I want to change my stromberg carbs with 3 su carbs on my
1971 XKE. Any suggestions about problems I will
encounter? Thoughts about where to get a used set with
the manifold? Any help would be appreciated.–
Kailua boy
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//please trim quoted text to context only
In reply to a message from Kailua boy sent Sat 5 Nov 2011:
Kailua,
Search the E Type archives, this conversion is covered ad nauseum
in minute detail over many years. A new set is available from
Burlen that sets a price (+$3000) that the used market tries to
approach, depending on condition and buyer ignorance. Beware of
triple carb sets from Saloons, they are often hyped as suitable for
E Types to scam a higher price. To do it properly, you also need
the air filter trumpets, cannister and an early vacuum advance
distributor.
Paul–
The original message included these comments:
I want to change my stromberg carbs with 3 su carbs on my
1971 XKE. Any suggestions about problems I will
encounter? Thoughts about where to get a used set with
the manifold? Any help would be appreciated.
Kailua boy
–
PS
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Kailua boy ,
I have watched the SU vs Stromberg discussion over the years and I have yet
to see someone who runs their stock Stromberg car on a dyno before the
modification and then again after putting the SUs on. I have my doubts as
to how much improvement (if any) the SUs really provide. I’m not talking
about appearance, but actual data about more horsepower/torque delivered at
the rear wheels.
If you decide to make this modification, I hope you will do a before/after
dyno run to help add that information to the collective knowledge.
Regards,
Paul M. Novak
1990 Series III V12 Vanden Plas
1990 XJ-S Classic Collection convertible
1987 XJ6 Vanden Plas
1985 XJ6 Vanden Plas (parts)
1984 XJ6 Vanden Plas
1969 E-Type FHC
1957 MK VIII Saloon
Ramona, CA
P.M.Novak7@gmail.com-----Original Message-----
From: owner-xk-engine@jag-lovers.org [mailto:owner-xk-engine@jag-lovers.org]
On Behalf Of PS
Sent: Saturday, November 05, 2011 7:07 AM
To: xk-engine@jag-lovers.org
Subject: Re: [xk-engine] Replacing strombergs with 3 su carbs
In reply to a message from Kailua boy sent Sat 5 Nov 2011:
Kailua,
Search the E Type archives, this conversion is covered ad nauseum
in minute detail over many years. A new set is available from
Burlen that sets a price (+$3000) that the used market tries to
approach, depending on condition and buyer ignorance. Beware of
triple carb sets from Saloons, they are often hyped as suitable for
E Types to scam a higher price. To do it properly, you also need
the air filter trumpets, cannister and an early vacuum advance
distributor.
The original message included these comments:
I want to change my stromberg carbs with 3 su carbs on my
1971 XKE. Any suggestions about problems I will
encounter? Thoughts about where to get a used set with
the manifold? Any help would be appreciated.
Kailua boy
//please trim quoted text to context only
In reply to a message from Paul Novak sent Sat 5 Nov 2011:
Specifically, the triple carb manifold from the MK X or 420G
will not work, it puts the carbs too high to fit in your
engine compartment.
Based on what I have read here over the years.
P.–
Peter J. Smith, 1966 3.8S MOD
Carson City Nevada, United States
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In reply to a message from Paul Novak sent Sat 5 Nov 2011:
I did the 2 Strom to 3 SU swap on an XJ6, and my seat of the pants
dyno says there’s big difference!
Good luck,
Rob–
The original message included these comments:
modification and then again after putting the SUs on. I have my doubts as
to how much improvement (if any) the SUs really provide. I’m not talking
–
Robert Laughton www.leatheriquecanada.com 1999 Super 8
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In reply to a message from carsoncitysmith sent Sun 6 Nov 2011:
The 420G has a 1 piece manifold.
The Mark X, (at least the early ones), have 3 seperate
manifolds for each carb.
I understand the 3 seperate piece items are more versatile,
not sure whether they will fit under the bonnet of an e-type
though.
You would also have choke and linkage issues, as the HD8 are
auto choke
As others have said, the e-type archives should specify.–
The original message included these comments:
Specifically, the triple carb manifold from the MK X or 420G
will not work, it puts the carbs too high to fit in your
–
awg
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In reply to a message from awg sent Mon 7 Nov 2011:
The 3-piece Mark X manifold was for the 3.8, just like the
3-piece E-type. Also, just like the E, the 3.8 and 4.2
manifolds put the carbies in the same place, AFAIK.
But as I mentioned before, someone did use a Mark X manifold
in an E successfully–for about 10 years in fact. It’s
easy–just fit it upside-down so it points down, not up (see
archives).–
The original message included these comments:
The Mark X, (at least the early ones), have 3 seperate
manifolds for each carb.
I understand the 3 seperate piece items are more versatile,
not sure whether they will fit under the bonnet of an e-type
though.
