I would agree with what both Pete and Mguar has said. Having said
that though, it shouldn’t be assumed that Webers are a troublesome
exercise…IF…you have access to said dyno, the expertise to
read the results and access to the variety of jets.tubes etc you might
need.
My own E had them on it when I got it so it wasn’t choice for me.
However, over the years I could never get it just right! I didn’t
have access to a dyno anywhere near my home so I decided to just
muddle through with them. They ran ok, started just fine (no choke
required), got decent fuel economy and over the years I kinda got hard
headed about those who tried to tell me that SU’s and even the Stroms
would run just as well.
Finally, earlier this year (maybe late last year…memory) I decided
to put the car back to original as far as carb’s and air-intake went.
I made mod’s to the manifold by removing the secondary throttle plates
and fine tuning the manifold internals for good smooth airflow from
the secondary to primary manifolds. Rebuilt the original Stroms,
fitted a new choke cable and bolted it all on.
The result has been surprising. The car runs just as good as it did
with the Webers and revs higher. This is probably because my Webers
weren’t tuned quite correctly, per my earlier comments.
Purpose of all this narrative…if you want more performance then
know that if you use the Webers, you really need to make some changes
to the engine internals to take advantage of them, otherwise, imo, the
hassle isn’t worth it.
If you want just eye candy and like the induction roar of more or less
open induction pipes, then the Webers are for you.
Beyond the Jag, my experience with Webers was from the Lotus Elan and
Europa and Lotus Cortina of years ago. Also a couple of Ford Anglias,
and a mini and MGB. All these cars ran just fine but it took a lot
of work (not with the Lotus as it was original equipment) to get them
right.
You have been warned…:-)On Tue, May 31, 2011 at 1:08 PM, r1_pete pcongreve@sky.com wrote:
In reply to a message from old jag man sent Mon 30 May 2011:
I agree 100% with McGuar, a rolling road session is needed for
optimum setup, however, a basic setup to get you going, assuming
DCOE 45 Type 9’s - chokes 38mm, 150 mains, f2 emulsion tubes, 180
air correctors, 45 pump jets, 45 idle jets, 7.5mm float height.
A quote from Des Hamill’s book,‘No modified road going engine needs
more than twin 13/4 or 2 inch SUs’ One reason I removed my Webers
and fitted a Stromberg manifold with twin HS8 SUs.
Don’t forget also, you have the emission control distributor
advance curve assuming the original distributor, S3 XJ6 electronic
is considered a good replacement. I went 36 - 1 trigger wheel and
fully mappable advance, which is also an advantage with webers and
no vacuum advance/retard, as you can use a throttle position sensor.
Check out my photos for weber and SU installations.
The original message included these comments:
I have searched the archives for the correct jetting etc. to
suit a stock 4.2 XK fitted with Webers.
–
r1_pete
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