I don't think it makes a difference, one way or the other. Spinning them would be more of asn exact science is all, something measurable and recordable.

 

I'm in touch with zTherapy and just fired an email to an SU outift in Australia regarding needle selection. I'm tempted to file a tad off the idle neck of these needles, but I'd rather retain them the way they are and play with others instead.

 

Rather than filing them right now, would moving the needle up into the piston, for example placing the non-tapered neck flush with the piston recess, cause a problem with how the carb operates?

 

Snowing/Raining today... Finishing up the stereo install I guess.

Edited April 23, 20159 yr by oranngetang

 If you move the needles up, it is the same as lowering the jet nozzle.  You may gain at idle but you will loose at WOT and cruise just like when you were 3 turns

down.

 

Your only solution is to remove some of the needle in the first two 1/8" stations below the shoulder.

 

If you use a flat file you can measure needle thickness from the flat cut to the back side to compare both needles.

 

You can also use your O2 sensor to measure your cuts.

I gave it a go without much success. Perhaps I removed a little too much material, maybe not. It seems at the point where the engine doesn't want to run do to lack of fuel, I can decrease the jet height by say, 1/8th turn and the revs will increase to the point the piston lifts slightly, which seems to give MORE fuel and it further increases, gets too rich, slows down, bogs, leans out, piston raises, etc... So it'll wander-idle now, depending on how I set it. 

 

I'm pretty much at the point where I don't even want to look at the car today as the diff mount has also shaken itself loose again... But, I may try removing the piston spring and placing a washer or two on the bottom, to see if it'll hold that piston down, until there is a little more vacuum. I'll post any findings...

 

Looks like SUmidel has ~120 different needles for their british SUs. Given they come in .900, .100 and .125 variants, would the length be close or the same to work with our Japanese SUs? HS6 needles must be similar if not the same?

 

 

 

how do these needle grinds compare to the stockers? or is one of the ones shown what came as oem?

 

Looks like SUmidel has ~120 different needles for their british SUs. Given they come in .900, .100 and .125 variants, would the length be close or the same to work with our Japanese SUs? HS6 needles must be similar if not the same?

 

 

Hitachi SU's on our Z's have 0.100" orifices in the jet nozzles.  Different size nozzles can be purchased.

I should amend. 272 variants of 0.090" needles, 226 variants of 0.100" needles and 73 variants of 0.125" needles...

If they all 'fit' then there appears to be a hell of an aftermarket variety out there.

If anyone has a PDF bible of what the tapers measure, here's where to post it

how do these needle grinds compare to the stockers? or is one of the ones shown what came as oem?

 

 

Substitutes for stock L24 SU:

http://www.classiczcars.com/topic/28785-su-needle-specs/?p=255075

 

Some CO profiling of stock in this as well as Madkaw SM measurements:

http://www.classiczcars.com/topic/42685-dynojetted-the-l24-today/

 

The Beware Needles (CO profiled and bailed me out) Great Bruce info too:

http://www.classiczcars.com/topic/43876-n49-n54-needles/

 

Interesting data on SM's:

http://www.classiczcars.com/topic/17754-another-sm-needle-question/

Here is a great 510 thread for 2 litre 4 cylinders needle mods:

 

http://community.ratsun.net/topic/57757-needle-modification-for-l20b-sus/page-3

 

 

IF you had 3 SU's these needles would be close

Edited April 24, 20159 yr by Blue

Been trying to adjust out the acceleration flat spot with new SM's. Seems OK (very nice at part throttle) but miss (burbling) at WOT transition from cruise. If I drop the jets enough to tune out the miss, then it's too rich everywhere else and would foul the plugs. Guess some polishing needed. It helped a lot with the N-27's, just needed a bit more. You have a lot more engine, so I doubt if "out of the box" SM's would help.

 

More or thicker oil in the dashpots might do something, as far as making it harder to push up the pistons.

I agree Stanley, try a thicker oil to tame the transition and make it richer during transition.

@ 3. I've got some reading to do when I get back to the house.

so the carbs are super simple, but he devil's in the details w/the needle and damper oil.

no such thing as a free lunch in the world of tuning...

 

i'm thinking about putting a pair of wideband sensors in the header to tune mine with the new engine build - hope to avoid hours of trial and error.