–
Bob Wilkinson, 73 XJ6
Saint Louis, MO, United States
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Rob,
That's what I usually hear, however I would much rather see the
objective dyno data.
Regards,
Paul M. Novak
1990 Series III V12 Vanden Plas
1990 XJ-S Classic Collection convertible
1987 XJ6 Vanden Plas
1985 XJ6 Vanden Plas (parts)
1984 XJ6 Vanden Plas
1969 E-Type FHC
1957 MK VIII Saloon
Ramona, CA
P.M.Novak7@gmail.com-----Original Message-----
From: owner-xk-engine@jag-lovers.org [mailto:owner-xk-engine@jag-lovers.org]
On Behalf Of Robert Laughton
Sent: Monday, November 07, 2011 3:22 AM
To: xk-engine@jag-lovers.org
Subject: RE: [xk-engine] Replacing strombergs with 3 su carbs
In reply to a message from Paul Novak sent Sat 5 Nov 2011:
I did the 2 Strom to 3 SU swap on an XJ6, and my seat of the pants
dyno says there’s big difference!
Good luck,
The original message included these comments:
modification and then again after putting the SUs on. I have my
doubts as to how much improvement (if any) the SUs really provide.
I’m not talking
//please trim quoted text to context only
In reply to a message from Robert Wilkinson sent Mon 7 Nov 2011:
Compared to becoming a chess Grand Master or a Nobel
Laureate it’s easy, but compared to using it the right way
up and milling ang opposite angle on the flanges, not so
much. There’s a lot of ugly reverse plumbing involved and
the rough side of the manifold is shown instead of the
polished side and the linkage needs sorting. Since a large
part of the tricarb appeal is visual, installing them in a
fugly fashion seems a tad counterproductive.
Pete–
The original message included these comments:
easy–just fit it upside-down so it points down, not up (see
–
1E75339 66 Zealia D-type, 1E33100 66 FHC, 1R7977 69 OTS
Cambridge, United Kingdom
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In reply to a message from PeterCrespin sent Mon 7 Nov 2011:
Sorry Pete–I keep trotting this out because I find it so
amusing. I forgot the smiley face again.
It’s so funny because the result would be so ugly, as you
say. I wish the fellow who did it had posted a photo.
BTW, I’ll bet that the angle milling you mention might not
get you enough lowering. I was able to lower one enough for
an XJ6, but for the E you’d have to go quite a bit lower.
You might run out of ‘‘meat’’ in the flange that bolts to the
head.–
The original message included these comments:
Laureate it’s easy, but compared to using it the right way
up and milling ang opposite angle on the flanges, not so
much. There’s a lot of ugly reverse plumbing involved andeasy–just fit it upside-down so it points down, not up (see
–
Bob Wilkinson, 73 XJ6
Saint Louis, MO, United States
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In reply to a message from Robert Wilkinson sent Fri 11 Nov 2011:
Could be, but did you use the low dashpots or the taller sedan
ones? I was cleaning my MkX or 420G triple SU/manifold set
yesterday and took quite a few photos. Many sets use the dashpots
with damper tops that are a good half inch higher than the XJ/E-
type dashpots.
I agree the angle milling is a bodge and to do it ‘right’ you’d
need to fit angled washers to let the fasteners tighten onto a flat
service. I’m sorry I didn’t get a chance to try the set on the
twing-Stangleberg 2+2 I just sold.
Pete–
The original message included these comments:
BTW, I’ll bet that the angle milling you mention might not
get you enough lowering. I was able to lower one enough for
an XJ6, but for the E you’d have to go quite a bit lower.
–
1E75339 66 Zealia D-type, 1E33100 66 FHC, 1R7977 69 OTS
Cambridge, United Kingdom
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In reply to a message from PeterCrespin sent Sun 13 Nov 2011:
Pete–I had the ‘‘long neck’’ version but I cut the necks down
to the same length as the E-type version. I extended the
threads with a tap before doing so. You were the one who
(correctly) informed me that I need not modify the length of
the dashpot piston.
I agree about the washers. I relieved the casting a bit
around each mounting hole so that a plane washer sat
approximately perpendicular to the stud.
You might settle an argument about the saloon manifold–on
yours, do the runners slope slightly up (opposite of an E)
or are they horizontal. On mine, they sloped up.–
The original message included these comments:
Could be, but did you use the low dashpots or the taller sedan
ones? I was cleaning my MkX or 420G triple SU/manifold set
I agree the angle milling is a bodge and to do it ‘right’ you’d
need to fit angled washers to let the fasteners tighten onto a flat
service. I’m sorry I didn’t get a chance to try the set on the
–
Bob Wilkinson, 73 XJ6
Saint Louis, MO, United States
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In reply to a message from Robert Wilkinson sent Sun 13 Nov 2011:
Much to my surprise (having always regarded them as horizontal)
they DO actually slope upwards a fraction Bob, as you say. I assume
it’s to clear the inner wing but I hadn’t noticed the slight
upwards tilt.
