Why not?
I’ve already removed the butterflies…i didn’t find the wired open solution professional.
But why not just remove the damn thing, make a tube/hose solution to bypass the water jacket, use smaller studs on manifold and attach carbs dorectly to intake?
Eliminate the whole damn thing…
I’ve read both ppl doing it, no problems, and others stating no as it messes up internal crossflow of intake airflow…
??
I can’t see why it would be a problem…no earlier cars had them?
I asked the same question, The response I got was the (water) heat is needed to enhance the atomization of the fuel as it enters the engine. Or to help from the fuel pooling in the intake runners.
I’ve got two Xj6’s Series II and III that phenomena carried on until death of the XK6.
**
The secondary manifold and the use of the Strombergs was a further attempt to improve economy and increasing emission demands, Demian - it does engine performance no favours…
Frank
xj6 85 Sov Europe (UK/NZ)
**
so what I was told is incorrect? so we can do a way with the secondary manifold and reconfigure the head cooling & thermostat housing bits, Right? Or, the easy solution to remove the throttle / butterfly valving, plug the holes on the secondary manifold? Not that I’m going to do this immediately; but if the engine comes out, its an option I guess. maybe increase performance a bit.
I’ve read the history on the XK6 engine and it is capable of making power, being reliable, and running very smooth. I have an extra one of these in the garage, that (when I get the other cars sorted) It would be a fun project build the engine to its optimal configuration. I’ve read that just simple tweaks like Port polishing, gasket matching, and flowing the head can make an 50 to 60HP improvement. which is significantly noticeable.
I have a lot of grandious plans.
**
While the mentioned attention to air passages are commendable, Mark - they will not yield power increases of the magnitude you mention…
…but in conjunction will an engine overhaul it is well worth the minimal effort required. The full monty would include balancing of all parts - and get rid of the Strombergs. They are designed for economy and emission control, not power - double or triple SU offer more. Just removing the secondary manifold and retaining the Strombergs is neither here nor there. Mind you; the Strombergs are very good carbs and well worth keeping in full working order - .messing with the secondary throttle housing may seem to simplify the set-up, but that is all…
Frank
xj6 85 Siov Europe (UK/NZ)
**
I’ll just complicate things.
Water heated manifolds go way back in other critters. Some were a way of substituting from exhaust heated intake manifolds. In earlier days, cold engine drivability. A bit counter intuitive as
the water that was intended to heat the intake was cold when heat was desirable???
The LT! engine in my 83 provides for water to the throttle body. But, this is an emission issue. Some counsel a bypass for added power. In theory, true, a cold charge is more dense.
But, I’ve chosen not to mess with it. More than enough power and it runs just fine.
Tuned ports. Removal of the secondary throttle manifold
in this application shortens the port. Lots to research here.
The space between the carb mouth and the wing wall is tight.
So, SU’s minus the stock air box and forward snout might benefit from more space. Think “tunnel ram” intake manifolds. Object, longer ports from carb venturys (sp), to valve pocket.
More power, for sure. Low speed drivability, typicaly an issue.
Conclusion: Sounds like a lot of fun for a project, not so much for a daily driver…
Carl,
Nice post and great info.
Thx for taking time.
Personally, my interest was not performance, per se, as much as eliminating emissions nonsense and cleaning things up in a purist sort of way.
Although of course a performance increase would go hand in hand w this and appreciated.
I’ve removed the butterflies entirely, just leaving the rod.
Ppl talk of wiring them open, but i don’t like that idea at. Not thorough/proper/professional…
Intend to remove rod entirely and plug holes at bushings.
Need to remove entire intake manifold anyway to degunk and detail everything, but still may consider removal of intermediary manifold if not too much trouble.
Mine has that egr at the rear, with that aluminum cap w hole it attaches to.
I need to find elegant solution to cut that tube off and plug the hole, perhaps threading it and using brass plug or something from Elliott’s (specialty hardware store in us for those abroad)
would be nice to find an eu cover without the egr or earlier car as my 68 etype had or triple setup from mk10 420g…
…but alas, yes, so many ideas and dreams to get carried away with.
I have such perfection in my head.
PS. Never thought of or heard of use for atomization…kind of counterproductive then the continued talk of and searching out of methods of cold air induction, and relocating intakes, etc.
Yes, these mk enough power with Strombergs, especially with the s3 xj6 head…and are more stable in my experience.
On the 3.8 mk2 i had i was always having to address something, on the s1.5 e type,never touched them once…not one time in all those years and after head gasket replacements, driving daily, etc.
**
Other things being equal, Demian - it’s the amount of petrol burnt that generates power…
To burn petrol; air (or rather the oxygen in the air) is required - and for complete combustion 14,7 parts air to 1 part petrol, by weight, is required. However, as contact with air is required for burning - petrol burns on its surface. As there is but short time for burning available in an engine - the droplet size is not negligible, and carbs delivers droplets. The use of ‘choking’ for a cold engine serves an essential function; fuel tends to condense on cold surfaces - fuel is ‘lost’, countered by fattening mixture to ensure enough fuel enters the engine. As the manifold heats up, or rather, the heating counters the fuel cooling of the manifold. Point of this is that excess fuel is ejected through the exhaust unburnt - wasted, producing no power…
Arguably, the gain of heating the manifold improves droplet size - the ideal would be fuel vapour, small droplets. Which is the point of the better mechanical atomization in injected engine - or indeed in diesel engines. Carb heating plays little part in this; the main purpose is to prevent carb icing - the high air speed through the throttle lowers the air temp, air humidity freezes out, blocking the throttle…
As an aside; cold air is denser, weighs more - and can therefore burn more petrol. So cold air is good for power as the volume of air entering the engine is almost the same. The purpose of the turbo intercooler counter the heating of compressing air - and caters for increase in air weight…
Frank
xj6 85 Sov Europe (UK/NZ)
**
Thank you for that…
Perhaps I am being wasteful and need to simply click on the 
or whatever…
Hello all, I recently join this forum and my reason to join this forum is that I’m also a big jag lover. I really like jaguar and I think this forum will help me a lot to increase my knowledge regarding jaguar.