I am pretty determined to keep my newly acquired '73 240Z original and run the flat tops (AKA boat anchors).

Initially, the car idled real well but coughed all the way up the power band. With a little study on the threads here, it sounded like the issue was the small pump on the side of the carbs. Sure enough, took these both apart and cleaned out the 'jelly' in the forward carb and the operation was much improved. (The rear carb side pump looked to be in good shape). Float bowls were both at the proper levels.

The car now idles beautifully, works well when accelerating hard, works well when choked; but seems to have an intermittent miss when running at constant freeway speed. It 'feels' like the car is running lean. So, I am thinking that I will adjust the needles 'up' about .010" and see if that solves the problem.

Any thoghts on this from the flat top crowd? Any input, other than switching to SU (which I agree are better), is appreciated

Thanks,

Rich

OK, running lean was exactly the problem. I pulled the flat tops off and checked the piston and needle configuration. The collar of the needle was about .010 out of the piston base on both carbs. I loosened the set screws and made the collar flush with the base, then re-assembled. Car now runs very smooth at constant speed.

We will see how these perform now over the next couple months.

The hot ticket back in the day, was to remove the weight attached the underside of the piston for faster throttle response.

Sounds like a good idea. I'll have to give that a try.

hmmm, I thought only the 260z's had flat tops.

hmmm, I thought only the 260z's had flat tops.

Nope, they were stock on the 73 240Z.

Glad to see that you have retained them and kept the car original.

Generally, after a strip down and service they once again perform as new.

Nope, they were stock on the 73 240Z.

Oh, I learn something on this forum every time I log on.

Hey Rich !!! They didn't make that V3 kit for nothing. Just wait until it gets hot this summer!

Bob

Hey Rich !!! They didn't make that V3 kit for nothing. Just wait until it gets hot this summer!

Bob

I read somewhere that if you open up the hole on the back of the fuel rail return line that it solves alot of the problems. Guess I will have to see how it does. As for now, I am very happy with how they are running. If I didn't pop the hood, you would think there were SU's under there.

Any input, other than switching to SU (which I agree are better), is appreciated

I read somewhere that if you open up the hole on the back of the fuel rail return line that it solves alot of the problems. Guess I will have to see how it does. As for now, I am very happy with how they are running. If I didn't pop the hood, you would think there were SU's under there.

Not to nitpick, but the flat tops are still SU's. Hope they work out this summer!

Edited February 26, 201015 yr by JonnyRock

Rich,

I'm just giving you a hard time. Seriously, I hope they work out for you. Must say I'm impressed that you got them to work so well. You might become the board expert on flat tops if you're not careful!