After I’m done replacing the diff and tranny in my 260z I would like to get rid of my crappy flat top carburetors. My original thought was to go with round top SUs from Ztherapy which is what everyone on the forums seems to be recommending. Unfortunately the price is rather expensive. I don’t have any of the cores so if I read their website correctly it will cost me 980 for the carbs, balance tube, and linkage.

The guy that sold me the transmission has been working with Z cars for a very long time and he recommended converting to a 4 barrel carb using the Arizona Z car manifold. The carb he recommended was the Edelbrock #1403 500cfm (not the Holey 390). This seems was a much cheaper option, 300 for the carb and 300 for the manifold.

I am very much torn between these two choices so I thought someone might help me out. I am not going to be using this car for racing anytime soon (much as I want to). It will be driven on a more or less daily basis, so the system has to be reliable and as fuel efficient as possible. Performance is also a factor, I’ll tend to weight my choice toward what brings more power to the car. Finally, price is also a factor as I am on a pretty tight budget (I’m a student).

If the performance and fuel efficiency is about the same I’ll go with the 4 barrel conversion. If there’s a definite advantage to the SUs I’ll go with those. Can you guys help me out?

Check out part #ZT161 for $730 which takes into account the fact that you have no cores. The $980 item ZT162 has items in addition to what you really need.

I'll let others chime in on what they see as the advantages of a set of carbs that allows the air fuel mixture to flow straight into the intake ports or a carb that makes the air fuel mixture take a hard ninety degree turn before it goes anywhere...... Sorry, I've wanted to say that for a long time, and thought today, while no one was looking, would be a good time. ROFLROFL

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The guy that sold me the transmission has been working with Z cars for a very long time and he recommended converting to a 4 barrel carb using the Arizona Z car manifold. The carb he recommended was the Edelbrock #1403 500cfm (not the Holey 390). This seems was a much cheaper option, 300 for the carb and 300 for the manifold. ...

There are many viewpoints in the archives here, but my 30 plus years of personal experience is that SUs are clearly the superior product.

Will

I just ordered my 4th set of Z Therapy SU's. They're worth every nickel! They come back working and looking better than new(not to mention the simplicity of the SU carb). Bruce have you mailed my 3 screw carbs yet? Guy

Ditto, The Z Therapy SU's are the best way to go. They look clean and correct when you pop the hood, perform better, better fuel milage and drivabilty. Plus they sound better when you wind it up.

I agree with all the above. Just like I said in the PM. Four barrels are great on a V-8 when it can sit in the center of the engine . On a in-line engine , not so much. Many things have been tried over the years . If you do decide to go with the SUs , use the present intake , you will need to change the linkage between the two SUs because the space is different. A early air cleaner also is the best way to go. You can do a search on this . Gary

I've used a range of Holley four barrels on my L28 for years. :stupid:

They're ok but to truly get them running right for the engine for which they were never designed to be on, takes quite a bit of tweaking.

I'm currently getting a #4548 Holley 450 cfm four barrel worked over by a professional carb rebuilder to suit my L28 after an extensive dyno session identified a number of areas that needed reworking on my #1848 465 four barrel. Basically, the fuel curve was all wrong. The boosters and emulsion tubes are being replaced/modified on the #4548 to suit my combination. You can't generally do this at home unless you've got an intimate knowledge of Holley's and the tools necessary to change the boosters.

So what you get when you buy a Holley four barrel is a carb where some but not all the fuel characteristics can be modified by the backyard guy and achieve roughly 80-90 percent success.

Then there is the HP series of Holley's. The #80507 is a four barrel 390 cfm double pumper but even this performance carb doesn't have an adjustable metering block(s) but the boosters are doglegs which are better than the standard jobbies.

So what is one to do? It would seem to me that for the Z guys out there, a properly worked over set of SU's are available over the counter. That's really hard to beat for convenience my friend.

Good luck.

What about the SU rebuild kit from ZTherapy? It only costs about $100. Used SUs can be gotten for anywhere from $50 to $200.

i have the 3 screw carbs that i bought 14 yrs ago. only recently did i buy a new rebuild kit. carbs make my car run better than ever!

Another vote for the ZTherapy carbs. I know a grand is a lot of money, but they are worth $400 more than putting on a carb that the motor just wasn't designed to work with. The ZTherapy carbs are worth every cent. Just my opinion.

These cars were meant to run with the dual SU's, or a triple carp set up like triple mikunis, look at Zs-Ondabrain's pics, and even send him a PM. Myself, I was going to go turbo, but, starting to lean more towards the triple carbs, more aggressive cam, having the head port and polished with a more aggressive exhaust.

If you have the flat tops, that means you probably have the N36 intake manifold, which has been rumored to breathe better than the E88s on earlier models. I would suggest keeping that manifold, getting a balance tube for the roundtops from a junkyard or other private source (*ahem* there are many on this board alone *ahem*), and get the 4 screw SU package from ZTherapy.