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Advice for an Amateur refitting SU carbs


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#21 HELLFIRE!

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Posted 29 December 2008 - 11:33 PM

I vaguely recall a company by the name of Fuel Miser as having gasket kits for the Hitachi's, but after a quick google search I can't confirm this. Dose Fuel Miser sound familiar to anyone?

#22 stevo_gj

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Posted 29 December 2008 - 11:50 PM

Hmm interesting. Thanks for the input Chris.

I think I'll wait until I've got it fitted, and if necessary upgrade the air filters afterwards.

#23 Zedman240®

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Posted 30 December 2008 - 08:32 AM

I vaguely recall a company by the name of Fuel Miser as having gasket kits for the Hitachi's, but after a quick google search I can't confirm this. Dose Fuel Miser sound familiar to anyone?


Yes it does! When I bought my first 260 with the flat tops and upgraded to the 240 carbs I bought 2 of those Fuel Miser kits from a carby shop in Oakleigh (Perfection Carburetors) and rebuilt them. This was in the late 90's though and I'm not sure if they are still available.

#24 Zedback

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Posted 30 December 2008 - 08:48 AM

I remember reading somewhere (maybe hybridz) that trumpets, or at least well formed inlet rings are essential when putting aftermarket filters on.  The mouth of the SU's causes a lot of turbulence which reduces airflow, whereas the stock airfilter box has well shaped inlets.  I can't remember any more detail than that, it might have only related to the very high performance end but could be worth doing some searching on...

#25 stevo_gj

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Posted 30 December 2008 - 12:20 PM

Yeah that does make sense I'll look into it thanks Mike  :)

#26 Zedback

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Posted 30 December 2008 - 08:03 PM

Steve, I've got two pairs I eventually want to freshen up as well.  So if you find any info, sources for parts etc. post up and let us know. 

One pair were fitted to an L28, anyone know how I identify the needles in it?
Mike

#27 stevo_gj

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Posted 04 February 2009 - 02:32 PM

Hey guys,

I was wondering if anyone in Brisbane would be able to give me a hand one weekend installing my new SUs and tuning them. I just spoke to the guys at Carb and Gas and they said I would be looking at about 400-500 to get them installed and tuned (assuming everything went perfectly) and 150-200 if I just wanted to tune them. It is at this point that everyone telling me to do it myself starts to make sense.

It won't be until March that I'm back in Brisbane to do it, but I'm sure there would be a carton in it for any good samaritans  :)

-Steve

#28 silverz

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Posted 04 February 2009 - 08:46 PM

Steve,
I live too far away to help unfortunately, however I hope this info helps.
When I first got my 240z it was running way too rich. I talked to so called Carburetor experts who told me to chuck the 240z Hitachi carbs as they are no good and will always run rich etc, their suggested cure was to buy British su's @ $800.00 for the pair with additional costs for fitting.
I was a little taken back at this and started reading the Haynes workshop manual and all articles on the internet as I was going to sort this out myself. I played around with it but was too scared to get too serious. luckilly a friend of my wife's came up to Darwin to visit with her husband who had a fair bit of experience on British su's. He helped me set my carbs up so it ran much leaner and the car pulled stronger, even though he couldn't get it quite right as it had a bent needle in the front carb - even better he taught me how to tune them myself.
Since then I have replaced the needle in the front carb and re tuned the carbs by myself. I was very happy with the results and when I moved back to Townsville I got the same friend to check my work, he only made a very slight adjustment to the mixture on the front carb. He was impressed with my work and I have to say it really isn't that hard. I say read up on it and have a go yourself. Make sure you have all the linkages etc and they operate properly and check the float levels on both carbs and reset if necessary- the Haynes manual will show you how to do this. Also ensure both pistons move freely when you lift them with your finger and they drop properly with a definite click noise. If they don't you will need to ensure the needles are centred properly. When you fit them have a go at tuning them yourself. The only fancy tool we used was a "su tuning hose" ( a metre long length of plastic tubing, cut off a roll I think was left over from when we had a water bed) We used this hose to listen to each carb and adjust the balance with the throttle adjusting screws until the sucking sound was the same in each carb. Simple but it works.
Anyway I am no expert but some of the people in these links I have attached obviously are there is some very good advice in these articles. Seeing as you are not going to do the job until March you could pick some info out of these before you start.
I hope this helps, I don't know much about the science of carburettors but it all seems quite simple providing you are patient and set them up carefully. Let me know if you want me to explain how we adjusted the mixture etc.

Regards Peter

http://www.sonic.net/~kyle/su.html
http://www.ztherapy.com/
http://www.teglerize...bs/techtip6.htm
http://www.teglerize...bs/techtip6.htm
http://dimequarterly...ech/sutech.html

#29 RBZ 260

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Posted 04 February 2009 - 09:23 PM

have you guys tried nissan for those gaskets?


