240z SU Carb Tuning?

[Triple G'Z]

I currently own a 71 240z and am building two motors. I have an 2.8L that is completely stripped down and ready for rebuild. I also own a complete VG30ET. I really want to keep the 2.8L but have concerns with tuning the SU Carbs on a regular basis versus just implementing the Fuel Injected VG. Does anyone live in the New England Area where the temperature and humidity can change hourly? If so, how does this affect your carb equipped motors? How much tuning is needed on a regular basis to make the motor run right. I understand that Carb motors need more attention than f.i motors but i want to enjoy driving the car without the hassle of needing to tune it every time i turn the key.

Any help or advise would be appreciated!

Thanks

[Bruce Palmer]

When it comes to tuning SUs the major contributor to ease of tuning is to take the carbs back to square one. Once renewed, they are the easiest carbs in the world to keep up with. I tweak mine twice a year, once in the spring when the weather changes and once in the fall when the weather changes. This is on a year round driver. Once tuned they hold tune.

A worn out set of SUs can be tuned and will hold tune for about 13 milliseconds....

If you want some real meat and potatoes info, buy the JUST SUs DVD and study up. Takes all the mystery out of it as far as I'm concerned.

[Arne]

I don't even tune mine that often. Set 'em and forget 'em. SUs are velocity-sensing carbs, so they tend to compensate for changing conditions on their own. I'm a firm believer that most SU problems are CAUSED by people re-adjusting them when it's not needed.

[Gary in NJ]

I'm a firm believer that most SU problems are CAUSED by people re-adjusting them when it's not needed.

But adjusting SU's is just plain fun (seriously). I just enjoy tinkering with these mechanical marvels.

[Triple G'Z]

Thanks! Have you noticed any difference or was any different tuning needed for the new unleaded gas/ ethenol mixture at gas stations these days? I will definetly look for that SU DVD. Does anyone sell SU Carb rebuild kits to bring those back into shape? Thanks again for your help!

[erectorset]

My 1971 240Z has been in Boston since 1974. I am the original owner and other than topping off the carb fluid I have never touched the carbs except to re-adjust idling speed after tune ups which are now very infrequent because I do not dirve the car very much and only when it is sunny. They work fine and the car starts up every year after sitting through the winter for five months. In reading the numerous posts about carb refurbishing I am always left wondering if the car would run smoother if I did refurbish the carbs. I will need to find someone to do it for me however as I am not a mechanic. Trying to find mechanics in Boston with Zcar experience is not easy as the cars are pretty much extinct in this area.

[Gary in NJ]

Does anyone sell SU Carb rebuild kits to bring those back into shape?

www.ztherapy.com

[Arne]

Have you noticed any difference or was any different tuning needed for the new unleaded gas/ ethenol mixture at gas stations these days?

Oregon is exclusively E10 for the past couple of years. I noticed no difference when that change was firmed up.

[erectorset]

I always use the highest octane gas available and add lead additive to every other fill up since lead was removed from gasoline.

[Bruce Palmer]

Oregon is exclusively E10 for the past couple of years. I noticed no difference when that change was firmed up.

Several years ago, back when we could still source real gas in outlying areas of Oregon, I made an LA and back trip which allowed 3 tanks of Oregon gas and the rest California oxygenated stuff. Docummented mileages on both showed a 20% reduction in mileage with the oxygenated crap. All in all, the economics of the stuff we have to pay to grow, etc. etc. etc. coupled with the fact that it takes 20% more to do the same amount of work, I fail to see any benefit. But then it's good for the farmers and drives the price of corn up so our other food items cost more.........

[mlc240z]

My 1971 240Z has been in Boston since 1974. I am the original owner and other than topping off the carb fluid I have never touched the carbs except to re-adjust idling speed after tune ups which are now very infrequent because I do not dirve the car very much and only when it is sunny. They work fine and the car starts up every year after sitting through the winter for five months. In reading the numerous posts about carb refurbishing I am always left wondering if the car would run smoother if I did refurbish the carbs. I will need to find someone to do it for me however as I am not a mechanic. Trying to find mechanics in Boston with Zcar experience is not easy as the cars are pretty much extinct in this area.

Bite the bullet and send them here for a refurb. You won't regret it.

www.ztherapy.com

After 39 years as an original owner, you only think they run good.

When you get them back, they will be better than new.

Absolutely amazing!

[tlorber]

I'll pile on here and say that SU's are really easy to set up and keep going once you understand them-set it and forget it. The only reason I would even consider fuel injection is that (at least with modern systems) you can map the afr at each rpm to run exactly the mixture the motor wants. With SU's you are at the mercy of the needle profile. For most of us here they are perfectly adequate.