Fuel recommendation for a '73 240z with rebuilt engine and SU carbs?

[Dadsun]

My Z seems to be running rich. I have swapped in the SU rebuilt carb set and adjusted as best I know how with the unisyn tool and mixer adjustment on the bottom. 

[Yarb]

Need a lot more info than what you have given. Pics, source of where the carbs were sourced etc. Anything you can add is helpful. Reasoning for replacing them etc etc.

[w3wilkes]

On the question of the thread title... When I had my carbs done by ZTherapy I did the tank and all rubber lines with new Gates hose rated for E85 if we're ever forced to go that way. Since I did the whole fuel supply front to back I've run nothing but ethanol free fuel which is readily available here in Utah. The car seems to be very happy with the ethanol free fuel.

[Dadsun]

Yeah, apologies for the sparse info.  Here's a thread on my conversion to the Paltech refurbished carbs.

This was to replace the original flat tops which were sorely neglected and of course problematic. 

 

[Dadsun]

Here's a pic from the last time I was adjusting them. Notice that I'm running coolant through the intake manifold. Some choose not to do this, right?

[Dadsun]

Since then I've swapped in the fuel rails to go with the round tops. I run 91 octane because it's the only ethanol free gas around here. 

[Patcon]

How many turns down are the mixture nuts?

Are you sure its rich?

Is the float fuel level correct?

[siteunseen]

I put a few gallons a year in my '72, it's 93 with 10% ethanol.

To be honest the most problems I've read on here is a result of low fuel chambers.

Get the floats right then you can adjust the carbs & timing correct. I tried and tried for a month then went to basics like my Dad taught me, now it's rock solid.

 

[DatsunZGuy]

Older cars without catalytic converters are not going to burn newer fuel as efficiently.  In fact, one of the main jobs of the catalytic converter is to change hydrogen sulfide into sulfur dioxide, which has no odor.

I just returned from a local cars and coffee event and pretty much every car older than 1980 smelled like it was running rich while driving past.  The bottom line is our Z cars will seem to run rich when compared to their newer contemporaries .  Better to run it bit rich than going too lean and risk engine damage.  IMHO

   

[Dadsun]

Thanks for the info on the float level. I will take a look. And also will have to refresh my memory on the mixture nuts turns. I'm pretty sure I wound up settling exactly halfway between all in and all out. I had bought and used the mixture tester that uses color.of the flame via spark plug port, but that seemed to work only once. Since then it shows a yellow flame no matter what I do. 

Back to the subject topic briefly: I have access near my house to both non ethanol 91 and 87 octane. Should I go with 87?

[w3wilkes]

I've used 91 non-ethanol and 88 non-ethanol. Can't tell the difference, they both run great. My altitude is pretty much 4,500 ft. and above.

Edited May 4, 2023 by w3wilkes

[SteveJ]

16 hours ago, Dadsun said:

Thanks for the info on the float level. I will take a look. And also will have to refresh my memory on the mixture nuts turns. I'm pretty sure I wound up settling exactly halfway between all in and all out. I had bought and used the mixture tester that uses color.of the flame via spark plug port, but that seemed to work only once. Since then it shows a yellow flame no matter what I do. 

Back to the subject topic briefly: I have access near my house to both non ethanol 91 and 87 octane. Should I go with 87?

Stock motor with stock compression - go with 87 or choose 91 if you like to burn money for no gain.

If you have higher compression, go with 91.