Folks:
With the new cam, higher compression, K&N air cleaners, etc I am
finding that the stock ZS B1AF needles are a touch on the lean side. I
get a stumble when I raise the air valve, and when I richen the mixture
the stumble gets much better, but does not go away before I run out of
adjustment to richen the mixture. I can get very close, but the needle
simply will not allow me to get rich enough.
Looking through Moss, there is a decent selection of needles
available, but I only have data for a couple of them. Here is what I
found in Moss:
Needle Idle size Comment
--------------------------------
B1AF 0.0942" TR6 Stock
B1AR 0.0931" Jag XJ6
B1BH ? Jag
B1CK ? Jag
B1CG ? Jag
B2BC ? Jag
B2AF 0.0932" Volvo
All of these are the adjustable needles for the CD2-SEV ZS carbs.
The B2AF needle was used by Volvo on it's ZS carbureted cars, and so is
available through Volvo Dealers. The B2AF is slightly richer at idle
than stock, but goes much richer than even the B1AR at cruise and
acceleration - might be good for a race motor. SAAB also used ZS for a
while, so there may be some additional needles available for/through
them. My ZS manual lists dozens of needles, but finding a supplier is
the problem, isn't it?
These needles are for the 0.100" jets. The B1AR jet is roughly 12%
richer than the B1AF by my computations (somebody want to check my
math?) at idle, assuming that the needle is 1/8" withdrawn from the jet
when the car is idling.
Here are my questions:
1. My Haynes ZS manual does not have any data on the B1BH, B1CK,
B1CG and B2BC needles. Anyone out there know where I can get some data
on them? (size, taper, etc).
2. Has anyone tried the B1AR needle to fatten the mixture? Comments
or horror stories?
3. Have others found that a mild street cam and higher compression
result in a slightly lean mixture? Were you able to adjust it out, or
did you change needles?
Any other comments on tuning the ZS carbs for a modified engine
would be appreciated.
Thanks!
Vance Navarrette
----------------
1974-1/2 TR6: 9.6:1 cr, 270/270 @ 0.390" cam,
pocket port, 3 angle valve job, K&N filters.
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