I have '73 240z and recently purchased a pair of roundtop 4 screw carbs. I also got the throttle linkage for my carbs. I noticed that the carbs don't seem to have a spring that makes the butterflys close when there is no pressure applied to the throttle linkage (unlike my flattops which have that). When I start my car the butterflys open up on their own. I think that there is suppose to be a spring so that my car doesn't throttle by itself. Am I right? If not, what's wrong?

Also, if I push on the gas pedal, it will stay at the point where I stopped pushing. Making it dangerous to drive, since I would have to pull up on the pedal to decelerate. I think that if my spring idea is right, then it will take care of this problem too.

Thanks

well, under the hood of my '73, there's a spring in the center of the engine compartment toward the rear after the first section of the throttle linkage. this is what makes the gas pedal go back on mine (i think). the carb does have light springs, but nothing that would return enough pressure to raise the pedal. hope this helps some!

Should be a spring that connects to the exhaust heat shield just in front to the rear carb. If you still have the heat shield in place look for the hook on it and that's where to connect your return spring.

And a throttle that won't return definately makes it too dangerous to drive.

The butterflys open up because your springs are obviously not there so simple air pressure is doing that. Like 2Many said on the heat shield there should be two hooks, this is where the throttle return springs are anchored. You can get these from Motor Sport Auto www.Zcarparts.com or ZTherapy www.ztherapy.com. Hey if you get desperate i have an extra set you can have for free. I live in San Diego.

i have installed SU's on both my 73 & 74. Neither had a spot on the heat shield to attatch the springs to. I just drilled & stuck in 2 sheet metal screws into the shield, and attatched the springs.

A thing to remember- find the springs you're going to use first, so you have an approximate length- THEN drill a spot to attatch them (ask me how i know:rolleyes: ) It really is a simple job.

HTH, Jeremiah

Don't start your car behind a Pinto!

steve77