Are early SU's better?

[car_dumi]

I've been visiting many websites and seen many people talk about switching out their carbs and replacing them with older ones. Is this a common practice? What are the advantages/ disadvantages? What would it cost? Is there a cut-off on the years (ex. up to 76 the carbs are good but after that they're crap) Should an individual with severe income limitations such as myself even consider this?

Sorry about all the questions. Any help would be greatly appreciated.

Thanks

Can anyone tell me what is happening in this picture?

[toddz240]

You didn't mention which carbs you currently have or what the problem is.

It is common to replace the "flat top" SU's with the earlier "round top" ones. The earlier (70-73) were not encumbered so much with pollution stuff and are easier to work on and provide better power. Once you get to '74( the 260Z carbs) look out. Some people have had success with them but the earlier ones are better.

It's not difficult to switch but you need all the pieces (ie: linkages etc). If you are considering doing this you will want to find a good set of used early carbs (or buy a set outright from Z Therapy). Finding a good set will take time and cost a couple hundred bucks and may still require some TLC to get them right. Buying a set from ZTherapy will cost $500+ but they are a work of art and are set up beautifully (and come with a training video to help you install and adjust them)

Post any questions you have to this forum or to the IZCC forum (check out www.zhome.com) What you're thinking of doing has been done plenty'o' times with great success.

Todd

[car_dumi]

sorry bout the lack of info but I don't really know what I have. I have a '73 and assume everything is stock.

I thought I read somewhere that the pollution laws came into effect something like mid-1972 and that the '73 carbs were especially bad due to the fact that they had just started making them.

I realize that this is in every Z-car forum like a million times but its hard to find answers to specific questions... and I'm lazy.

[Royce]

First you have to identify what you have! It's been a long day, but I'll give it a shot! Pop the hood and look at the carbs. All the Z carbs have a large, approx. 4" diameter, cylinders that sit vertically on top of each carb with a plastic nob that unscrews. Originally the '73 240 and 260 cars came with carbs where the cylinders have flat tops, looks like a soup can. On the earlier 240s the carbs looked very similar but instead of a flat top the tops are more dome, or bell, shaped. All the 280s originally came with fuel injection so they don't typically apply here but you never know someone may have added SU's, I've thought about it myself and I have heard other have done it.

The '70 & '71 carbs are the same. The '72 carbs are slightly different but for this discussion we will consider them the same. Todd was right that there are people who have made the flat tops work well! He also made a good suggestion referring you to ZTherapy. I suggest you check out there site at www.ztherapy.com for better instructions regarding identifying SU's. They are the tops on my list and would love to have them rebuild my SU's. I am very impressed by there enginered solutions to some of the problems common to the early Z SU's.

There is lots of talk on this web site and pretty much every web site. I have talked to Dave Rebello, Rebello Racing, and Scott former owner of ZTherapy and SU expert. Both of them claim they can make the SU perform every bit as good as Nissan fuel injection, Weber's, Makuni's, etc, etc. even on a bored/stroked 3.2 liter L6. So I would say the key is pick the type of fuel delivery you like, find someone who knows how to do it right, and go to it. The thing I like about the SU's is that they are light, I already have them, and I can easily service them. Sure I like the look of the triple weber setup but it is a lot of cash and would require me to learn something new! I personally have already invested the time into the SU's and would rather spend future time learning how to rebuild a trans instead of a different set of carbs. But hey, I reserve the right to change my mind in the future.

I currently have both a '73 240 Z and a '75 260 that have both been changed by previous owners to '72 240 carbs. I would say it is a simple swap but you will need to learn about tuning the carbs or have someone else tune them once they are installed. Also, you will need the throttle linkage and the air cleaner for the early type carbs. It can start adding up quick but they are out there.

Questions and corrections are welcomed!

Have fun!

