Paul: I've had reasonably good luck with M70 in the Prozac, Preparation H,
Rogaine, Viagra Automobile City Datsun (currently under repair after getting
T boned -- twice -- at the Jefferson 500), but the best bet is probably the
.010 jet and SU needle combination as per Sharp, Wessel and Drews.
This is probably some overkill, but here is a portion of my carb. notes for
roadsters:
Fred Sisson http://www.team.net/www/morgan/tech/tuning.html
There are 354 needles listed for (the most common) .090 jet SU carbs. Your
particular car will probably run lousy on 40% of them, OK on 30%, great on
20%, really great on 5%, and kick butt on 5%. No wonder so few people change
needles. Where do you start? . . .
SU needles taper and the taper is very specific. All 354 needles for the .090
jet are different according to taper. SU needles each have a number/letter
designation which is of little value unless you know just how the needle
taper is contoured. There are really very few needle designations among the
300+ that are "progressive" in any way. You consult the chart & compare
numbers. The SU needle chart shows diameter of all 354 needles at 1/8"
intervals. Each 1/8" increment is a "station," starting with #1 (thickest
diameter) and progressing down the needle. Stations 1-2 are idle and are the
same for most needles. As you progress up the stations (down the needle), you
affect off-idle, low midrange, high midrange & WOT (wide open throttle).
Smaller diameter is richer; there are 12 stations per needle! There is a lot
of tuning potential there.
Here's how needles are listed. Numbers are needle diameter at 1/8" increments:
NOTE:890" is Station 1; Diameters are from shoulder to tip of needle. (NOTE
.890 = 0.0890" diameter?)
AH .890 .862 .830 .803 .775 .756 .733 .711 .690 .670 .650 .630 .610
AH1 .890 .860 .820 .790 .765 .750 .730 .710 .690 .670 .650 .630 .610
(Compared to AH - richer in midrange)
AAM .890 .850 .824 .785 .752 .715 .673 .630 .590 .567 .543 .519 .496
(Compared to AH - much richer)
AI .890 .850 .817 .798 .780 .765 .750 .732 .712 .693 .685 .675
(Compared to AH - richer low-mid range progressing to leaner high-range)
Nestor Moya (Email unknown) measured Hitachi M39, M43, M66 needles at 0.1"
stations and averaged the measurements of each pair of needles (NOTE: Sample
size is very small, n = 2 of each needle). Moya's measurements vary from the
1600 cc needle chart in Honsowetz's How to Modify your Nissan/Datsun OHC
Engine. NOTE: Not directly comparable to the 1/8" stations used to measure
British SU needles.
Needle Measurements (NOTE: 902 = 0.0902")
0"
.1"
.2"
.3"
.4"
.5"
.6"
.7"
.8"
.9"
1"
1.1"
1.2"
1.3"
1.4"
M39
0.0.902
0.0871
0.0847
0.0823
0.0804
0.0784
0.0769
0.0760
0.0751
0.0735
0.0713
0.0688
0.0671
0.0653
0.0639
M66
0.0898
0.0884
0.0873
0.0853
0.0828
0.0808
0.0784
0.0760
0.0733
0.0718
0.0703
0.0688
0.0674
0.0658
0.0642
M43
0.0905
0.0873
0.0849
0.0828
0.0805
0.0788
0.0771
0.0761
0.0759
0.0732
0.0713
0.0689
0.0665
0.0654
0.0646
Datsun (Hitachi) Needles List fewer "stations" than British SU needles:
M-66 (16354-22011) 0.089, 0.087, 0.081, 0.074, 0.0685, 0.064
M-83 (16554-H2316) 0.088, 0.0875, 0.0815, 0.0755, 0.070, 0.0625
M-70 (16354-A7710) 0.089, 0.088, 0.082, 0.074, 0.068, 0.060
M-43 (16354-15810) 0.091, 0.0875, 0.081, 0.075, 0.0695, 0.0665
M-39 (16354-14610) 0.090, 0.088, 0.082, 0.076, 0.071, 0.062
M-76 (16354-A8710) 0.088, 0.087, 0.081, 0.074, 0.069, 0.0635
M-73 (16354-E3210) 0.0885, 0.087, 0.081, 0.075, 0.070, 0.065
M-87 (16354-H6000) 0.0875, 0.086, 0.080, 0.0735, 0.0685, 0.063
M-6 (16354-16710) 0.0895, 0.0875, 0.082, 0.076, 0.073, 0.070
M-26 (16354-10400) 0.090, 0.088, 0.0825, 0.078, 0.072, 0.064
M-15 (16354-12210) 0.090, 0.088, 0.0825, 0.0775, 0.072, 0.0635
SU RH 0.100, 0.095, 0.0878, 0.078, 0.069, 0.057
SU RF Unknown
The richest Hitachi needle above is M-70 (?); apparently used (optionally?)
on late model, smogged cars. The next richest(?), M-39 was the early stock
1600 needle.
M-43 was a "high altitude" needle option, one of the leanest.
Honsowetz mentions the SSS but doesn't discuss the needles for the 38 mm
Hitachi SU. Neither does Bob Waar.
Bob Sharp used .100 jets and SU RH needles for racing
Bill Wessel uses .100 jets and SU RF needles for racing.
Jack Drews uses .100 jets and SU RA, RB, RC, and SS needles in his HS4s for
racing.
Drews notes, "These things are so pointy on the end I'm afraid I'll injure
myself handling them. I am also running the adjusting nuts eight turns down!
Car accelerates fine, but on long straightaways it doesn't have the same
power
as in the past (with Strombergs), and EGT has climbed to 1500 deg.F."
Smogged engines had an auxiliary air inlet in the intake manifold,
which leaned out the mixture when using rich needles.
E. Some Sources of Needles, etc.
Seven Enterprises
Newport News, VA
Greg Solo's Engine Room
Santa Cruz, CA
Tel. (831) 429 1800
Burlen Fuel Systems, Ltd. info@burlen.co.uk
Ztherapy www.ztherapy.com/
Good luck,
JH Bahn
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