Datsun Roadster Forum-311s.org

Any chance there is a problem with the dashpot springs? I've never seen them break, but if you are saying that changing the dashpot oil made that much of a difference, then perhaps one or both of of the carb pistons are rising too quickly.

My 1600 had something like this , I found the su slides were free lifting , but the back one caught going down temperarily

Ever since I replaced the head and gasket late last year, I have experienced surging when applying light throttle. I kind of gave up working on it last spring. While talking to the Wonderful Dave Firestone recently, luckily he lives close by, the issue came up and he gave me some ideas. I talked to the equally Wonderful Ted Heaton who had some spare throttle return springs to try. DEF for the win. I replaced the springs and the issue seems to be gone. I have only driven a few mile but it never surged.

Seems the springs were replaced with weaker ones by someone before me. I don’t know why this has worked for 6 years. Maybe I stretched them a little during the head replacement. The Ted springs apply 4X the tension.

Longer stock Ted spring and one from the car-
The two weak springs that were on the car are also different-
A very BIG thank you to Dave and Ted for helping me solve this issue.

I have to add that rwmann in Port Washington, NY was close with his broken throttle return spring guess.

Also thanks to everyone for their suggestions. I always thought it would be something simple when I found the solution.

A guess based on a similar, personal experience, RB!