#30 DoctorZ

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Posted 15 February 2009 - 01:48 PM

I had a lot of trouble with my flat-top SU's. I honestly thought they were worn out so I removed them and cleaned them up a bit including replacing the gaskets in the power valves with home made ones.
However, I never got a decent result from them until I put the K&N oval filters back on (not shown in the photo) and ran the air/mix breather and vacuum hose in to each of them. The design of the flat tops means you have another air inlet at the front carb which is supposed to balance air / fule mixture between both carbs rather than adjusting the needles. It's all good in theory but it's just another point of breakdown when these things start to wear out.
It's a pitty there doesn't seem to be any useful information on the flat tops or mods you can do to improve them and overcome their shortcommings.
Flat tops actually have some marked improvements over the older dome tops but at the cost of complication.

Looking at this photo now, I had it all wrong. The next step will be to reduce intake turbulence with some sort of Ram tube rather than the K&N filters
Posted Image

#31 silverz

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Posted 15 February 2009 - 04:23 PM

Doctor Z,
It is good that you can sort out the carb issues yourself.  I think we all have to learn ourselves as there seems a shortage of competent people to do it for us.
I know nothing about the flat top carbs myself as mine are the old round tops.

Zedback,
The needles in the round tops have the numbers stamped into them on the shoulder at the top of the needle (where they locate into the slide) Mine are stamped N54 which I think is the standard needle for an L24.

I'm sorry I didn't answer this earlier.
Regards
Peter


#32 stevo_gj

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Posted 28 April 2009 - 11:04 AM

Car started this morning as per usual, then stalled and the would not start again due to a flooded engine. Had to wait 30 minutes for flooded engine to subside, hook up an additional battery (mine was dying) and finally it started.

I really need to sort out the carb problem however I know I wont be able to find the time with uni. It's idling really rough currently.

I'm tempted to just spend the $600 and get Carb and Gas to fit and tune those 240Z carbys I bought.

#33 260Coupe

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Posted 28 April 2009 - 02:55 PM

Steve

If you can find a stock 240z air filter housing - install it!
Our Dyno tests on both my old 240z Sc race car and standard 260z road car have proven that the stock 240z filter housings (with inbuilt ram tubes) improve performance of up to 10% over ram tubes and socks or those lousy uni filters........so if you keep on eye out on ebay and see a see a filter housing ...grab it!

If you Zed is flooding then check your float height and ensure they have not holed and sunk....from memory it was around 3.5 turns out on each mixture knob would get it running with SM needles
For Hitachi gasket kits try the various Zed car shops in the US (Arizona Z car etc).....if in fact they are NLA thru Nissan

#34 stevo_gj

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Posted 28 April 2009 - 10:50 PM

Hey Alan,

Cheers for the advice. I'm currently running the stock 260z air box - I didn't end up getting the alternative ones.

I've got a pair of 240z carbys ready to throw on so I just can't justify spending extra money on the old flat tops I'm currently using. To be honest I don't even know where the mixture knob is  :-[

Once my current round of assignments is over I'll get the manual out on a weekend and see what I can achieve.

#35 Zedman240®

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Posted 29 April 2009 - 09:50 AM

We should make our own video on the 240Z carbs and stick it on youtube so everyone has access to it. Just basic tuning; where to start and how to adjust...

#36 stevo_gj

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Posted 29 April 2009 - 12:40 PM

We should make our own video on the 240Z carbs and stick it on youtube so everyone has access to it. Just basic tuning; where to start and how to adjust...


Hell yeah, that would be fantastic.

#37 S30Mike

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Posted 29 April 2009 - 04:55 PM

We should make our own video on the 240Z carbs and stick it on youtube so everyone has access to it. Just basic tuning; where to start and how to adjust...


Thats a fantastic idea :)

#38 Zedman240®

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Posted 29 April 2009 - 07:28 PM

Well, next meeting on the 12th we shall see what we can come up with..put all the "brains" together! hahaha

#39 2+2er

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Posted 29 April 2009 - 09:44 PM

I just got hold of a repair kit for $50 from:

http://cgi.ebay.com/...emZ190300207064

The needles are N47 and M49, it suite the 71 240z round top carbs. I have never pulled an SU apart but started to on sunday and found they where very easy to dismantle, clean, change out parts and reassemble. I completed one on sunday and am part way through the second.

i found in one of the float chambers that someone had replaced the float locking pin with a nail ???
Your flooding problem will almost certainly be due to an incorrect float level.

The video idea is great. I will try and get some footage while I have the second one apart.

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#40 stevo_gj

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Posted 10 May 2009 - 11:29 PM

Well Jospef's (josef's) dad has agreed to help me swap the carbys over on saturday week (23rd).

I've had a look at the condition of the carby's and everything seems to be A-OK. No need to buy a repair kit or replace any of the parts except one of the fuel hoses and one of the screws for the vacuum cover.

I was just thinking, since we are going to be doing the swap on a Saturday at his place, I should try and get together as many bits as possible beforehand.

It's a pretty straightforward swap from what I understand, but I've got a lot of hoses that will need to be blanked off and will probably be looking at removing the carbon canister thingy.

My question is for people who have done this swap before:

Were there any parts/bits that you had to pick up that weren't obvious in order to swap over 260z carbs to 240z carbs?




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