Try and get the A14/15 H89 head which has high compression (heart-shaped) combustion chambers and oval intake ports.

I think DVLDAT was thinking of a single application.

Here is a thread on this matter and it may be easier than thought with a little creativity.

Twin Downdraught

As said, it seems to benefit high rev applications.

What program is this? Very intrigued.

I did the same initially but the 120 primary eas too small to work for my engine. I now have a different 32/36 on and the 120 primary works fine. Just trial and error if you do not want to dyno and I know this is a real pain having to swap/buy jets. In my opinion, if it is an A12, this all occurs because the 32/36 is too big for the motor as smaller venturis are needed. This is why I toyed with the idea of a 28/36 Weber where venturis could be removed and swapped. The restricting intake manifold of the A12 and the adaptor kits sold which defy thermodynamics and flow do not help. A 32/36 flowing into this is heavily choked.

As they say; just my two cents.

Killer1200, does your book have the specs for a M89 or M92 needle? I do not have these in my information.

Thanks for everyone's help

I found the no.4 and no.5 needles you mentioned but they may be a little rich for my A12 application. I did however find this info on this Japanese web page Hitachi SU GX specs

Freak, what does he mean by no.4 and no.5?

Yes, those are the sizes I am looking for as they show the size of the needle in inches thus showing the tapered nature. I can then match these to the genuine SU needles and find a match.

I just need to know which one was used on the GX. I found a site that said the M66(SSS) and M83(GX). The site was to do with L16 engines but I thought the GX needle (M83) might be the one.

Thanks for the help so far.

The problem is the guy at the Carburettor shop is a wanker who I have seen before and given information that could be seen to be incorrect and the guy at Swift Automotive, who I bought my SUs off, did not want to otherwise know me. They only sell used SUs and parts, do not tune and do not refurbish them to your requirements (ie. bushing the throttle spindles) but instead only offer a full refurbishment to British car specs at a princely sum of around $600. He would not help me in my quest except for when I find the needle specs I need.

I have thus schooled myself on SUs as much as possible and have made a full assault on the web for information. I have a program (Haystack) which helps but as I have lately ditched my plans for a Lambda sensor and subsequent air/fuel ratio gauge, I believe the easiest way is to find the Hitachi needle size such as M83 etc and match to SU counterparts.

It is a shame that as I continue through my experience with vehicle modifications I find these following traits that are always present in businesses (at least in Christchurch):
1/ Unwillingness to help
2/ Sky high prices for this unsatisfactory service
3/ A lack of knowledge
4/ The combination of all of the above resulting in the modern day preference of bolt-ons and the lack of creativity or ingenuity

Thank god this site exists as the free info on here beats everything else

Does anyone know what needle for the GX Hitachi carbs is used? ie. M83, M66...
I am currently trying to get my SU setup on my 1200 engine and any help would be great. Thanks