Pete–
The original message included these comments:
You might settle an argument about the saloon manifold–on
yours, do the runners slope slightly up (opposite of an E)
or are they horizontal. On mine, they sloped up.
–
1E75339 66 Zealia D-type, 1E33100 66 FHC, 1R7977 69 OTS
Cambridge, United Kingdom
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In reply to a message from Paul Novak sent Sat 5 Nov 2011:
Paul the dyno test has been done by an extremely credible
source… (that is if you accept anything Lyons has to say
about horsepower. {grinning smiley face})
The XK-E is the same motor(if suitably corrected) as the
two carbed Stromberg version. The power difference is real.
They didn’t use a different block or camshafts or
whatever… Yes the distributor is different but it’s not
exactly rocket science to get the correct advance curve…
(or just swap for the correct one when you swap the carbs)…
Here’s why the 3 carbs make more power than the 2 carb
Strombergs. look at where the air needs to flow in a 2
carb… notice the curves?
Compare them with the curves in the 2 carb version… the
easier it is for air to get in (and curves are an impedance)
the more power the engine makes.
Now if you are saying that the early XK-E didn’t make 265
horsepower I’ll agree with you. However the 2 carbed version
also didn’t make 210
Want some interesting parts trivia? The stock 2 inch SU’s
flow 315 CFM (cubic feet per Minute) the 1 3/4 Strombergs
flow 200 CFM total air flow on a 2 carbed version is 400
CFM and on a 3 carbed version? 945 CFM.
With regard the later most so called carb experts will
claim that’s too much for the little engine… What they
forget is the variable venturi’s of the SU/Strombergs.–
The original message included these comments:
I have watched the SU vs Stromberg discussion over the years and I have yet
to see someone who runs their stock Stromberg car on a dyno before the
modification and then again after putting the SUs on. I have my doubts as
to how much improvement (if any) the SUs really provide. I’m not talking
about appearance, but actual data about more horsepower/torque delivered at
the rear wheels.
If you decide to make this modification, I hope you will do a before/after
dyno run to help add that information to the collective knowledge.
–
MGuar
Wayzata Minnesota, United States
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MGuar,
And the dyno numbers on a car equipped with an identical XK engine
before with dual Zenith Strombergs and after with the triple SUs on the same
exact engine were (with a drum roll)?
You could have carburetors the size of freight trains providing 66
gazillion CFM and exhaust pipes the size of the Grand Canyon, but you will
only get so much air/fuel through the engine before you reach other limiting
factors.
Testimonies that say "I could really feel the difference" when
changing over from the Zenith Strombergs to SUs do nothing for me. In G*d I
trust, everyone else please send the data.
Regards,
Paul M. Novak
1990 Series III V12 Vanden Plas
1990 XJ-S Classic Collection convertible
1987 XJ6 Vanden Plas
1985 XJ6 Vanden Plas (parts)
1984 XJ6 Vanden Plas
1969 E-Type FHC
1957 MK VIII Saloon
Ramona, CA
P.M.Novak7@gmail.com-----Original Message-----
From: owner-xk-engine@jag-lovers.org [mailto:owner-xk-engine@jag-lovers.org]
On Behalf Of MGuar
Sent: Monday, November 14, 2011 1:00 PM
To: xk-engine@jag-lovers.org
Subject: RE: [xk-engine] Replacing strombergs with 3 su carbs
In reply to a message from Paul Novak sent Sat 5 Nov 2011:
The original message included these comments:
I have watched the SU vs Stromberg discussion over the years and I have
yet
to see someone who runs their stock Stromberg car on a dyno before the
modification and then again after putting the SUs on. I have my doubts as
to how much improvement (if any) the SUs really provide. I’m not talking
about appearance, but actual data about more horsepower/torque delivered
at
the rear wheels.
If you decide to make this modification, I hope you will do a before/after
dyno run to help add that information to the collective knowledge.
–
MGuar
Wayzata Minnesota, United States
//please trim quoted text to context only
In reply to a message from Paul Novak sent Mon 14 Nov 2011:
Paul.
What are you looking for? No your 1969 2 carbed version
doesn’t make as much power as the earlier 3 carbed SU does…
That’s what Jaguar says.
Don’t feel bad… Both will easily go fast enough to get
you plenty of speeding tickets. (smiley face)
However like anything it depends. It depends on stuff like
state of tune, wear, condition, and etc. However,there is
no absolutes… But under identical states of tune a three
carb engine makes more power than a 2 carbed engine will.
