Next Question
 

On the air cleaner, there is a winter/summer flap. I have spent the last hour researching its purpose and it is for icing up carbs I think, but my question is how it works.... mine is very loose and opens and closes easily.... is that the way it is supposed to be? I am concerned that when I am going down the road, it is going to close, limiting the amount of air to the carbs... is that possible and do people just basically block this flap open and leave it? In other words, how does it work? When is it supposed to be open and closed? 1970-71 240Z... Thanks

Pictures Please
 

Professor, any chance you can get some detailed pictures of it ? Looks like manuals for that year can't be downloaded at Xenon, so research is a bit harder. best to document this now, then in the future when I'm restoring my 240, I can refer to your fine work :)

Winter cold area option
 

Just doing some research, you probably already know it was a cold weather option, that not all Z's of those years had, I would say yours might be worn a bit allowing it to move freely, from what I could gather it has a switch on top, and should stay where set. So perhaps a little Mod to tighten the switch is all you need, or find a "non flapper" Air cleaner, I believe its the basic stock item, and would be period correct. Does yours have the duct from the exhaust manifold?

post from classiczcars
 

Mike B posted this, he had some very good info.

There was a Revised Edition Service Bulletin Vol 142 issued in Oct 1971 titled "Improvement of Emission Control System (1972 Year Models)". One of the revisions from the previous version of SB Vol 142 issued in June 1971 was the addition of a "Hot-Air Type Air Cleaner". It describes the manual summer/winter switch and the hose from the exhaust manifold to the air cleaner. There was also a separate Service Manual "Emission Control System for 1972 Year Models - Revised Edition" issued on Oct 20, 1971 that has similar information. This was also incorporated into the combined version of the 1972 Engine, Chassis and Body Service manual, but not the separate versions of the 1972 Service Manuals.

I don't see anything about the manual air cleaner temperature switch in the 1972 owners manual (at least the 3/72 edition), but the 1973 owners manual (3/73 edition) describes the operation of the Automatic Temperature Control Air Cleaner that was added that year.

-Mike

Sevice Bulletin Vol 142
 

This is for the 72, but should be close to yours

The Answer
 

Hey Mike... your research is better than mine and you found the answer I was looking for.... I now understand the thinking behind the flap, and yes, there is a duct from the exhaust manifold that enters between the flapper and the filter main body.... so when the flapper is closed, the engine heat exhaust is reintroduced into the carbs.... warmer air after a period of time than the outside air... There was a lot of discussion from the people who wrote in, that they lived in California and would not need this option. My car will not be driven in the winter here in Minnesota... so now that I have a little understanding, I am going to take a look at the spring loaded flapper and see if there is a way to lock it in the open position, from the manufacturer.... if not, I will find a way to keep it in the open position...... Thanks for your help and the supplements.... the one showing the exhaust duct is identical to what my air cleaner looks like... Dennis PS... The duct from the exhaust manifold to the air cleaner, is half gone....