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Holley Carb or SU'S


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Okay i've searched and never really found any clear decision. which is better as a daily driver setup, the holley 390 cfm or the su's? i found a good holley carb and arizonaz setup off craiglist pretty cheap. right now my su's are running pig rich and thought switching over to the newer system would help me out. So i know rules state there is no best... so which one is better for my purpose?

 

Jon

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It is kind of a hard read when the promoter of the thread is the owner of the company selling the kits. Of course it is the best.

 

My opinion, if you want set it and forget it, at least for a little while, go w/the 4 -barrel. SU's from what I've read up on and currently drive are great for performance.

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yeah im still leaning that way. the only problem is that my car at one time was set up for efi and im debating on switching it back over. i need the manifold and rail and injector but my car already has the ecu and wiring harness for the injector in it. Would it be worth my time/ money to switch to efi? i can get the whole holley setup for 350-400 i think can i do the swap back for that much?

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Get a set of Ztherapy carbs and set it and forget it. Performance wise the S.U.s thats what the motor was built for side draft cant see the down drive carb giving you any better performance besides easier tuning if you are familiar with the holley carbs.

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I have a set of z-therapy carbs and absolutely live them! It's so much easier when your SU's work like they're supposed to. Super easy to tune, great response, awesome performance.

 

Plus, that tone of side drafts (although they're no webbers) is unbeatable! :)

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For the record, I'm no expert so my thoughts here could be completely wrong but I was in a similar situation last year with my car. I wanted to replace my flat top hitachi's and couldnt decide if I wanted 4-barrel or SU carbs. I searched a lot but never got a good answer on which setup works the best. There are people who swear SUs are better and others say 4-barrel is better... I just assumed theyre both ROUGHLY similar in performance and made price a deciding factor.

 

From Ztherapy a nice new set of SUs would have cost me between 700-1000 since my hitachi carbs were no good for their core charge. On the other hand I got a new arizona z manifold for like 300 and a used edelbrock carb for 150. A brand new setup would have cost 300 for the manifold and around 300 for the carb, so slightly cheaper. Anyway,I went with the 4-barrel and am very happy with it (over the hitachis, since I've never run SU carbs I dont know what they feel like). It seems to run really good, albeit still a little rich but that's just a jet/rod change away, and I'm working on finding the optimal setup. It makes a nice noise too, and I like it because its a little different.

 

For you, since you already have a set of SUs to give as cores, Ztherapy rebuilt carbs wont cost much more than the 4-barrel, depending on how cheap youre getting the it. I dont remember for sure but I think Ztherapy also offers rebuild kits for SU carbs too, so something else to look into.

 

Ultimately, I think it kind of depends on what you actually want to run since both setups have been made to run well. If youre in Portland (oregon) come to the Canby meet this weekend, the owner of Ztherapy is going to be there and there is bound to be one or two people with 4 barrel intakes as well.

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If you are having lot of problems with the SU's there are several books and even Z Therapy has a dvd with how to rebuild and how they work. I bought a book for like 5 dollars on ebay and the SU carbs (IMO) make a lot of sense, they just look very complicated.

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I love my SUs. The car runs like a million bucks. The throttle is responsive, and I couldn't imagine any 4-barrel running any better. Everyone I know who hasn't had experience with the SUs tells me I should get rid of them, but I would probly convert to FI before going with the 4-barrel settup.

 

There are a few videos on you-tube as well that helped me out a great deal getting the SUs tuned right. Now, if your's are worn out and don't work well, that's another story (you might never get them to run right without a rebuild). Depending on your altitude and setup you may have to look into new needles.

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Thanks guys for the advice. yeah im planning on going to the canby meet tomorrow and check out all of the different cars. right now since its is kinda half way done for me i think i'll just convert it back over to FI. Im thinking a whole new motor will be a better swap then all the little bits and pieces. But who know mayne i'll see an awsome 240 with su's and change my mind.

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I get a real kick out of reading the SU vs. Holly carb stuff here. Since I am older than most of you I remember having SUs on my 1960 MGA when I was in college about 45 years ago! They were regarded as OK but a pain in the rear even then. They are simple and efficient technology but they are ANCIENT technology. They were a pain to syncronize and tune 50 YEARS ago, doesn't that say something all by itself? The Holly is a more modern design and with four barrels is more efficient and simple for moving air and fuel. For everyday use I'd pick the Holly over multiple SUs any day. But for 21st century drivability go with EFI.

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Get a set of Ztherapy carbs and set it and forget it. Performance wise the S.U.s thats what the motor was built for side draft cant see the down drive carb giving you any better performance besides easier tuning if you are familiar with the holley carbs.

 

WERD!!

 

However...I have seen a local 280Z with the 4bbl Holley and the owner seems to be sold on it.

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  • 2 weeks later...

I have switched over to Holley (390 cfm) for my stock 240 engine, because I also had a '60 MGA that had SU's. Didn't like them then or now.

Holley seams to be the way to go, but, for the members that do have a Holley, which main jets do you start with?

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  • 2 weeks later...
Guest Rolling Parts

Both probably have their advantages and disadvantages (there is no best).

The truth is that you don't see the disadvantages when using a single 4bbl/Azcar setup for a daily driver. Basically the single 4bbl just works fine out-of-the-box and will work fine for year after year.

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I really have to say, I am in almost the same exact position as you are. I have done extensive research and seen all sides of the debate, and the conclusion I drew was this:

 

There are so many people who swear by each and every one of these setups, so it must mean that they all can do their job just as good as the next one, provided you know what you are doing.

 

THAT BEING SAID, there is one bit of info that might help. I was talking to the guys at Motorsport Auto, and several of them couldn't decide between the SU's or the 4 barrel, however, there was one constant theme:

 

the 4barrel is much simpler and easier to maintain, and the 4barrel will enhance the effects of all future upgrades to the engine.

 

The deciding factor was when I finally figured out that modern technology and simplicity is more important than saving a few bucks. Not to mention any speed shop can work on an Edlebrock or Holley, whereas you need a specialty shop for the SU's.

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All things being equal, there is a performance advantage to the "straight shot" design of sidedrafts! With a 4 barrel, there are several severe corners to flow around that will cut down on air flow into the motor, hence, performance. A good set of SU carbs (rebuilt or new) will give you 90-95% of the overall performance of EFI, can't say that is the case with a 4 barrel setup. Since you have the option of getting the parts and plugging in the EFI, I'd go that route. Being a Chevy & Datsun guy, save the 4 barrel stuff for a V8, but only the older stuff, as EFI and direct ignition on the new motors can't be beat. :) Just my 2 cents.

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