As for your before and after test? It won’t provide you
accurate data
Air temp, density, humidity, etc. all effect power.
Nobody could make the swap fast enough to test in identical
air conditions… Once you understand there are no absolutes
then it’s possible to have an intelligent discussion.
You can put a dozen 3.8 XK-E 3 carbed engines on the
chassis dyno and likely none will be over 200 horsepower. OK
make it a dozen 3.8 and another dozen 4.2 But whatever
numbers they are running if properly done and adjusted They
all will make more power with 3 carbs than with 2 How much?
Some. Likely 24 different numbers…
It’s up to the owners to decide if it’s worth it.
It’s the same thing with Weber carbs… Properly done,
adjusted, with the correct Venturi’s, Idle jets, main jets,
air correction jets etc. I’d guess a set of Webers is worth
about 15 extra horsepower over the perfectly tuned 3 carbed
SU’s
But your actual numbers will vary a lot due to the air…
I’ve likely got more than a hundred hours on the dyno with
all the racing I’ve done…
Want a cheap way to test? Go to a drag strip with a
properly tuned car and another properly tuned car with 3
carbs…–
The original message included these comments:
And the dyno numbers on a car equipped with an identical XK engine
before with dual Zenith Strombergs and after with the triple SUs on the same
exact engine were (with a drum roll)?
–
MGuar
Wayzata Minnesota, United States
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In reply to a message from MGuar sent Tue 15 Nov 2011:
I certainly know next to nothing about this–so I’ll pose my
thoughts more as a question.
Wouldn’t you expect more power, and in fact better mileage
when driving conservatively, from the SU manifold than from
the Strangleberg manifold, irrespective of the carbies
attached? I’m thinking of more direct induction, with
proper runners, and with each carb feeding two adjacent
cylinders as opposed to three. Depending on the intake
pulses (determined by firing order) would you not have some
degree of difficulty in getting the right mixture to all
cylinders–more so with two carbs than with three (with
three twin-chokes being the best)?
Put another way, I would expect that thee Stranglebergs,
perhaps only 1.5 inch, on an SU manifold might compete with
three 2 inch SUs on the same manifold–but conversely that
two 2 inch SUs on the ZS manifold (even if it were cast to
accept 2 inch carbs, might not work any better than the twin
Stranglebergs?–
The original message included these comments:
numbers they are running if properly done and adjusted They
all will make more power with 3 carbs than with 2 How much?
–
Bob Wilkinson, 73 XJ6
Saint Louis, MO, United States
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In reply to a message from MGuar sent Tue 15 Nov 2011:
Great thread but I wish I could get my converted SU’s to work well
enough to even have the car tested. We have done everything and
the engine continues to start missing over 2800 rpm during
acceleration. I’m almost ready to put the Stoms back on. We have
tested everything, rebuilt the carbs, new fuel pump, new electronic
distributor, new fuel lines, plugs, wires, gas cap, etc. etc. Any
suggestions would be appreciated.–
E-Type New York State Reg
Islip New York, United States
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PIPERJACK,
How about a different coil?
Regards,
Paul M. Novak
1990 Series III V12 Vanden Plas
1990 XJ-S Classic Collection convertible
1987 XJ6 Vanden Plas
1985 XJ6 Vanden Plas (parts)
1984 XJ6 Vanden Plas
1969 E-Type FHC
1957 MK VIII Saloon
Ramona, CA
P.M.Novak7@gmail.com-----Original Message-----
From: owner-xk-engine@jag-lovers.org [mailto:owner-xk-engine@jag-lovers.org]
On Behalf Of PIPERJACK
Sent: Tuesday, November 15, 2011 6:46 PM
To: xk-engine@jag-lovers.org
Subject: RE: [xk-engine] Replacing strombergs with 3 su carbs
In reply to a message from MGuar sent Tue 15 Nov 2011:
E-Type New York State Reg
Islip New York, United States
//please trim quoted text to context only
In reply to a message from MGuar sent Tue 15 Nov 2011:
There are of course lots of factors like wear etc which
affect power output but if I understand Paul correctly by
simply swapping carbs and manifold many of those are
irrelevant because the only thing chaned between dyno runs
would be the induction system and, possibly, air pressure
and temp. It doesnt take THAT long to swap carbs over and
there’s every chance air conditions would be similar before
and after and to the extent there might be a change it can
be somewhat corrected for when analysing the readings.
Right now, in the absence of ANY real world before and
after numbers from anyone, it’s natural for people to
wonder about bang per buck even (especially?) if a dizzy
swap is also required. Far better to have some numbers and
apply guesstimated corrections for any co-factors than have
no real world present-century numbers and have to
guesstimate the whole shebang start to finish.–
1E75339 66 Zealia D-type, 1E33100 66 FHC, 1R7977 69 OTS
Cambridge, United Kingdom
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