering and could be intermittently making a connection during timing advance. I have also had a brand new rotor with leak path to the distributor shaft causing an intermittent spark short.
Hope that helps.
Thats not a R16 death rattle....its a dried leaf hitting my heater blower fan.
1968 SPL311 non-smog