I have an 84 L69. I removed all of the computer stuff. The last to go was the carb. I've replaced it with a Qjet from a 73 chevy, it's a 650 cfm.

Everything seems to be fine, except for the fact that the throttle return spring isn't near strong enough. I've purchase two very strong springs and put them on. One goes in the place of the original, pulling from the bottom side of the linkage towards the back of the car. That wasn't strong enough to return it so it was resting on the idle screw.

I hooked up a second from the top pulling forward, now there's enough to bring it all of the way down.

My question is this: Why is it this difficult? Before installation, it everything worked smoothly and easily. Now the pedal is very stiff of course with that extra tension.

What can I do?

Thanks for your help.

 

sounds like you are not using throttle return springs for that application.
Springs all have different tension and uncoil rates.
They make special springs just to use as throttle returns and they have been working great for years. The rate on those springs stays pretty much the same and is not too stiff on the pedal. To tighten up the throttle-closed position, you simply shorten the straight (uncoiled) part of the spring until it pulls the throttle lever tightly.