240z Hitachi Round-tops refurbishment / Ztherapy parts

[Graeme - CZ]

So it's winter, and what better time to get the carbs refurbished. I've found a chap locally in Edinburgh (Alan Wedgwood) who specialises in refurbishing SU type carbs, so my 240z Hitachi round-tops are going off for some TLC.

I have a few questions for the forum please. So I believe my carbs are likely to the be the original ones (1973 240z USA), but are attached to a 280z engine, gearbox and drive train. I've no reason to suspect that they have ever been altered from standard. I've also recently installed a fast-road header and exhaust line from Zstory.

With these things in mind, i'm wondering whether or not the carbs just get the standard refurb and reconditioned parts from Ztherapy, or if I need to upgrade in some fashion given the L28 and new headers?

Lastly, does anyone know of any alternatives to Ztherapy in the EU?

Thanks, Graeme

 

[Rob Gaskin]

IMO standard carbs would work ok and long as they are adjusted/tuned properly.

 

[240L31]

I'm running SUs on my 3.1L with great success. They are quite capable and often underrated for a street setup. You just have to get the correct needles as the original ones were chosen for only 2.4L displacement.

 

[Rob Gaskin]

I'm running SUs on my 3.1L with great success. They are quite capable and often underrated for a street setup. You just have to get the correct needles as the original ones were chosen for only 2.4L displacement.

So can you expand on the needles please? What needles are you using and where do you buy them from?

 

[240L31]

Needles were from Burlen UK.

I think I posted in in @AliK Topic: https://zclub.net/community/index.p...give-dcoes-a-run-for-their-money.25839/page-2

Ali, I just created an account for the sake of replying to your topic!

I love your scientific approach. I did a lot of tinkering with my SUs, too. I am certain that they can perform really well if tuned properly. My engine is a L31 stroker, running fully rebuild SUs with great success. I started with SM needles but the engine was running lean. Following, I switched the needles for RH needles which work great so far:

AFR 12.5 to 13.5 at idle/low cruise,
AFR 14 at high cruise (120-150 Km/h 3000-4000rpm),
AFR 12.5-13 at really high cruise (180-220 Km/h)
AFR 12.2-12.8 at hard acceleration.

The only thing I would like to change are higher AFR numbers during low cruise.
I didn't start changing the piston springs yet. Another issue to be analyzed: How important is the actual fuel bowl level? I'm starting to think that it doesn't matter too much (played around with no real effect).

 

[Graeme - CZ]

Needles were from Burlen UK.

I think I posted in in @AliK Topic: https://zclub.net/community/index.p...give-dcoes-a-run-for-their-money.25839/page-2

Ah, so you got needles from Burlen UK - not Ztherapy? Interesting. I'll have a read of this other thread.

 

[240L31]

Yes Burlen supplies the original su needles which are interchangeable with our SU Hitachi carbs.

 

[Fairlineguy]

Freind recently used a guy in Birmingham to have his hitachi carbs rebuild.
Came back looking really nice .(from memory about £250 )

http://birminghamcarburettors.com/

 

[uk66fastback]

That sounds (and looks) like excellent value for money!

 

[Graeme - CZ]

That sounds (and looks) like excellent value for money!

Yeah, great value.

 

[Graeme - CZ]

Yes Burlen supplies the original su needles which are interchangeable with our SU Hitachi carbs.

I didn’t think they would supply parts that would fit Japanese carbs, more traditional British SU’s.

 

[MaximG]

Freind recently used a guy in Birmingham to have his hitachi carbs rebuild.
Came back looking really nice .(from memory about £250 )

http://birminghamcarburettors.com/

This might be nit picking but worth a thorough chat with them if you were to use them. Z Therapy make a big thing on there web site about the reconditioning they do as apposed to others that just make it look good. Birmingham Carbs just talk about cleaning and re-plateing nothing about bushings and worn parts.

 

[Rob Gaskin]

Graeme, how was the car running? I'm trying to establish the condition of the carbs and the main reason for the refurbishment.

 

[istoo]

as i understand is the bearings on the throttle shaft on the the hitachi SUs get knackered for want of a better word. The Z therapy work i beleive put in a newer bearing setup, what exactly i dont know.
I would get the chap in edinburgh to have a look.

Really interested to see how you get on with this Graeme...

I have SM needles in my hitachi SUs which run well.

 

[uk66fastback]

ZTherapy give the butterfly spindle shafts stainless steel roller bearings ... I think that’s where most of the expense is incurred.

 

[Bazzateer]

I'll have to check but pretty sure there's an invoice from Z therapy for recon carbs in the file for my Z.

 

[uk66fastback]

Here’s what I paid ...

 

[toopy]

I didn’t think they would supply parts that would fit Japanese carbs, more traditional British SU’s.

They don't technically, but Hitachi SU's are licensed copies of the British SU, with the Japanese putting their own design spin on them, but importantly and conveniently, the needles and i think the springs inside the dashpots are the same.

 

[Farmer42]

They don't technically, but Hitachi SU's are licensed copies of the British SU, with the Japanese putting their own design spin on them, but importantly and conveniently, the needles and i think the springs inside the dashpots are the same.

They are licensed copies of a British SU design meaning they look near enough the same and operate the same but that is where the similarities end. The Hitachis are metric whereas the SUs are imperial so all the SU fittings (except the needles and dashpot springs) will not fit on Hitachis. With the Hitachis, the problem is mainly on the float valves and the throttle shafts which wear and get vacuum leaks which prevent smoothe running. The SU float valves have a different thread (imperial) so wont screw into the Hitachi float lid (tried it!). You could probably get the throttle shaft bushes made but the shaft itself is a different tolerance and size as is the butterfly valve. As far as I am aware only Z-Therapy replace throttle shaft bushes on a Hitachi and I don't think the refurb kits provide these or the shafts/butterflies.

IMO if you buy the refurb kits without replacing the bushes etc, you could be wasting your money if the other parts are worn. This is why I decided to go full British HS6 SU because you can get all the bits at a fraction of the cost and a lot quicker as Burlen are UK based. If the Birmingham company use SU parts on Hitachi's I would be interested to know how they do it and what they provide.

 

[Graeme - CZ]

Graeme, how was the car running? I'm trying to establish the condition of the carbs and the main reason for the refurbishment.

Hi Rob - the car was running ok to my untrained eyes, maybe a little rich though. Given the new headers and exhaust it needs a tune up, hence i've decided to have my carbs fully refurbished with a specialist who will use Ztherapy parts. I just want it to run as well as it can, and also be optimised for my setup - 240z Hitachi round tops, E88 head (probably from a 260z) and L28 (N42 block).