N49 & N54 Needles?

[240260280z]

Can't find detailed data on the net. (Comes up as "Repair Kit (B)" with "improved needles").

They came in an eBay "NOS 240z carb kit for 70-72 240z"

They are ~5mm shorter than stock 240z needles

Kit Supplier NJC Autoparts

Labels on box:

"Datsun x6010-E4926"

"39-5063"

Edited July 21, 2012 by Blue

[Bruce Palmer]

The chart I have only shows the n54 which was the smogger 240 needle.

As compared to the SM the n54 will run fatter at idle and leaner up top. The SM profile is just the opposite, they will lean things out at idle and richen things up in the higher RPM range that why they were the first step up the performance ladder in the How to modify Datsun Engines and Chassis book in 73.. Just depends on what you goal is....

Not having any profile info on the n46 it might be safe to assume they might run on the lean side at speed as well. Dunno.I'll check with Steve and see if he has anything....

Steve said he'll look in some non U.S. books and see what he can find on the N49 needles. He's not heard of them before. N27's were four screw needles N54 were in between and N58 were really crappy late smogger needles.....

P.S, Just got to wondering why that kit had new dampers in it. Anybody here ever wear out a damper? Ever in a million years? Every so often we'll get some cores in where it looks like Magilla Gorilla took one off whe Vice Grips but other than that can't guess why they would have supplied new ones.....

Edited July 21, 2012 by Bruce Palmer
follow up info

[Bruce Palmer]

I guess we collectively here at world headquarters of ZedTherapy don't know jack about n49 needles.

[Captain Obvious]

Blue, Are you sure they are N49 and not M49.

If they are M49, let me know, and I'll profile them for you. I have some of them, as well as the N54. I profiled the N54's but never got to the M49's... I got sidetracked by EFI stuff.

As for the length, don't worry about it. Even with the suction piston all the way up, that last station on the stock needles never sees the light of day. In other words, you should be able to lop that last station off the tip and never know the difference. At least unless you try to run ten turns down on your nozzles or something like that. :laugh:

Just got to wondering why that kit had new dampers in it. Anybody here ever wear out a damper? Ever in a million years? Every so often we'll get some cores in where it looks like Magilla Gorilla took one off whe Vice Grips but other than that can't guess why they would have supplied new ones.....

One thing about the dampers in that kit... They look like they have the metal top caps. If you keep backfiring your damper rods up through your plastic caps, the metal ones might last longer.

[240260280z]

Sorry all,CO is spot on. My middle-aged eyes misread N49 for the correct M49.

[Captain Obvious]

Haha! The only way I could even tell they had letters on them at all was with an eye loupe!

I'll get to measuring the profile on the M49s as soon as I get a few spare minutes. I don't have any SM's to compare them against, but I've done the N27's and can tell you how they stack up against eachother.

BTW - Those N54's were strange birds... It seems they have a flat spot at midrange where there is essentially no taper at all. Almost non-monotonic.

[240260280z]

Thanks! That is appreciated and all on the net who search will find your data too!

[Captain Obvious]

The chart I have only shows the n54

Bruce, Do you have a pic of that chart with the N54, or can you please list the station measurements? It would be good to know how close to expected numbers I'm getting with my measurements. :bulb:

Maybe Santa will bring me an optical comparator for the shop...

[240260280z]

......the n54 will run fatter at idle and leaner up top. .....

I'll concur...~14 a/f at zero turns of jet depth.

I think it may be due to the shorter needle.

[Captain Obvious]

I got a chance to measure some M49 and N54 needles today.

First, let me describe what I have... A while ago, I bought a NOS aftermarket rebuild kit which includes four needles, two M49's and two N54's. It's not exactly the same box as what Blue posted above, but probably made by the same manufacturer. From that kit, I measured a pair of M49 needles and a pair of N54 needles.

The measurements I got indicate that if you install the M49 or N54 needles into your typical round tops using 0.100 nozzles, you will run very rich. Richer than the SM needles. So rich, in fact, that there's got to be something unexplained going on. Either I've got needles that are mistakes or there's another explanation somehow. Since Blue put these needles into his round tops and got corroboration performance, I'm suspecting that my four needles are manufactured "as intended", meaning that there must be another explanation. After all, these needles were supposed to be lower emissions that previous versions?

What about a nozzle change? Did they use the same size nozzles in all years 70,71, and 72 or did they reduce the nozzle size somewhere along the way?

[240260280z]

I love the scientific method! Experimental observations backed up by data.

btw my eyes still hurt from running so rich

[Captain Obvious]

Yes, I believe we have great corroboration on the theory, but what about the explanation? Clearly those needles can't be used in the typical round tops on the typical Z car, but what gives? Those needles were used for some time with some margin of success. Bruce P refers to them as the smogger needles, so the inplication is that they weren't the best performers out there, but clearly we're missing something.

Improperly made needles? Used in conjunction with a nozzle diameter change? Something else?

Any idea?