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It is interesting comparing the 35mm to the 36mm choke. By Shifting the curves on top of one another and ignoring the a/f offset, the shape is the same except: - The 36mm is much leaner in the low end. - In the middle just before the peak the 36mm gets slightly leaner then it gets slightly richer at the peak. (Below)By aligning each plot to the AF Scale, 36mm seems to be richer in the mid to high; but this may be due to the variations that seem to be going on with the meter. One would expect the opposite: more dilution due to less venturi pressure drop (aka signal) to pull the fuel out of the well with the larger 36mm choke.

The curve is a lot flatter in the lower RPM's than the F16. This is very interesting. btw the Weber Tuning Manual recommends F2 emulsion tubes for cylinders whose range covers the L28 displacement. You should also consider 240 airs.

Be wary of Hybrid Z posts...especially the Weber stuff on that site. The scientific method is usually missing. They did not even recommend changing E Tubes in the thread nor could I see a mention of it? If you look at the range of their curves in the thread you references, it is > 3 A/F Ratio points, your best is less than 1.5 with the F2 and 2.3 with the F16. For your solution, the F2 will need smaller mains. Fuel height is another tuning parameter but it is labour intensive so we can call it quits for the testing and I can pick it up again when I get my SK's installed. They have external fuel adjustment. to make things easier.

http://www.reuters.com/article/us-nissan-safety-checks/nissan-to-recall-1-2-million-cars-in-japan-over-unauthorized-checks-idUSKCN1C716O?il=0

Thanks guys!

WTB 260z Full Gasket Kit

You need vapour blasting. Talk to motorcycle resto guys. DCOE L to R: Original Glass Vapour

Hopefully when the main is reduced, the higher end of the F2 curve will lean more. Below are some general ratings and specs of E Tubes. The trend from F16 to F11 to F2 above has the tube diameter going from 8.2mm to 8.0mm to 7.5mm. This should enrich the mix as we observe. The drawing also shows F2 has the leanest low end of the 3 tubes tested. This agrees with the shape of the curves above. It is interesting to note in the hand drawing below that the F2, F11, and F3 have holes in the middle of the E tube. I think the F3 could flatten the shape even more by leaning the low rpm area. It seems this leaning also affects cruise (as you noted). If the cruise is too lean then the idle jet may need to go larger to compensate. So far from the E Tube swap experiments, the effects are subtle, and the defacto F11 and F16 tubes used in most Z's may not be optimal.

Not as big a difference in the shape as I had hoped. The biggest effect of changing E tube is like changing main jet... i.e. richness. All curves have the same hump in the middle so this can not be tuned out by e-tube. It may take fuel level or choke size. A smaller choke will cause high end richness and too high fuel level will cause low end richness. Your observations seem to match the curves: The F11 seems to be best near the start of the run (12 to 13) so you will see good power here. The F2 is the flattest. I agree with you. Please try smaller mains with F2. Hopefully the shape will change too.

F11 is slightly flatter but richer overall. F2 will be interesting. I am traveling and will post plots Friday evening. Great work to collect so fast. I am impressed.

The data seems to scale correctly now but the air is not doing enough to raise the top end and flatten the curve. I think a manufactured 240 air with 165 fuel is needed. The 160/230 is the best combo so far. Please keep the 160/230 and give the new E-tubes a spin! (Let the fun begin! )

This "fuel" is a big lie just like "speculation" of the price of gas. Govt should stop the energy cartel from these games. With global warming the winters here now start in Feb (compared to November) and they are shorter..... it should be called "spring blend gas" if they wanted to sync with the actual period where the temp is significantly lower. I wonder what they sell in Calgary where it can snow in August and you play golf in January.

Jim, I'll check in the parts barn next week.

WOW that is ingenious! Just like on modern cars but better implemented.

Could you please try the 160/230 again to rule out the anomalous data?

I did a comparison and the newest data (green) now looks normal across the rpm range. The160/230 (pink) run seems anomalous with the big hump in the middle and may not be valid. The data also shows that the 225 and 230 air correctors are too close to make a difference. I am now thinking the drilled 238 may be flowing more than a "manufactured 238". So a 235 or 240 air corrector may flatten the curve. Removing the pink data gives:

Glad you are sorted. Yes that run looks nice but as you say 0.5 point leaner will be nicer.

Great solution! Another way to skin the cat would be to cut a reverse thread into the other end to make a turnbuckle-like adjustable solution and forego the welding.

I can put you in touch with a bilingual Z nut who keeps after me to sell #249. He even gave me this mega photo he took of it before it came my way. He looked at it but did not know how special it was and missed the opportunity. Seems like an OK guy.

Verify age http://www.cbc.ca/news/canada/montreal/used-car-lien-nightmare-1.4295456

Datsun Music: https://www.youtube.com/watch?v=wUVQBC-0GOo What I used in video(Japanese Singer) https://www.youtube.com/watch?v=WZZzxS_SGHY

This thread should be of interest. http://www.classiczcars.com/topic/41332-understanding-a-weber-side-draft-carburetor-through-a-fictional-supposition/ What size chokes are in your carbs?

Fuel height is an important parameter affecting the slow the off-idle transition to the mains as well as the fuel richness when cruising on the highway. 30mm down to 27mm down are optimal for Webers. It is a critical tuning parameter. It is important to balance the fuel height with a friendly sized idle jet to get the best performance for the off-idle transition and the air/fuel ratio at cruise. The number of turns on the idle enrichment screw are not important and come after finding the best idle jet and fuel level. here is a nice blurb on fuel height: http://www.classiczcars.com/topic/44512-setting-weber-dcoe-fuel-level-with-caliper/

What 40DCOE version do you have? The later 150/151's have finer thread and the turn out at idle is usually ~ 2 turns.

All is right and good in the world again!