Folks:
After nearly 3 months of waiting, Moss finally delivered my
second B1AR needle (originally in the Jag XJ6). Recall that I had
modified my engine, with a 270 degree duration cam, 9.6:1 compression, 3
angle valve job, pocket ported, K&N air cleaners and stock exhaust.
Well, I could not get the mixture to come in, although I could
get close. So I gave up, and got the needle charts from Burlen
(www.burlen.co.uk) to see what a better needle might be.
Turned out that the B1AR needle was available from Moss, and is about
10% richer than the stock B1AF needle, so I ordered a pair.
Installation was temporarily delayed because the Jag needles are
non-adjustable, and my 74 uses adjustable needles. I had to cut apart
the B1AR needle carriers using a fine file to extract the needles. This
took about 3 minutes per needle. I then used a pair of miniature needle
nose pliers to wiggle the pin out of my adjustable carriers, swapped the
needles, and reinstalled.
The mixture dialed right in using the "lift the slide" test,
although I still had to go about 1-1/2 turns rich to get the mixture
correct. At least I could now dial in the mixture, which is a lot more
than I could do before. Prior to this, the engine would stumble, and
going to the full rich adjustment would only make it better, but not
cure the lean condition. Now when I lift the slide 1/16", I get the
sweetest little blip in RPMs before it settles back down.
I took the car for a long drive and it ran great, noticeably
smoother at idle. I pulled the plugs when I got home, and they are
pretty much spot on for color, being a light cardboard color (tan-grey)
with light uniform deposits.
Overall, I would call the needle swap a success and I would
imagine that the car makes more power now as well, although using the
butt-o-meter as a dyno is notoriously unreliable. It SEEMS slightly more
powerful, but what do I know? It is noticeably smoother however, and the
plug color and idle mixture look good. Something that was not true
before.
If I was going to do it over, I would go even a bit richer than
the B1AR needle, to get the mixture adjustment centered. I would imagine
that this would be about 15% richer.
If you have modified your motor, I recommend that you consider
swapping needles to get your mixture back to par.
Cheers,
Vance
P.S. for those of you in the Northwest, the All British Field
meet is next weekend at Portland international raceway. See you
there....
Check out the new British Cars Forum:
http://www.team.net/the-local/tiki-view_forum.php?forumId=8
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