V 12 Air Filter Housings

Michael Herlihy · Post by **Michael Herlihy** » Fri Dec 18, 2015 6:13 pm

I have a 1973 V12 Convertible that has suffered an engine fire in the region of the O/S air filter housing. Over the last few months I have managed to reinstate pretty well everything and the car now runs. Unfortunately the fire was fierce enough to melt both pairs of the aluminium blocks that the mounting bolts pass through to secure the air filter housing to the carbs. These assemblies each consist of two halves and receive the balance pipe T Bar that is connected externally via the pre formed steel pipe to the front intake pipe of the airbox. As far as I can determine they serve to balance the ambient air available to the diaphragm chambers on the carbs.
Needless to say these parts are not available from the usual sources. I also need the 'AC' temperature control valve that sits in the filter housing between the carb intakes and operates the hot/cold air flap at the front end of the airbox.
Anyone out there know of a source? Perhaps someone has converted to Webers/Injection and has the original parts lying idle? I live in hope!

vee12eman · Post by **vee12eman** » Sat Dec 19, 2015 12:38 pm

Hi Michael,

I am not sure whether you need all these items on all models/markets, so probably best if you tell us a little about your car, plus it would be nice to now a little about yourself, we're a friendly bunch but like to know a little about those we help out and ask help of.

Have a look at the parts catalogue, if you don't have one, there is a copy in the forum knowledge base and the section you need is here:

http://dl.dropbox.com/u/8496016/S3%2004 ... System.pdf

Identify the part numbers you need and ask for them that way, then we will be sure what you want.

If the castings are the parts I think they are, I don't have them on my early UK spec car and I don't think they are necessary, but as I say it depends on the exact market, date and therefore specification of your car.

As to the "AC" temperature control valves, these are available from SNG Barratt - I bought them recently but if I recall correctly I had to ring them up and they had been superseded by another model which was similar but a different colour. Still worked though.

Hope this helps,

Simon

MarekH · Post by **MarekH** » Sat Dec 19, 2015 3:46 pm

All that those little temperature control valves are going to do, assuming they will work, is make the flap in the airbox inlet open or close a little, depending on air temperature. This will have the great effect of mixing hot air from above the exhaust manifolds with colder air from the trumpets.

You can happily live without them and you will eliminate another potential source of vacuum leaks.

If you can get yourself the Haynes Stromberg carburettor book then you ought to be able to work out what the purpose of those castings is.

kind regards
Marek

vee12eman · Post by **vee12eman** » Sun Dec 20, 2015 5:57 am

Hi Marek,

I do have the Haynes Stromberg book, but I couldn't see what these items do, is it because my early UK car doesn't need them? I can't actually see what they connect to and I am always willing to learn, could you enlighten me?

As for the temperature compensators, I am well aware of their purpose and note that since fixing them properly, the choke can be pushed in much earlier with the car still running well. As such I am a big fan and very pleased to have them working properly reducing fuel consumption, but more importantly, reducing the raw fuel in the cylinders washing away lubricant on start up and cool running with choke out.

Regards,

Simon.

MarekH · Post by **MarekH** » Sun Dec 20, 2015 10:13 am

Dear Simon,

The original poster is talking about the temperature valves inside the airbox to mix hot and cold air, which aren't really needed. The temperature compensators on the side of the carburettors that you refer to are a totally different item.

If you look at the page 25.52 of the parts manual, then the implication is that the castings originally refer to simply connect to unfiltered manifold vacuum further upstream than the airbox. As such, I suspect they can be simply be left open and pick up filtered airbox vacuum, which will be close to the same value much of the time. I don't recall ever doing anything other than that when I was running carburettors and it never stopped the car from running. In essence, I suspect that this passageway sets the reference vacuum for how much fuel is drawn across the needle.

