Secondary Throttles on Stromberg Federal TCSs.

[Bryan Boyle]

Question:

Loose and block off the shaft openings (removing the levers and bits from the carbs to actuate)?

or

Keep?

(as an aside, before removing the carb stack this afternoon, measured the clearance from the adapter plate to the secondary body...there was NO gap; the thackery washers were torqued down tight.  O-rings in the secondary body were hard as a rock (the front carb had orange RTV around the ring...uh, no.  Not proper.  Replace the damn o-ring, don't goop up with RTV.  Damn DPOs.)

[Kendo]

Mine had the secondary shafts and butterflies removed. It reduces impediments to airflow, and the shaft holes are probably easier to seal than the shafts.

Just my two cents. It's also been suggested to flip over the secondary manifold to produce a sort of Euro-style high balance tube manifold. But I haven't really evaluated that.

[Grumblebuns]

I suppose you could try to remove just the butterflies themselves if that is possible and keep the shaft in place but then the shaft holes could be source of air leakage past the shaft. It might be simpler to totally remove the entire secondary butterfly assembly.

Ken, thinking about your idea to flip over the inlet manifold to create a balance tube effect. I believe with the stock setup in place, and the butterflies closed, the air/fuel charge enters the bottom  passage in front of the butterfly, and exits the inlet manifold into one of the crossover tubes over to the exhaust manifold back to the other crossover tube and back into the inlet manifold and exits behind the closed butterfly. Most owners just block off the crossover tube passages on the inlet manifold. Can somebody explain how a balance effect is created with the crossover pipes blocked off? I should probably look up the system in the manual.

Thinking it over, it appears that both passages connect internally maintaining the balance.   

[Kendo]

I still meant to remove the butterflies and shafts, and close off the crossover tube opening. With all of that done, I think the two carb throats are connected by a balance tube that runs along the bottom of the casting. So, rotating it 180 degrees would put the balance tube on the top. I haven't done this. I just read about it (probably here) and thought it would be worth looking into the next time I have the carbs off.

[Bryan Boyle]

Mine had the secondary shafts and butterflies removed. It reduces impediments to airflow, and the shaft holes are probably easier to seal than the shafts.

Just my two cents. It's also been suggested to flip over the secondary manifold to produce a sort of Euro-style high balance tube manifold. But I haven't really evaluated that.

so what would be the advantage to that (besides eliminating perhaps a locus for the fuel to puddle (fwiw, the cross over tubes were deleted and the mounting flanges blocked off at some point in the hairy past on this car...).

[Grumblebuns]

You can flip the secondary manifold over but Stromberg mounting points are also flipped over causing the Strombergs to be mounted upside down. As you said, the down side of low balance passages is the pooling of fuel in the passages.

[Bryan Boyle]

Which would mean flipping the plates that the strombergs are mounted to, also.  wonder if that would work...IE would the intake line up...etc. 

[Bryan Boyle]

Of course...there is this which got me thinking...but may be too much carburetion for this engine, since it's set up for a TR6...but nice thing about webers is that they are almost infinitely changeable...lol.

[TurboFource]

That looks like an awful intake design...didn't someone on here have those and swap to Mikunis?

[pboedker]

Would it be possible fill/block the lower holes in the secondary manifold in addition to removing the shafts and blocking those holes? 
Then only the upper tube in the manifold is connected from side to side, just as you're requesting.
Or am I missing something (probably)?

[Bryan Boyle]

Would it be possible fill/block the lower holes in the secondary manifold in addition to removing the shafts and blocking those holes? 
Then only the upper tube in the manifold is connected from side to side, just as you're requesting.
Or am I missing something (probably)?

Nice seeing you again, Peter!  Hope all is well!  You know I post dense text when I'm working on a project, and this one is pushing the envelope for me in new directions...

Was just spitballing (poking a stick in the cage?).  Have the intake down to the head flanges all apart...finding all sorts of DPO happiness (like no nuts on the 2 bottom studs holding both of the carbs on the adapter plate to the secondary throttle assembly), copious amounts of RTV squeezed out of joints, thackery washers torqued down tight, idle trim screws set vastly different between front and rear carbs, 2 different tapered needles (I have their mates in a box of spare parts...) in the pistons...So...back to 'stock' (except for the lack of secondary throttles) and set up per the book.

Have cleaned up the threads on the pile of 5/16x24 nuts, ran a die down all the studs to clean up those parts, have a stack of new split and flat washers to use where needed, new thackery washers, new gaskets, new diaphragms, new o-rings, new floats, new needle valve, a gallon can of carb dip and a couple parts brushes.  Time to dig in, clean up, rebuild, and reinstall...

[Grumblebuns]

Would it be possible fill/block the lower holes in the secondary manifold in addition to removing the shafts and blocking those holes? 
Then only the upper tube in the manifold is connected from side to side, just as you're requesting.
Or am I missing something (probably)?

Peter, it possible do just that. Blocking off the two bottom holes in the secondary manifold appears to just leave the upper passage and openings at the top of the manifold connected for balancing the two throats. The photo shows the back of the manifold with the upper return back to the manifold exiting at the top.

I'm starting to wonder if the the pooling of fuel in the low balance tube manifolds has some truth in it or it's just a potential problem that might happen. Most TCs back in the day and even now have the secondary butterflies removed and the cross over pipe opening sealed up. The upper and lower openings in the throat of the manifold were left open. Has anyone heard of these modified manifolds giving carburation problems due to pooling of gas in the lower passage and the symptoms? My TCS was left in that state for years and may be I was too ignorant to know I was having issues.

[pboedker]

It's good to see you've also found this forum, Bryan. Things are going fine over here in Denmark, thank you. 

The TwinCam will keep you occupied for a while. But I guess that was always the plan. 

Time to dig in, clean up, rebuild, and reinstall...

While you are inside the Strombergs, remember to adjust the temperature compensators equally. Whether they are always shut or working is not so important, if they just work the same/balanced way on both carbs.
And consider having the plugs in the bottom of the fuel bowl welded. I assume your carbs are adjusted by the needle from the top, and eliminating 2 o-rings between the fuel bowls and the ignition parts below can't be a bad idea.

[pboedker]

Peter, it possible do just that. Blocking off the two bottom holes in the secondary manifold appears to just leave the upper passage and openings at the top of the manifold connected for balancing the two throats. The photo shows the back of the manifold with the upper return back to the manifold exiting at the top.

The previous owner of my Europa had the secondary manifold replaced with the UK/Stromberg high balance tube manifold along with distributor and carbs updated to UK specs. So I never had one of these original secondary manifolds with butterflies and all. It really is an interesting contraption. 

[Kendo]

Those UK high balance tube manifolds are hard to find. I've been looking for one.

I thought the pooling of fuel problem in the US manifolds had to do with the manifold catching fire if there was a backfire or something, not that the pool caused variation in fuel/air ratios. It's all starting to sound like some legend whispered in the back rooms, than anything based in fact. (After that, I should probably go get my Nomex coveralls  )