[car_dumi]

thanks a lot.

i appreciate the help and will get back to you as soon as I can investigate further

[EScanlon]

Just be aware that in California you still have to comply with whatever smog laws were in effect for the year car you have. A 73 definitely had the smog pump and other doodad's. Although you can do the carb swap, and only a Z enthusiast would know the difference, you still have to pass the emissions test.

When you mention severe income limitations, I would probably suggest you get the car tuned up and working well with what equipment you currently have. Wait till your budget is not so tight before getting into buying and getting equipment that may be a visual or a performance enhancement to the car.

Get the mechanicals done first. The brakes, the engine, the shocks, bushings, etc. are all items that will add TONS to your enjoyment of the car, and you won't yet be into the hundreds of dollars to make something work.

In a nutshell, if the car is performing poorly and other problems then by all means, go for the carbs. But like most older cars there are quite a few items that you can address just to keep them on the road. If the car on the other hand is running, then invest money in a good thorough tune-up. Get the valves adjusted. Flush out the radiator and refill it with clean new anti-freeze. (I know you're in California, but anti-freeze also makes the coolant work better as well as having lubricants that are good for the pump as well as avoiding corrosion inside the block). Get the oil system purged and cleaned, and replace with a good synthetic oil or your favorite oil. Address the brakes, get the pads checked, turn the rotors / drums if needed. All in all make sure that the periodic maintenance the car SHOULD have had, is brought current and correct. THEN look into modifying and changing the equipment on the car.

In the long run, you will have spent LESS doing it this way. There are many people who start modifying something WITHOUT knowing whether the car is working well. Then when they can't get the mod to work, have to back track in order to get the car working, OR they end up paying a mechanic big bucks in order to make it work.

Remember, this is part of the learning curve.

[beandip]

If you have flat top carbs my best advise is to replace them as soon as you can . I just bought a set air cleaner carbs and linkage $190.00 and have another set I got for a friend just the carbs $75.00 the next thing to look at is the ignition get one from a '79 zx and get it all the dist and its mount and the coil. it has a module on the side of the dist. marked 12 80 that is the one to get. The thing that was brought up about cal and emissions is another thing if it effects you. My 73 runs great with round tops and the ignition . the carbs are from a 70 .. good luck

[beandip]

I forgot to mention that you dont need to change the intake that you have now .

[jcdozier]

Good advice posted above, especially the reference to ZTherapy. For a good bit less than a set of their state-of-the art SU's, you can get a rebuild kit for the ones you already have. I rebuilt mine last year, and compared to rebuilding something like a Holley 4-barrel, it was a stroll in the park. SU's are simplicity at work, and they work well.

IMHO, every SU owner should get a copy of ZTherapy's video "Just SU Carbs" that Scot Bruning made while he owned ZTherapy. With that and a flow meter (MSA sells them) you can tune your own SU's just as well as the "experts" at the Z shops.

[beandip]

That is vary true about the SUs being simple , and that they work well . A flow meter , uni-sen , is a must to get them ballanced with out one you are just shooting in the dark. If you want detailed info go to ztherpy.com good luck and keep on zzzzzzeeeen you can find the flowmeter at the local speed shop or check a motorcycle shop .

[justaZcarguy]

I bought the "Just SU's" video recently from Z-Therapy and I highly advise anyone who wants to tinker with their SUs to purchase that video. The "240 tune up also has excellent information in it and if you want to know how to take apart the carbs, clean and adjust them, then this is the video for you...

I have both styles of carbs for my '73 and plan to change over to the smaller dome style, I'm just waiting on finding the linkage and parts needed to switch over.

Enjoy, and order that video, I almost recommend the two-tape version of the video, it's a bit clearer.

[beandip]

Dumi, how about Z-nube insted. I found a good set of early SUs over the weekend . The whole setup , intake, linkage and aircleaner. If you are interested let me know, and I'll get you the E-mail address. If I dident already have a spair set I would have bought them my self. Any one doing a concours project these are the carbs with the drain in the float bowls. Just passing on info. nothing in it for me. I just want to keep these classics on the road. Good luck.