Wot needle for 2" SU's on L28 engine

toopy

toopy

Club Member
I'm going to be pulling my carbs apart to clean and then fit new fuel inlet valves and check the floats etc.
The car runs ok and has passed an MOT as is but i cant stop it running a tad rich!
I was just wondering what needles other people were using with a similar setup to mine, see signature for spec :D
I will be taking it for a rolling road session at some point, i'd just like to know
what needles others have had good results with.

Thanks, Anthony
 
If you are taking it to a rolling road then I would leave the needles that are in there alone. If the rolling road guy is any good then he will be able to reprofile the needles that are in there to meet the requirements of your engine/cam combination.The good thing about SU carbs is the ability to reprofile the needles and therefore get a much better fuel air mixture without so much of the compromise that you get with fixed jet carbs, webers dellortos etc.
Just my opinion but it is what I have done in the past. I can almost say that you will not get a needle that will go straight in and be the right one all through the rev range. Cheers ben
 
Needles

You could give Burlen Fuel Systems a call as I'm sure I've seen their name mentioned in other threads where people have asked the same question as yourself, might get you in the ballpark and then have them fine tuned on a rolling road as Ben says

Tim
 
I believe Burlen still have on file the Z Club magazine article from Autumn 1987 which gave the following advice on needles and springs as a starting point for moderately tuned 260Z:

Needles

Swinging type (HIF?) BAR (part # CUD 1115)
I have seen suggested elsewhere that BDL may be a suitable alternative (no part # available, but Burlen will know what BDL means!)

Fixed type (H and HS) OA7 (part # AUD 1277)

Options for fixed:
KL weaker mid range, richer top compared to OA7 (#AUD 1536)
KU mid range same, top range weak compared to OA7 (#AUD 1554)
RJ mid range rich, top range same compared to OA7 (#AUD 1292)

Fixed needle carbs (up to 1971) may be fitted with 0.09 jets. Convert to 0.10 jets using part #CUD 2752 - two of)

Springs

Mid range spring 11.25oz, colour coded red/green (#AUC 4826)
Weak spring 4.5oz, colour coded light blue/black (#AUC 2107)
Strong spring 18oz, colour coded light blue/red (#AUC 4818)

Material originally researched by Z Club member Stephen Jones to whom all credit due! His article also contained advice on sourcing the carbs, making the linkage, modifying the manifold and water pipes etc.
 
Cheers mike, excellent info as always :bow:

Think i'll ring Burlen then.

Thanks all ;)

Anthony
 
Yes excellent information from Mike and good for reference as a stating point.

From my experience Ben's advice is also very useful and practical.

I don't know what needles, springs etc I have in my car. After my engine was rebuilt/modified and 'taken out' to 2.8 (about 4-5 years ago), I had the carbs cleaned and rebuilt, I ran it for a about 400miles and then got it on the rolling road. The guy who tuned it was Trevor Shaw (sadly no longer with us). He had 'done' a few Datsuns and was able to get it running well by 'reprofiling' the needles with emery paper and stretching the springs (to make them stiffer I assume). No new parts were fitted. The timing was set by a guy turning the distributer with the engine running at about 4k I think. He told me to experiment with different viscosity oils in the dashpots too (I've not done this).

I haven't touched any of these mixture/ignition settings since because I'm happy with it. I realise that there may be benefits from a more scientific tuning session and experimentation with needles, jets, piston springs, ignition advance springs/settings etc. That can come when there are no other jobs to do.
 
experiment with different viscosity oils in the dashpots
Click to expand...

The manuals will suggest lightweight oil, e.g. 20W; Steve Jones (and others) would suggest that 20W-50 engine oil gives a better result and more progressive piston movements. Need to couple this with spring experimentation (or stretching!)...
 
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