Carb set-ups

[dj240z]

Alright, i've had it with the SU's. I recentally purchased a 73' 240z and the other day i got royaly spanked by a toyota corolla. I cried, and then immidately started blaming the su carbs which i have never got to perform worth a darn. Its time to upgrade. I am looking for any and all suggestions on what the best carb setup would be for someone with completely stock engine. This car is going to be my day to day driver so i dont realy need something really hight performance, more looking for something that is very dependable but will give me a little better performance. What should i get, and where should i get it? I only spent $950 on the car and it runs like crap but other then one cylinder which is a little low on compression, i am putting entire blame on the carbs. I dont want to spend more on the carbs then i did on the car, but if thats what it will take, it might be worth it. What do you think? thanks, DJ

[jeffs73z]

Your z may have the original low emission flat top carbs which you immediately want to replace with rebuilt round top 70-72 carbs.

That will make a huge difference. If you already have them, you may need a good tune up and aother adjustments, such as valves, etc.

[Victor Laury]

I only spent $950 on the car and it runs like crap but other then one cylinder which is a little low on compression, i am putting entire blame on the carbs.

Sounds to me like you've got some work to do before you scrap the SU's

[seerex]

get you some 3 or 4 screw round tops and rebuild them kits are like 25 bucks and try them before going and spending money on new carbs , my brother has twin webers with cannon downdrafts and he is going to the 4 screw su's now , hard to beat a well set pair of su's , I would check on ebay or zbarn or maybe midwest z , good luck

[dj240z]

I already have the round top 3 screw su's. I admit that yes i have some timing issues and maybe im instore for a vavle adjustment and i am curentally looking for a electronic distributor, but i dont care about the rest of that crap.. I want to know about carb options that are not SU's. Thanks, DJ

PS: i have already adjusted the valves twice, and have played around with other possible options that could be causing my problems, and have prety much ruled out most everything but carbs. But i am just looking at my options right now, i am still going to od some tinkering after i get the electronic distributor before i just go out and spend an arm and a leg on carbs.

PSS:If i floor it from idle, like whne taking off form a light....it dies.

If i go past about half throttle, it doenst acelorate any more, it just blubbers.

PSSS: And to top it all off, the last time i went to open the hood, instead of it opening, i pulled about 4 feet of cable out onto the floor. Still not sure how im going to get the hood open now? hmmm.

[speedyblue]

Sounds like it may be starving for fuel. It might be worthwhile to replace the fuel filter and check the flow from the pump. If the rubber hoses are breaking down from the inside or something, that would cause a problem too.

It would seem there are a lot of people out there running tuff engines with twin SU's, so there should be no reason why you cant join them.

[Dan Baldwin]

You are aware that 240Z's with modified SUs have run in the 12s, NA, on pump gas, aren't you? If you're not willing or able to tweak what you've got into shape, bolting on a new set of carbs won't be a very good solution.

My carb recommendation for someone with a completely stock engine? '70-'72 SUs. What condition are yours in? Checked for leaks? Steady fuel supply? Piston drop test? There is Corolla-beating performance in the stock setup!

How low on compression is the one cylinder? You might consider trying to do a rebuild yourself, or dropping in a sound used 2.8 liter, which could be cheaper than 3x2 carbs, and would offer more real-world performance gain to boot.

[Daniel]

Pardon my frankness but it sounds like you want a quick fix for a $950.00 car. The odds are against that. If you go out and buy new carbs and new elec. dist. you are just throwing parts at it in search of a fix. I would suggest get the old car running in best old car performance before you take a chance of adding problems when putting new parts in. Get a good starting reference point.

[Chino 240Z]

So, when was the last time you open the hood since you pulled the rip cord?

I agree with giving it an all round tune up and consider the ZTherapy videos with some rebuild kits to get what you have running right. Then take it up a notch and spend the money on some modified SUs, upgraded ignition, headers, rear gears . . . but to just bolt on some new carbs and go? ain't gona run like we would like it to run.

I bet you'ld be amazed of how well your car would run with what you got just cleaned up and dialed in before going performance stuff.

[jeffs73z]

As mentioned above, fuel filters and pump are a good place to look. Also, make sure the little SU hoses beneath the carbs aren't cracked and leaking. I had that problem. You must use Nissan SU hoses from dealer (about $15). For $950, I bet your carbs still need a rebuild among other engine things.

Don't be angry at these messengers, most have been there, done that. If you got a relatively rust free chassis and a Z that runs at all for $950, you got a great deal!

[dj240z]

When i first got the car, it only ran on three cylinders. This was due to one carb which had been completely shut down. After doing some adjustments, I was able to get it running on all six. There is plenty of fuel getting to the carbs as i have removes the lines while running and seen it pumping. I beleive a lot of my current issues might be due to a non working vacume advance, but still not sure. I dont remeber how low on compression the one cylinder was, but i dont think it was horrible. I dont think the little lines below the carbs are leaking but if i ever get the hood open agian, i will defenetally check that.

I guess i should retract my initial stament where i dogged the su's. I am defeintally not going to buy some new carbs and expect everything to go well. I am going to get it going as best as i can before i go spend any money changing the carbs. But i have heard a lot of poeple say that the SU's do require a lot of tinkering with, not just intitally but all the time. I have four other projects to tinker with if i want too, right now i would just like one that i dont have to tinker with. Just something to drive and enjoy.

Is there a better system out there that would make it a little more dependable, so it doenst require as much attentions as SU's might? Or do you think that the SU's can be made to be as dependable and reliable as anything else for a lower cost?

Like i say, this is my day to day driver. or at least i want it to be soon, so i am not really looking to make it a speed demon, just want to make it dependable and reliable.

Thanks for the suggestions and help!!! DJ

PS: Got sorta ripped off whne i bought it, people clamed it was a 5 speed and i didnt check until a month or two later and it is only a 4. If any one has a cheap 5 speed they want to get rid of, im all ears. Also ..how am i suppose to get the hood open!!!!!!

[Dan Baldwin]

Cars are fun, no?

Non-functional vac advance isn't a problem. It only acts to give more advance under very light throttle cruise. At full throttle there's no vacuum. Your advance should be ~34 degrees max, with mechanical advance fully in.

I adjusted my SUs (when I had them) exactly once per set. I'm not saying they were perfectly tuned, but the car did run well and I never tinkered with them. Not to say that yours don't need attention. You won't find a simpler carb to tune. Have you checked for air leaks? Spray some WD-40 where the throttle shafts enter the carbs and see if the engine revs up. If so, you should re-bush with oil impregnated bronze or some such.

Have you removed and cleaned out the carbs? Might be worth an afternoon's effort. Checked the operation of the needle valves? Checked the carb pistons' motion?

I was looking at a 510 once and the guy called it a 5-speed. He was counting reverse!

Hood opening apparently requires a LONG screwdriver or prybar to lever the latch open from underneath (I've never had to do it).

Best of luck to ya, sorry you're having difficulties. At the ZConvention track day I instructed a guy with a pristine all-stock 240Z, and I was VERY impressed with the performance, though I'm used to tons more power. The low-end torque of the stock 240Z was great, and it pulled fine up to ~5500 or so. Great car, great motor. Though you still won't beat a modern stock 240hp Accord with it, you'll have 1,000,000 times more fun. Then when you want to mod, the sky's the limit for performance.