su carb needles

[highway star]

i have a pair of 2" su's (HS8 type) fitted to my 260z with k&n filters. it went on a rolling road recently and i was informed that the needles were wrong as the mixture was very lean and was lacking top end power and that there are possibly dozens of different needles available. as i'm not very technically minded, could anyone recommend which type of needles i need?

 

[Mr.F]

Quoting from the old Z Club magazine article on this subject ( Autumn 1987!):
for fixed needle type 2" SU use OA7, part number AUD 1277 as a starting point.
Variations include KL / AUD 1536 - weaker mid range, richer top end
KU / AUD 1554 - same mid range, weaker top end
RJ / AUD 1292 - rich mid range, same top end.

All comparisons made with OA7.

Response can also be modified with varying spring rate. Try:
AUC 4826 11.25 oz; red & green markings
AUC 2107 4.5 oz; light blue & black markings
AUC 4818 18 oz; light blue & red markings

Make sure the carbs are set up for needles in the 0.100 jet series (some are 0.090 series). Convert using CUD 2752 jets.

Acknowledgements to Steven Jones whose fine research has provided an invaluable resource passed down over the years and even used by Burlen Fuel Systems as a reference guide!

 

[highway star]

thanks mike, thanks also to steve jones

 

[highway star]

hi mike forgot to mention the needles are spring loaded and not the fixed type so the the one's you suggested are not applicable. any further advice greatly appreciated

 

[Mr.F]

Very limited swinging needle selection! Steve Jones' article suggested BAR, S.U. part number CUD 1115.
I have since seen suggested also the BDL needle.

It is suggested that you should be able to fit the later needles into the swinging needle seats...?

 

[highway star]

thanks once again mike, that's great info!

 

[ianh1968]

thanks once again mike, that's great info!

Hello All.

I found this thread because I was looking for info on SU carbs....

So far as I know 100thou swing needle BCD is an exact copy of 100thou fixed needle OA7, but BCD is 2 index points longer as it is a "swinger".

I have made a spreadsheet which contains the needle tables and several features to compare needles. It compares by 'exposed area', so it can validly compare needles which are 125thou with needles which are 100thou.

It also enables you to enter "hybrid" needles and find matching existing ones. I used it to find the BCD needle match, it took me about 30seconds....

The spreadsheet is in OpenOffice format and if anyone is interested, they can let me know.

Ian

 

[Mr.F]

Ian - would you be prepared to allow your spreadsheet to be published in the Technical Section of this site?
Regardless, I would be interested in a copy to use for my own recommendations. If it could be emailed, my address is mike@mjpauto.com.

 

[ianh1968]

Hello Mike,

I read that your email has been "broken"....

I sent you the needles.xxx.ods spreadsheet to mike@ - Do I need to resend?

Back to your first reply to the original post, I thought that the 2" SU's had 125thou jets. From what you are saying, it sounds like there may have been a small jet conversion as well, but I am totally guessing that this would have been 125thou to 100thou, not 100thou to 90thou.

Again, I am guessing that most of the 90thou needles would be too short for the 2" carb and would probably get pulled right out of the jet giving a hugely rich mixture.... In my email to you I compare the 100thou OA7 with the 90thou No7 needle which is only 13 index-points long. This would be too short for a 2" carb, unless the dashpot piston travel is restricted.

Regards,

Ian

 

[Mr.F]

I have your spreadsheets safely, but have been "off line" for emails for a few days - fixed now.
I've not had much time to play with your data, but it is very comprehensive abd should be of use to future generations of Z owners.
The data I use is from a tried and tested Z Club article which is also kept on record and used by Burlen, so I have to assume all is OK with the applications...