Given the above, the net effect will be probably to set the vacuum/petrol height slightly differently at partial vacuum and as such if you cross check which cars had this, I suspect you'll find that they also specify different needles - i.e. it'll be an emissions thing and cause the car to run slightly leaner or richer in a narrow band of the operating range. That's my guess, without looking at a manual.

kind regards
Marek

Michael Herlihy · Post by **Michael Herlihy** » Sun Dec 20, 2015 11:17 am

Thank you all for your prompt replies.
The car in question actually belongs to an elderly gentleman friend of mine who has had the car from new. As a relatively knowledgeable classic car enthusiast and mechanic I am trying to help him solve this dilemma. The car is a 1973 (L) convertible auto and as such has the fairly late engine type that is overloaded with emission equipment with its' plethora of cross engine pipework. We could of course modify the system and remove a lot of this but the fire only affected the O/S and he is quite keen on originality.
I agree that the temperature control valve in the airbox merely operates the hot/cold air flap and the manifold vacuum in fact holds the flap in the hot position so simply blanking off the vacuum pipe will disable the system. No big deal and nothing would be visible.
The two pairs of castings are bit more of a problem as they form part of the mounting system for the whole airbox assembly as well as performing a balance function.
If we look at the SC Carparts catalogue. V12 Srs 3 (1971 - 1974). Chapter 6 Carburettor and air filter. Zenith Stromberg 175CD carburettor and air filter. The parts in question are numbered 34, 35, 36, 37. As I mentioned, these have been destroyed by the heat. I could machine some spacer sleeves on my lathe to accept the mounting bolts and with appropriate blanking of various orifices/spigots I'm sure the engine will run just fine but of course won't match the N/S cylinder bank hence the original post.
Thanks again to all,
Mike

vee12eman · Post by **vee12eman** » Sun Dec 20, 2015 11:19 am

Hi Marek,
Yes I see the point now. As to the Temperature 'compensators', I actually meant the valves, which Michael, the OP referred to, marked AC. As I stated, these are available from Barratts and as you say, drive the valves to mix hot and cool air until temperature rises enough to close them and allow just cold air (therefore more mass air flow) into the carbs. The warm air aids atomisation and ignition while the engine warms up.

Michael.
Prior to replacing the temperature valves (the ones marked AC), check the flaps in the inlet trumpets actually respond to vacuum otherwise your money is wasted on them. Mine were ok except that the flaps fouled the walls and I had to adjust them accordingly. They commonly fail. In fact mine had stuck shut with painting but as Marek says the car will run just fine without them. However my car definitely runs better with them working in that I can come off the choke more quickly. I note that no-one has come forward with parts for your melted alloy castings. Again you can do without but blank off where the pipes enter the air filter boxes. At least this is true of my car which doesn't have them from the outset, with no holes in the air filter boxes for them. If you are still trying to find replacements try RMJ Smith.

Hopefully this has helped and hopefully in future you will post your results and some other details of your car.

Regards,

Simon

vee12eman · Post by **vee12eman** » Sun Dec 20, 2015 11:30 am

Hi Michael,
I was just posting as you did so we crossed over a little. You could fit earlier mounting bolts as fitted to the earliest cars like mine. This could be done both sides but will of course not be original. However, very hard to see and doesn't need spacers to be made. Still, try RMJ Smith on 01270 820885,

Regards,
Simon

MarekH · Post by **MarekH** » Sun Dec 20, 2015 12:10 pm

Since all they will do is provide a vacuum reference to somewhere, why not just get some plastic tubing, wedge it into the appropriate holes on the face of the stromberg plates, join with a Tpiece and link it up as it was before. You won't know unless you look inside the airbox that it isn't original and whatever functionality it had then, it still will have now.

I honestly wouldn't spend any money on it.

kind regards
Marek

PeterCrespin · Post by **PeterCrespin** » Sun Dec 20, 2015 1:34 pm

For functional symmetry, if there are two sets on one bank and none on the other, use one each side as part of a Marek-style workaround. I agree that as everything is invisible I wouldn't sweat it.

If on the other hand the old man is loaded and wants originality, even in unseen aspects, I'd spend time Googling and phoning for parts, rather than debating the whys and wherefores.

Michael Herlihy · Post by **Michael Herlihy** » Sun Dec 20, 2015 2:58 pm

Thanks to all.
I think unless we can find some lurking in a shed somewhere then we will follow the general trend of advice and rig something else.
Mike

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