L24 troubles

[jezze]

Well my stock '71Z is still running funny. The car seems to idle fine, but when I'm on the freeway at normal speed it will repeadedly backfire through the one of the carbs. When I floor it it will run well up to about 4000, then feels like it's running out of gas or the points are whacked. Also I checked the plugs and they are all kind of white, the 4,5,6 being the worst with a slight flakyness to them. I've replaced the wires, plugs, points, cap and rotor.

I thought I ajusted the carbs well, but maybe I didn't? Any thoughts or comments to something I may be overlooking? Thank ya'll

[Arne]

White plug indicate that it's running lean, and the backfire and loss of power at top can also indicate that. Since the rear plugs are whiter than the front, I'd guess that there is something wrong with the rear carb. Low float level, way whacked mixture setting, needle came loose and fell into the nozzle, stuck piston, ???

Anyway, it looks to me as thought the rear carb is rear you should start hunting.

[jezze]

I am using 7mm wires, champion plugs and points from a corporate auto-parts dealer. Could this combo result in a poor performance at higher RPM's? Are these z cars fairly tempormental compared to chevy's for example? I had a 1969 Camaro and it seemed that enigine would run no matter how I neglected it.

Is it possible for these cheap parts to allow popping through the carbs, and hesitation above 4Grand?

[Mat M]

Hey, Jesse.

I agree completely with what Arne stated in his last post.

I wouldn't worry about the wires, but the plugs may be suspect. NGKs are your best bet.

What sort of ignition are you using? Worn points may be a place to look, as well.

[edit] I just had a horrible bout with my carbs, but using Arne's, JMortensen's and EScanlon's advice steered me in the right direction!!

[Arne]

I am using 7mm wires, champion plugs and points from a corporate auto-parts dealer. Could this combo result in a poor performance at higher RPM's? Are these z cars fairly tempormental compared to chevy's for example? I had a 1969 Camaro and it seemed that enigine would run no matter how I neglected it.

Is it possible for these cheap parts to allow popping through the carbs, and hesitation above 4Grand?

No. What you are describing is not ignition related. It is in the fuel delivery.

That said, I personally despise Champion plugs, and would throw them far, far away. Most Nissan/Datsun people use NGK for good reason - they work. But the plugs aren't your problem right now.

[kenz240z]

You might also want to check for vacuum leaks around the rear carb. Start the car and spray a little carb cleaner around the rear intake, carb gasket, throttle bushings, etc... If the engine runs rougher for a moment when you spray one of these areas it is leaking air. The leaking air will cause the mixture to be leaner.