Fastededdie
Club Member
Hi all I am looking to fit SUs back on my car . I’d like take off the nearly new Tripple Weber 40s and out the SUs on . I’ve seen some from a 240 and I think they are the same as 260s 
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Fitting SUs Back
- Thread starter Fastededdie
- Start date
Fastededdie
Club Member
Getting fed up with the tuning up all the time . I know !
So the challenge you have is to find a decent set of SUs without worn out throttle shafts. Z therapy is the way to go but they have become super expensive.
I know a couple of guys here bought some rebuilt in the UK but that wasn’t cheap either.
Are those pics from eBay? Be very careful / clear about what you’re getting. I bought a set of 240z 3 screw SUs (for £350) to experiment with and I was told they were perfect - when I received them, you could see daylight through the throttle shaft bushes!
I know a couple of guys here bought some rebuilt in the UK but that wasn’t cheap either.
Are those pics from eBay? Be very careful / clear about what you’re getting. I bought a set of 240z 3 screw SUs (for £350) to experiment with and I was told they were perfect - when I received them, you could see daylight through the throttle shaft bushes!
Fastededdie
Club Member
I guess so . Iv now decided to keep the Webers and study them more . But they are a headache to be fair .
yellowz
Club Member
I seem to remember @Fairlineguy getting carbs serviced really well somewhere in Brum?
Albrecht
Well-Known Forum User
There's no good reason why correctly-fitted, correctly-jetted and correctly-adjusted triple 40-DCOEs would not be as good as gold on your car.
I ran a set of 40 DCOE-18s (as recommended by Weber) on a slightly warmed over L24 in a daily driver 240Z in central London for a decade. Never any trouble and certainly no need to constantly fiddle with them.
Carburettors are essentially just precision measuring devices. If they are fairly new rather than worn out, there must either be a problem with their initial settings, jetting or installation.
What are the symptoms?
Pretty sure it was these guys - http://birminghamcarburettors.com/ - happy to be corrected.
I know they are a total pain to tune if you don't have all the variations of chokes, emulsion tubes etc on the shelf + a rolling road and a gas analyser. BUT, I've heard those who have thrown good money at someone knowledgeable with all the right parts to set them up, are really happy with them and apparently they don't go out of tune for a long time after.
Also from what I've read / understand, most people over size their chokes in the belief that bigger is better, but those who want good road manners and less out and out top end performance have used appropriate chokes to get a decent mix of mid and top end power.
There are 5 fuelling conditions a carb (or any fuelling system) needs to take care of and the only complication (beyond having 3 carbs to synch) is that the DCOEs have a circuit for each.
1. Start-up
2. Idle
3. Cruise
4. Transition
5. WOT
With carbs, intake air velocity passing the jet (forgetting float levels for now) is everything. At low RPMs or when you crack the throttle open is where DCOEs can fall short if not properly set up with small enough chokes and accelerator pump adjustments / progression holes.
This is a GREAT read if you haven't already come across it. https://240260280.com/Tech/Carbs/Weber/DCOE Theory Operation and Tuning.html
Edit: Looks like Alan beat me to it at nearly the same time again!
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Fairlineguy
Club Member
Yep I’ve been using Birmingham carbs for a few years now.
They do a super job of refurbishing Hitachi carbs .(I believe currently getting ne throttle shaft made for them )
I buy a pair of rebuild kits from Rockauto and send them with the carbs it’s then about £200 from them returned
Attachments
I have a pair of Weber books for sale if anyone is interested.
Do they also plate / polish it all up? If so, they are the UK's Z Therapy alternative !
I have a pair of rebuild kits and a crusty set of carbs. please could someone take a photo of what I need to check to make sure they aren't scrap before sending them in?
Fairlineguy
Club Member
Yes they vapour blast then re zinc all bolts and linkage in either silver or yellow and polish the pot
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Robotsan
Club Member
I had the same question a few months back.. See this post and the following .. https://zclub.net/community/index.php?threads/twin-su-carbs-wanted.30585/post-353458
Ian Patmore
Well-Known Forum User
Chrasher, I used to run triple 40 DCOE's on a standard engine, there is no reason why they won't work as Alan says.
Rob Gaskin has just sold a good book, how to restore/tune Webers/ Dellorotos, a great book, I rebuilt my 48's using that. Digest the book so you know what everything does, even if someone else does the tuning, at least you know what they are doing.
AliK is spot on with chokes, air flow through them is critical for a good driver and potential power (even though the choke design is being impoved on as Weber have a stumbling point somewhere within the rev range, which is wrongly jetted out causing other issues).
Rob Gaskin has just sold a good book, how to restore/tune Webers/ Dellorotos, a great book, I rebuilt my 48's using that. Digest the book so you know what everything does, even if someone else does the tuning, at least you know what they are doing.
