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Identify My carbs, i think HS6 SUs not Hitachi. Good, Bad, Indifferent?


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#1 WogsRus

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Posted 28 December 2014 - 11:42 AM

Ok so my new Z came with what looks like to be HS6 not the early hitachies.

Can someone tell me what the main differences are and are these worth keeping or going to Z therapy 240z carbies with SM needles etc.

Current;y, ca pulls hard, however i have lowered the jet down another one turn as it was lean, now seams ok still a bit flat above 5600rpm and will not rev to anything over 7K not even at idle,that could be more the dizzy.

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#2 WogsRus

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Posted 28 December 2014 - 11:44 AM

more pics

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#3 dat2kman

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Posted 28 December 2014 - 01:28 PM

Leave them on it!
Seem to be working fine, a bit of a adjust here and there has helped!

As per your other thread, better to be looking at your dizzy for your issues.

#4 gav240z

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Posted 28 December 2014 - 03:46 PM

They look like HS6 SUs to me. Can tell by the nozzles. Why are you trying to rev past 7k anyway?

#5 gilltech

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Posted 28 December 2014 - 04:57 PM

SUs are fine, plenty of parts available for fine tuning them, why spend money to change for Hitachis which are so very similar?
And I really don't think you'd be wanting, or needing, to rev past 7.....why? Asking for trouble. Better to sort the car's gearing out to suit your needs.

#6 WogsRus

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Posted 28 December 2014 - 05:39 PM

Sorry should clarify, im not trying to drive to rev to 7k, its more the engine simply will not rev to that high, I was trying to say that in neutral just sitting there, jt won't get to that rpm it seams to break down at say 6.5k like it missfires.

#7 1600dave

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Posted 28 December 2014 - 05:55 PM

They're genuine british SU's (HS6).

Very similar performance between these and Hitachi's, nowadays how well they run depends on the condition of the carbs rather than what type they are.

Real SU's are easier / cheaper to get parts for, both standard bits and "tuning" bits. I rebuilt a pair a year or two back for a cost of under $200, including having the carb bodies re-bushed, new jets / needles / gaskets / special non-sink adjustable floats and high-flow ball valves for the float chamber. All the bits (except the fancy floats and needle / seat) were available from Carburettor Service Co in Sydney, who also did the rebushing. Fancy bits came from Burlen in Pomgolia.

Only thing I don't like is the method of adjusting float level on the British SU's - most of the 1 3/4" ones I have need to be adjusted by adding / removing shims / washers from underneath the valve (which is a little fiddly to get spot on). Hitachi's can be adjusted by bending the float lever. You can get (as I did) special adjustable floats for the SU's.

#8 1600dave

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Posted 28 December 2014 - 06:11 PM

Also, had a look in one of my SU books, according to the little tag on the float chamber in one of your pics that says "AUD661R" that carb is the rear carb off a '74 onwards Triumph Dolomite sprint with a 2l engine.

Perhaps you may need to look at re-jetting them if they are still jetted for the smaller Dolomite engine.

#9 WogsRus

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Posted 28 December 2014 - 06:16 PM

thanks 1600 dave much appreciated


#10 1600dave

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Posted 28 December 2014 - 06:29 PM

Out of curiosity, what size engine in your zed ?

"SM" needles are listed as British SU needles, I assume Z-therapy use these in their Hitachi carbs. You should be able to get a pair of these needles and bolt them into your carbs quite easily and cheaply.

#11 chris240

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Posted 28 December 2014 - 06:58 PM

Just a quick question, whats the difference between HS6 and what I have which are HU6 ? Does the middle letter, mean year of manufacturer ? The Hu6 I purchased new around 7-8 yrs ago..

#12 WogsRus

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Posted 28 December 2014 - 07:22 PM

they are in my 260Z running an L28 motor with an early E88 head i think. If they are still jetted to be from a dolomite, i might have an issue. Looks like i should check the jet size and the needle but i don't want to fiddle with it as it runs nice.

#13 1600dave

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Posted 28 December 2014 - 07:38 PM

Just a quick question, whats the difference between HS6 and what I have which are HU6 ? Does the middle letter, mean year of manufacturer ? The Hu6 I purchased new around 7-8 yrs ago..


Dunno, only types I know of are H, HD, HS and HIF. H & HD are quite old, HS is the most common type from the 60's / 70's, and the later HIF which are completely different with the float chamber built into the carb rather than bolted on the side.

Could be something newer I guess, I've only fiddled with older carbs.

The "6", incidentally, is the size - 1 3/4"



#14 WogsRus

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Posted 28 December 2014 - 08:52 PM

Ok so i took the HS6 carb jest out, stamped BCM. I also took a set of jets out of the spare set of 4 screw dome tops.

The HS6 needle is much longer and fatter then the hitachi one. The hitachi one will not fit into the HS6 carb as this has a spring loaded needle seat. SO i think SM needels are in order.

Thoughts>

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#15 WogsRus

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Posted 28 December 2014 - 09:12 PM

found this great tool, fantastic.

So people say an SM needle is to rich, so looks like next best mid ground is a SH needle. This is great.



https://www.google.c...jONW2aCgihXo7Kg


#16 WogsRus

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Posted 28 December 2014 - 09:26 PM

another problem, SM needles are not available in swing cab sets, so looks like i need to find something similar to an SM needle in a swing type

#17 WogsRus

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Posted 28 December 2014 - 09:54 PM

Ok so if SM is to rich, SH appears to be just right going by numbers. The closest to this is a BFN needle, so looks like i am getting a set to try, might be worth while.

#18 1600dave

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Posted 29 December 2014 - 07:37 AM

BCM is the standard Triumph Dolomite needle.

Also be aware that if the "SM" is recommended for an L24 (I'm not sure exactly what it is recomnmended for), it may still not be ideal for an L28 due to the larger capacity of the L28. Probably a good starting point though I guess.

I've already mentioned CSC in Burwood, Sydney, but SUMidel in Sydney also stock a large range of needles for $12 - $15 each - http://www.sumidel.c...gory/su-needles Don't be put off if they answer the phone as "Fabre" - once you start talking SU carbs, they put you onto someone else who seems to specialise in them, not sure what the business relationship is between SUMidel and Fabre ??

And just for completenes, if you get really carried away with a rebuild, here are the newer style floats that are adjustable, unsinkable and ethanol resistant - http://sucarb.co.uk/...ayup-float.html. Not needed, but make float level setting a little easier.

#19 WogsRus

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Posted 29 December 2014 - 01:02 PM

pulled my other set of carbs out, turns out they have a BAX needle in them, which is ritcher then the SM profile. HUMM, time for a test drive and see what it does.

fun and games

#20 WogsRus

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Posted 29 December 2014 - 03:02 PM

BAX needels = wholy shittttt what a difference. Need to lean out idle a bit but so far blood great. car now revs freely all the way to 8k if needed.




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