I have obtained a manifold with triple HD8 carbs for
fitting onto a S3 XJ6 engine. The casting numbers on the
manifold are C23231-8 and SG7162. Am I correct in thinking
that they are from a mk10 / 420g
I believe that the S3 head is a straight port as is the
Mk10 / 420g so they should be okay, are there any issues or
modifications to the S3 head required to make the
transplant work
Could someone also explain what the two water hose
connections at the opposite end to the thermostat are, one
is a narrow bore one is a wider bore, and what the
connection at the thermostat end is for
Finally what is the best way to clean the inside if the
manifold including the water channels
Thanks
Howard–
Howard, Leeds UK XJ6 series 3
Leeds Yorkshire, United Kingdom
–Posted using Jag-lovers JagFORUM [forums.jag-lovers.org]–
In reply to a message from JagWaugh sent Sun 2 Oct 2016:
Hi Andrew,
thanks for the response. I am not sure what type of choke
is on the carbs, I will post a photo tomorrow if that’s
okay.
If the number on the manifold, as you say is far away from
a Mk X I wonder if it is from an early E type
In reply to a message from Leeds Howard sent Mon 3 Oct 2016:
Howard,
It’s a bit confusing to respond because you’ve posted on
several forums. Anyway, if you look at the Gallery photos
on the Ronart website you will see two examples of triple SUs.
One is a MK X 3.8 manifold; the carb bells appear to have
shortened tops, or they are from an E-type.
The other is a MK X/420G 4.2 manifold, with its normal
carbies without shortened bells.
Both have the automatic electric choke, or hisser. It
consists, in part, of the black cylindrical thingy which you
can see sitting low, between the front and centre carbies.
On the 4.2 manifold, you can see the apparently unused
temperature sensor on the top, and in front of it a blanking
plate (triangular, three screws) in the location where a
temperature (Otter) switch for the electric choke would
normally be.
You should be able to tell if your manifold resembles one of
these. If it resembles the 4.2 but lacks provisions for the
sensor and Otter switch on top, it could be an E-type.
That’s a beautiful car! What a project!–
The original message included these comments:
thanks for the response. I am not sure what type of choke
is on the carbs, I will post a photo tomorrow if that’s
okay.
In reply to a message from Robert Wilkinson sent Mon 3 Oct 2016:
Hi Bob,
Thanks for the reply. I posted on several forums as I
didn’t really know which would be the most appropriate.
Thanks for your response it was most helpful, I have
checked the photos on the Ronart site as you suggested and
the one on the red car looks the same, so I assume I have
the Mk x manifold, and I believe the carbs I have are the
HD8’s with automatic choke. is that the correct
interpretation?
I have managed to place some photos here just in case Im
wrong.
Howard–
The original message included these comments:
It’s a bit confusing to respond because you’ve posted on
several forums. Anyway, if you look at the Gallery photos
on the Ronart website you will see two examples of triple SUs.
In reply to a message from Leeds Howard sent Sat 8 Oct 2016:
Right, Howard. You are missing a metal pipe that connects
the bottom of the starting carb (threaded hole) to both of
the holes in the side of the manifold (holes are in bosses
that have a pair of threaded screw holes on each side of the
hole). Perhaps you have it already. The pipe supplies
air/fuel mixture from the starting (choke) carb to the
manifold if and only if the black solenoid has 12V applied
across its terminals. The terminals are near the top.
The rear of the manifold has a (smaller) barb that supplies
vacuum to a brake servo if present and a (larger) barb that
supplies coolant to the heater valve, if present.–
The original message included these comments:
checked the photos on the Ronart site as you suggested and
the one on the red car looks the same, so I assume I have
the Mk x manifold, and I believe the carbs I have are the
HD8’s with automatic choke. is that the correct
interpretation?
