Patrick,
Thanks, I think that is the way we all should do it. When my engine was
on the dyno last November, the stock needle profiles seemed ok. I had
oxygen sensor bungs welded into the header collectors so the dyno guy
used two oxygen sensors for the mixture analysis. I had worried that
headers might require new profiles, but I guess not.
I have a dash mounted A/F meter I can use while driving, but haven't
spent the money for the ox sensors. Too many other more important
projects.
Ken Freese
65 BJ8
-----Original Message-----
From: healeys-bounces+ken.freese=aerojet.com@autox.team.net
[mailto:healeys-bounces+ken.freese=aerojet.com@autox.team.net] On Behalf
Of Patrick Yoas
Sent: Tuesday, June 17, 2008 6:48 PM
To: healeys@autox.team.net
Subject: Plug check technique
While I was in the Navy and stationed at Pt Mugu, Calif. in 1973/74 I
met a "civilian" guy who worked at the base hobby shop who at one time
worked for Hollywood Sports Cars and really knew Healeys. I had to
overhaul my engine and after the overhaul was done he helped me adjust
the carbs. He said that they(Hollywood), would take the cars out on the
open road and while in 3rd gear accellerate from about 35mph to 55mph
and as soon as the car hit 55mph they would turn off the engine and put
the car in neutural and coast to a stop. #2 and #5 plugs would be pulled
and the moxture checked that way. He did talk about sandpaper and
sanding down the needles a lot. Way over my head at the time. I wish I
still had those needles!!
Patrick
--- Alan Seigrist wrote:
> Ken -
>
> The SU carb needles work to very fixed mixtures at different throttle
> settings & loads... what this means is when you tune your SU carb at
> idle, it will likely not be in tune as you drive the car at different
> speeds.
>
> If you want to tune an SU carb's mixture at all different loads and
> RPMs, the only way to do it is to have a test track, a stack of
> different needles that run lean, and then drive the car around at
> successively different loads and speeds with a mobile gas analyser and
> then sand paper the needles down until you get correct mixture at all
> speeds and loads. Some people have done this with spectacular results
> in terms of mileage and power, but an exceptionally time consuming
> process.
>
> Long story short is your mechanic doesn't understand how SU carbs
> work. A gas analyser at idle is no more useful then just tuning by ear
> and using the dashpot piston lifters.
>
> Alan
>
> '52 A90
> '53 BN1
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