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Intake Manifold Oddity

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RDKeysor

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My 1960 Series 1 3000 has three fixtures mounted atop the intake manifold. Their purpose is a mystery. Each of these fittings (see attached photo) plugs into the cast-in boss found on these manifolds between each of the three intake manifold entries to the head. I've seen pictures of these bosses both with holes (I assume they don't penetrate into the manifold) and without holes. In my case, each of these holes has a 5/8" diameter fitting with an attached tube projecting from one side. In each case this tube has a small section of rubber hose slipped over it, the hose blocked at the other end by a small bolt. The fittings each project about 5/8" above the manifold, The base is 9/16" in diameter, 3/8" long, and appears to be a slight taper. The bottom of the hole in the manifold has two 3/16" holes each appearing to be angled into the manifold, one toward the cylinder at right, one to the cylinder at left. The former owner, his mechanic and the person who restored this car profess no knowledge of these fittings. The only thing vaguely resembling might be the "balance tube" seen on pictures of tri-carbs. This is not a tri-carb. Also, this car has an aftermarket stainless steel exhaust system that produces a pronounced exhaust popping under deceleration, and I suspect this is enhanced by the communication that exists via the holes into the manifold. I intend to attempt to plug those holes and reinstall the fitting shown. But the question is, what do we have here? rsz_dsc00398.jpg
 
Don't know the reson behind these plugged holes except maybe a way to balance carbs during tuning. If they do not leak, I'd leave them for tuning with balance kit or gas analyizer. The popping under decel is normal for open stainless systems. It's just the rich fuel snapping on closing of the throttles, which is why we buy these style exhausts. You might lean fuel but popping might increase or check vacuum advance to be sure it's not killing ignition for a backfire. Love my stainless system have sold many just from the decel sound.
 
Maybe your manifold had a thermal electric choke instead of the cable. There would have been a small auxillary jet to add extra fuel at start up.
Bob
 
My guess would be for vacuum balancing with a meter. With the exception of the bosses, is that an ordinary manifold for two carbs?

What carbs have you got?

:cheers:

Bob
 
This is a two carb car. My search for an answer to this puzzle had considered the "balance tube" found on tri-carbs. Perhaps this was an attempt to emulate whatever advantage that tube brought to the tri-carb, but I haven't seen anything in the literature about the function of that device. This was clearly a professional installation that seems to have been abandoned when the tubes were blocked with the installation of a bit of rubber hose plugged with a bolt. I think the choke is the standard variety.
 
IIRC, the tri carbs have three individual manifolds that are connected only by the balance tube. As your car has a log manifold already connecting the carbs, I can't really see what advantage an additional balance tube in the manifold would have. Nonetheless, I'm stumped over these fittings as well. The only other thing I can think of is a tap for a vacuum source, like a brake servo, but I can't see why they would need three of them. It's a puzzlement, alright.
 
Wow I thought that I was the only one with those three tubes, I have a 60BT7 ,that dad purchased back in 70' he was always doing something different , I really thought that this was his doing, and I often wondered what these were for. I would post pics but don't how to do it from iPad
 
British_Recovery said:
The manifold is probably for the " Auxillary enrichment device ".
Click to expand...

I think you're right. Per Anderson-Moment: "The auxiliary carburetor was connected to a thermo switch installed in the top of the cylinder head at the left front corner. When the engine was cold, this carburetor was open and injected gas directly into the intake manifolds through three black rubber pressure hoses."
 
I initiated this discussion. There is currently no "auxillary enrichment" device on this car. I had a starting carb on Jag MK2, so I have some familiarity. Hopefully someone can tell me where in the Healey literature such a device is discussed, as I haven't seen anything of the sort (I am a novice on Healeys, though I had one out of college in 1963) in my reading. Frankly, I also don't know anything about the "balance tube" that is pictured in the factory shop manual, but not discussed. One thing is certain, this was a professional installation that it seems likely one of this car's many owners chose to block off at some point. Appreciate the many responses to my query. I do want to modify and minimize these fixtures, but the car runs well and I don't want to screw it up without knowing what this is all about.
 