AliK is spot on with chokes, air flow through them is critical for a good driver and potential power (even though the choke design is being impoved on as Weber have a stumbling point somewhere within the rev range, which is wrongly jetted out causing other issues).
SeanDezart
Well-Known Forum User
I concur with Alan and Ian......properly serviced (ie in good condition) and properly set-up triple carbs should stay in tune. Personally I had a set of triple 45s on my L31 that remained perfect (proof was in the spark-plus colours) after the initial dyno run for 5x years until replaced by ITBs.
Interesting Neil ;-) thx for sharing.
Interesting Neil ;-) thx for sharing.
MCBladeRun
Club Member
Yes, @Paul Atkinson has commissioned them to make the throttle shaft, I've let Tony of Birmingham carbs know of my interest as well.
I used the contact form on his website to let him know and he did respond quickly too.
If a few more of us were to let him know of the interest in them, he could be a source potentially
I have also separately pinged him about the shafts too. I really want to kill modify my spare SUs with the Vizard mods! It would be great to have a UK source of the important parts for our carbs.
It would be good to have the bushing also as most will be worn.
As I understand it - and please someone correct me - the Japanese chrome plated the shafts to make them last longer / wear resistent? And I believe Z therapy make them out of Stainless Steel.
It would be good to have the bushing also as most will be worn.
As I understand it - and please someone correct me - the Japanese chrome plated the shafts to make them last longer / wear resistent? And I believe Z therapy make them out of Stainless Steel.
Re Triple twin-choke carbs needing fettling:
Once 'set up' and synchronised then they shouldn't need altering however it's that 'setting up' that is the all important factor. you have to know who can do it properly, that they understand your intended use and that they have the facilities and parts to get it right. Starting from fresh there are a lot of variables in Webers (choke-tube, jets, acc pump, float adjustment and 6 of most things!)
I had my trackday SUs (2") rebuilt and then 'set up' by an expert and they worked really well and I left them alone. I recommended the garage to someone but my guy (Trevor Shaw) had died and they didn't get the same experience.
The Webers on my Samuri received a lot of attention before I became the owner. My understanding is that the engine was built with 45s on it but when Jonathan bought it from the Z Farm it had 40s on it (that's not necessarily a bad thing, bear in mind that the size of the choke tube is the important factor for airflow and air speed and this can be altered to suit). He took me in the car in it's early days with him and it was awful imo. He took it to someone who spent a lot of time on it and it was better but still not right. A while later he took it to Kevin Savage in Cumbria (rally man) and he got it running ok and the car performed well but it was thirsty. It drove nicely even at low speed and was very free flowing at high revs.
IMO it was rich, backed-up by the fact that it would start easily from cold (couple of pumps on the pedal) and then tickover!
So my point is that two so called experts couldn't get it to run both economically and give good power. Driving steadily with normal traffic I could only get low 20s.
They can suffer from choke malfunction too even if the choke isn't connected. I think those 'in the know' prevent the choke from working?
So the moral is 'If you are spending a lot on your carbs (Webers, SU, Dellorto) find the right person to tune them on a rolling road' Money well spent. You can't just bolt carbs on to an engine and expect it to run well unless everything is standard as it left the factory.
Once 'set up' and synchronised then they shouldn't need altering however it's that 'setting up' that is the all important factor. you have to know who can do it properly, that they understand your intended use and that they have the facilities and parts to get it right. Starting from fresh there are a lot of variables in Webers (choke-tube, jets, acc pump, float adjustment and 6 of most things!)
I had my trackday SUs (2") rebuilt and then 'set up' by an expert and they worked really well and I left them alone. I recommended the garage to someone but my guy (Trevor Shaw) had died and they didn't get the same experience.
The Webers on my Samuri received a lot of attention before I became the owner. My understanding is that the engine was built with 45s on it but when Jonathan bought it from the Z Farm it had 40s on it (that's not necessarily a bad thing, bear in mind that the size of the choke tube is the important factor for airflow and air speed and this can be altered to suit). He took me in the car in it's early days with him and it was awful imo. He took it to someone who spent a lot of time on it and it was better but still not right. A while later he took it to Kevin Savage in Cumbria (rally man) and he got it running ok and the car performed well but it was thirsty. It drove nicely even at low speed and was very free flowing at high revs.
IMO it was rich, backed-up by the fact that it would start easily from cold (couple of pumps on the pedal) and then tickover!
So my point is that two so called experts couldn't get it to run both economically and give good power. Driving steadily with normal traffic I could only get low 20s.
They can suffer from choke malfunction too even if the choke isn't connected. I think those 'in the know' prevent the choke from working?
So the moral is 'If you are spending a lot on your carbs (Webers, SU, Dellorto) find the right person to tune them on a rolling road' Money well spent. You can't just bolt carbs on to an engine and expect it to run well unless everything is standard as it left the factory.
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