In reply to a message from Robert Wilkinson sent Sat 8 Oct 2016:
Thanks Bob,
I have the pipe you mention. Your help has been invaluable,
I will source the correct manual to rebuild the carbs. for
now I will be removing the pipe barbs, clean out the
internals of the manifold then polish it to a mirror finish
In reply to a message from Leeds Howard sent Mon 10 Oct 2016:
You’re welcome, Howard. Glad you have the pipe.
Should you disassemble the carbs before you get a manual,
it’s best to keep the parts from each one separate,
especially the piston/vacuum chamber pairs, which are matched.
Sorry, but I erred in describing the rear vacuum port. On
the Mark X/420G, that port supplied accessories, while the
brake booster received vacuum from the port on the bottom,
near the centre.–
The original message included these comments:
I have the pipe you mention. Your help has been invaluable,
Not sure if I am understanding you fully, (whether you are intending
polishing the inside or outside of the manifold) but generally mirror
finished inlet ports are not considered optimal.
See the section on porting and polishing here :
Because the air speed at the port wall is zero, there has to be a shear or
boundary layer between the wall and the high speed air flow in the centre of
the port. Any surface roughness has to be large enough to break through the
boundary layer into the high speed flow, in order to negatively impact flow.
i.e. VERY rough. Conversely, a degree of texturing can assist fuel
vaporisation, due to higher surface area. The suggestion is that 80 grit is
as fine as you want to go, however casting imperfections should be removed.
(The argument of textured walls only applies to parts of runners where air
and fuel are mixed)
The opposite is true with exhaust ports, where smoother finish minimises
heat transfer.
Port and gasket alignment is more critical, in my opinion, and has never
been a strong point on the Jag engines.
Cheers
Mark
PS. I converted a 3.4 to use triple carbs and had a lot of trouble getting
the mixture right. In hindsight, I think I had the wrong springs in the
dashpots, as the carbs were from a 4.2 and were too stiff and wouldn’t allow
the needles to lift sufficiently under load. I assume the converse is true.
I assume the springs changed depending upon engine capacity?-----Original Message-----
… clean out the internals of the manifold then polish it to a mirror
finish
In reply to a message from Mark Eaton sent Mon 10 Oct 2016:
Hi Mark,
your point is noted. I am polishing the outside of the
intake manifold leaving the inside as manufactured so that
the casting etc. allows the air mixture to swirl allow a
mix to take place.
I will be rebuilding the carbs in due course, so will
ensure correct jets and springs for a 4.2L–
Howard, Leeds UK XJ6 series 3
Leeds Yorkshire, United Kingdom
–Posted using Jag-lovers JagFORUM [forums.jag-lovers.org]–
–Support Jag-lovers - Donate at http://www.jag-lovers.org/donate04.php –
In reply to a message from Robert Wilkinson sent Mon 10 Oct 2016:
Cheers Bob
I will definitely be keeping all the parts form each carb
together, there is no point making extra work trying to
rematch parts, there is more than enough to do without
going there. I will probably get a manual on HD8 carbs
before I start–
Howard, Leeds UK XJ6 series 3
Leeds Yorkshire, United Kingdom
–Posted using Jag-lovers JagFORUM [forums.jag-lovers.org]–
–Support Jag-lovers - Donate at http://www.jag-lovers.org/donate04.php –
In reply to a message from Leeds Howard sent Wed 12 Oct 2016:
Howard,
With the exception of how to ream and replace the metal bushings I
think there is enough information available on the Burlen website
to get most people through rebuilding the carbs. See:
I think you are best to order parts straight from them.
Selecting a needle may be a bit of a guesswork. What air filter are
you planning to fit?
Andrew–
The original message included these comments:
going there. I will probably get a manual on HD8 carbs
before I start
In reply to a message from JagWaugh sent Wed 12 Oct 2016:
Thanks Andrew I will check out their site. I agree its best
to go and get parts from them, I understand they have taken
over from su.
As for the air filters I haven’t got around to details but
I would like to fit individual trumpet or ram type as I
think they would suit the style of the car.