Regarding popping on deceleration, I had that symptom when the connection of the exhaust manifold to downpipe loosened. I put in new copper sandwich gaskets and used brass nuts on the manifold studs which do not come loose. This cured the popping, which is caused by air being sucked into the exhaust through the bad seal and allowing the raw fuel to burn in the pipes.

 
RDKeysor said:
I initiated this discussion. There is currently no "auxillary enrichment" device on this car. I had a starting carb on Jag MK2, so I have some familiarity. Hopefully someone can tell me where in the Healey literature such a device is discussed, ....
Click to expand...

On page 89 of Anderson & Moment; Austin Healey Restoration Guide; "An "automatic choke" was tried on 29D engines in 1959 from E.29D/2864 to E.29D/6369. These cars had no manual choke, but rather had a small auxiliary carburetor maounted between the two regular carburetors, similar to those on the Jaruar XK engines. ... This mechanism proved undependable and was deleted on most engines as E.6369 and on all engines at E.6395." These cars were built between April and November 1959.
 
My car has a manual choke. The diversions about auxiliary or starting carbs are interesting, but they don't have any bearing on the issue i raise, still unidentified fixtures mounted atop and drilled into all six intake ports. These things were clearly professionally made. But by whom, and why?
 
I don't think the thermo carb discussion is a diversion, but is directly the point. Your car may have a manual choke now, but at one point it had a thermo carb. When it eventually failed (as apparently many did) it was removed and replaced with a manual choke. I have not seen a thermo carbed car so am basing this on supposition and the info in the Anderson-Moment resto guide. Notice the three holes in the thermo carb picture here:

2ugyxqo.jpg


I imagine the three black rubber tubes connect these three holes to the three holes you have in your inlet manifold. Notice the Anderson-Moment reference I made above that mentions the three rubber tubes that connect to the fittings that shoot gas into the inlet manifold. When the thermo carb was activated, it would direct the enriched mixture right into the manifold to assist in starting. These fittings in your manifold are there because they were factory installed. When a previous owner ditched the thermo carb he was left with three holes that would allow plain air into the manifold so the black rubber tubes were plugged with a bolt. My guess is if you wanted to dispense with the fittings and you aren't concerned with originality you. could find a threaded plug or appropriately sized bolt and tap the holes in the manifold Again, I've never dealt with a thermo carb car before, so I could b e wrong, but this is the only explanation that makes sense to me.
 
The auxiliary carburetor fed into those fixtures using rubber hose. The reason they look professionally made is that they are factory original. You may also notice a small well at the top front of the head for the temperature switch. It may be covered by a plate now.
 
In case anyone is interested, I have a pair of these early carburetors, one of which is the thermo carb that I would like to sell. Send me a private message if you would like more info.

Richard
 
I think the answer provided by Rick and seconded by others has correctly identified the "oddities" on my car's intake manifold, and I want to acknowledge that and thank everyone for their contributions to this exploration. I think it is a measure of the viability of this AH innovation that it seems to be little known, and that my examination (via eBay and Hemmings) of a great many engine bay photos didn't come up with anything similar to my car's installation. For the moment I'm going to leave the fittings in place, though I am tempted to cut off the small projecting tubes and plug the holes with headless Allen screws so that I don't have those goofy rubber hoses hanging off them. I am curious about the possible influence of the "communication" between adjoining cylinders because of the open holes beneath the fixtures and the wisdom of somehow blocking them. I'm not interested in taking off the head so that I can drill and tap plugs for the holes without the risking getting thread cuttings in the intake system. I guess it's a measure of my knowledge that I was unfamiliar with the Anderson-Moment restoration guide, but this is how we learn. Someone tells us. Thanks.
 
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