Darrell,
I am very interested in this as well. I have a pinging or
knock under acceleration on my HS6 equipped TR4 with a
TR4A engine. I was told by the TRF mechanics last Summer
that it can be caused by a lean mixture. I switched to the
SW rich needles and carefully centered the jets.... it
definately helped a lot but... it is still there.
I rebuilt with the 87MM piston set and the head got a lot
of work. I don't know what my CR is. The symptom does
not occur until the engine comes to full temp and can be
made to go away with the choke.
I assume it could also be caused by a sharp edge in the
head where the valve inserts were done.
Please keep us informed about your progress
Brian Sanborn
1962 TR4
On Thu, 29 May 2003 20:07:05 -0700
Darrell Walker <darrellw@ipns.com> wrote:
>I'm trying to decide what needle to try next in my SU HS6
>carbs on my
>TR4A. Currently I'm running the "rich" needles (SW).
> According to
>both the "seat of the pants" method, and an O2 sensor,
>I'm running a
>somewhat lean starting at about 2500 under heavy
>acceleration, and very
>lean above 3500 under any acceleration. Pulling the
>choke, which drops
>the jets about 1/4" (two stations) smoothes out the
>missing, but
>according to the O2 sensor it is still a little lean.
> Above 4000 or
>so, even with the choke out, things lean out again.
>
>Using SU Search, I'm thinking of trying something like an
>RR, RV or RH
>needle. They are all about 2-3 stations richer above
>"low cruise",
>which seems to correspond to what using the choke
>indicates. Any flaw
>in that logic?
>
>Alternatively, can anyone recommend a needle for an
>engine with
>following:
>
>Mild comp cam
>K&N filters
>1.5:1 roller rockers
>87.5 mm pistons
>C/R calculated to 9.25:1
>Headers
>
>(there is more done to the engine, but I think that is
>all that is
>relevant to needle selection).
>
>Lastly, does anyone know of a good source for SU needles
>on the US west
>coast? I know that Joe Curto carries a large selection,
>but I'd like
>to save a few days on each cycle (I'm guessing it will
>take more than
>one try to get a good fit).
>
>Ultimately, I might try tuning the needles myself, as
>outlined in
>"Building and Power Tuning SU Carbs", but I want to get
>to a standard
>needle that is a bit closer to correct first.
>
>-Darrell
>--
>Darrell Walker
>66 TR4A IRS CTC67956L
>Vancouver, WA, USA
/// triumphs@autox.team.net mailing list
/// or try http://www.team.net/cgi-bin/majorcool
/// Archives at http://www.team.net/archive
|