The 'E' Type Forum

Hi on my series 3 the hot air pick up pipes are missing from the back of the air filter box, there is just a hole where they should be. What do they do and where should they be go. Should I notice any improvement to the running of the engine if I fitted them?

Hi,

The purpose of the hot air pick up pipes is to pick up warm air from around the manifold when the engine is cold. Their operation depends upon two temperature sensing air valves, fitted inside the filter boxes, which sense the inlet temperature. When cold, they open and vacuum pipes fitted between the inlet manifolds and the valves transfer vacuum to units fitted in the inlet tract of the air filter boxes.

These vacuum units act in a similar manner to the vacuum unit on a distributor, except in this case, they close off the intake from the front of the car and instead draw air through the hot air pipes which you say are missing in your case.

They do this because at cold temperatures, the inlet tract of the V12 with Strombergs is very inefficient and the fuel tends to vaporise on the manifold walls. Heating the air coming in helps vaporisation and should make the car smother running, more efficient and reduce the length of time the choke is out.

As to whether it makes much difference ? this is debatable. I have not had this system connected on my car since completion and when I tested the temperature sensing valves, they were not working well as they would not seal when closed. I am in fact currently awaiting new valves from SNG and will also need the new vacuum hose that goes with them to make the connections. My car runs just fine without the system, but then I live in Australia and I doubt I have ever tried to start and run the car at temperatures much below about ten Degrees C. However, I am hoping this will make the car more efficient at low temperatures as the engine and the huge volume of coolant take so long to warm up and allow the choke to be released.

It is no point even pursuing this if the vacuum operated valves in your air filter box inlets are not working, so test these first, sucking on them will operate them, but you may need to free them up and lubricate them first ? mine needed some minor adjustments as they were sticking inside the air boxes, a little judicious bending helped that. I don?t have a parts manual to hand but I can tell you the part numbers later if you need them.

All the best, I hope this helps.

Simon

Thanks that is very helpful, the car runs fine but can take a little while to warm up from cold. I will check the valves and see if they work. Do the hot air pick up pipes just hang down towards the exhaust manifold or are they routed somewhere else?

The exhaust manifolds should have tinware around them with a spigot for the other end of the short hose from the adjacent filter box. This tinware is important not just for supplying ducted hot air on startup, but also to somewhat shield the inlet system immediately above each manifold.

Sounds like your ducting is missing if you can't easily spot the attachment. Browse the engine photos on www.xkedata.com for similar cars and you're bound to see what you need.

Pete

Thanks I will check to see if the spigot is fitted. Thanks for the link it is very helpful, looking through the photos quite a few seem to be missing the hot air pick up pipe the same as on my car.

Dave