What i remember from a 260z driver in the neighborhood.. the flattop needed a lot of tuning..  After a few weeks the idle was AGAIN to high.. they were sick and tired of them..

I never took a set (on my attic!) apart..  i bought them years ago cheap just to see what kind of trouble makers they are.. My view so far.. they are made to complicated.

I don’t recall a lot of tuning being required, my 260 would constantly sputter to a stop whenever it got hot during the summer. It would restart after a brief cool down, and then act up again.

Tried multiple fixes (added 2nd electric pump instead of mechanical one, wrapped all fuel lines, ran copper fuel line in front of radiator) all to no avail. To date, the worst car I ever owned.

3 hours ago, bluez said:

I don’t recall a lot of tuning being required

My 73 held its tune very well too. The dealer did all the stuff to remedy the vapor lock in the summer and if it helped it was minimal. I can remember many days on the way home from work popping the hood latch to improve airflow in the engine bay which did help. 

When I bought my 73 in 1979 the dealer mods to correct vapor lock had already been installed, including the "competition hood". I did not know anything about this until the internet came along. The car ran well and kept its tune. It wasn't until it was about 35 years old before it started with the vapor lock problem. Years later I swapped to rebuilt round tops. I think the flat tops were just worn out, no different at that age than round tops.

Isn't there a thread on the Flat Top induction system? I seem to remember writing a bit about my experiences as a Datsun dealer mechanic during that time.

On 3/2/2024 at 7:15 AM, dutchzcarguy said:

What i remember from a 260z driver in the neighborhood.. the flattop needed a lot of tuning..  After a few weeks the idle was AGAIN to high.. they were sick and tired of them..

I never took a set (on my attic!) apart..  i bought them years ago cheap just to see what kind of trouble makers they are.. My view so far.. they are made to complicated.

Unless it was a North American spec car, that was a different carburetor.

On 3/1/2024 at 8:14 PM, DC871F said:

Not familiar with his work on them. I was to understand that there were no adjustments to get them tuned correctly. They either ran really good at operating temp, but suffered hard starting, or they ran terrible but was easy to start.

 

On 3/1/2024 at 9:27 PM, Patcon said:

I'm not totally sure, but I think there are actually a bunch of adjustments available on flat tops which is what makes them hard to get tuned properly.

The directions for tuning/adjusting are in the EF section of the FSM.

48 minutes ago, SteveJ said:

 

The directions for tuning/adjusting are in the EF section of the FSM.

Good idea to also have the 73/74 Fuel System Modifications Plus manual.

What isn't mentioned in these recent observations is that the complete induction system - from the cylinder head out - was changed for the 73 model year. The carbs are one component of the complete system.

Yes, there is a official service anouncement made in 1973 that the 1973 240z engine L24 had a different head as the pistons go ABOVE the deck! Watch out for this, it's just a small part of a mm but they go above the deck!

 

Those flat tops remind me on the emission carbs i am working on with the scooters: 

 

 

3 minutes ago, bartsscooterservice said:

Those flat tops remind me on the emission carbs i am working on with the scooters: 

Yeah, IN THE BIN!  But Maybe one day they will suddenly be in high demand.. until that day...