Air / oil box advise

[trebor]

I got my hands on this air box but unsure whats going on with flexi pipe take offs. 2 small on the top 2 larger on the bottom half. There is also a plastic diaphragm box which looks as though its missing parts. If I suck :shock: on the small tube nothing happens so I assume the diaphragm is bust but the plunger in the middle goes down if you push it and you can feel a spring inside :? How does this control the heated air to the carb ? Or does it let more air in if required through the diaphragm controlled bit ?

 

[subheatadey]

It looks like you are missing the flap on the diaphragm that controls the air flow on the plus side you have the reducer for the oil breather. On top of the box there are two pipes which are part of the vacuum thermostat, one pipe goes to vacuum either on the carb or the take of on the manifold and the other pipe goes to the sprung loaded flap, it allows air to be drawn from the warm air from exhaust and then closes once the thermostat reaches the required temperature not sure what the temperature is I have heard 65 degrees. Those I believe are the best type a type 3 I believe but i am invariably wrong!

 

[trebor]

Cheers, it looks like I'll need another stat as there is a bit broken off. Thought I'd got a bargain

 

[trebor]

I've been looking around and not found any replacement yet, what should I do ? The part no is 113 129 802. I know I could just go back to normal filter but it would be nice to keep it as it was supposed to be.

 

[subheatadey]

There must be plenty about, I had the mark two oil bath before the one with the wax thermostat but be buggered i couldn't find the spring to operate it. I would run the oil bath as isjust block of the hole on the tin above the exhaust for now as it not going to be cold for months and run with it until you find the other bits or another one.

 

[trebor]

Trying to get my head round how it works, it looks like the weighted flap opens on demand and controlled only by a weight or suction. The stat flap opens to let air from engine compartment into the mix but nothing controls the heated air incoming. :? Suppose the engine stat and flaps regulate the heat :? :? oh sod it :lol:

 

[subheatadey]

The weighted flap is just that it opens on demand from suction of the engine maybe something to do with emissions but works well, but has no connection to the rest of it, totally different to the early wax thermostat on which was just a counterweight for the spring. There are two types of these filters according to the Bentley manual top of page 27 it says Quote - the thermostatic vacuum valve installed after December 1972 is different from that introduced on early 1972 models. It can be identified by a brass hose connection for the vacuum unit. On the early valve, both connections are black plastic. The later valve keeps the the flap closed to cool air regardless of engine load during the warm-up period. The early valve allows the flap to admit cool air under heavy load.

'Here endeth the lesson according to the bible Bentley - Amen'. :lol:

I must say though that having run without a non-operating filter for months and fitting the now operating air box it is running smoother - for some reason? So worth sorting out, next thing now is to look for some controls flaps for the dog house before winter.

 

[trebor]

I'll have to invest in a Bentley manuel.