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Air filter for '73

Dale B.

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I have an original '73 240z with 30k original miles. It is in excellent shape, no dash, cracks alloriginal hoses under hood etc.

I am in the middle of a tune up and had some questions about the air cleaner. My air cleaner has two holes, @ 1" in dia, in the curved end of the cover that look like something attatched to it at one time. What are these for? Also someone installed a K&N air filter but it appears too thick. The cover won't seat against the back plate when installed with this filter. I picked a replacement filter at my local shop and it too was too wide. is it possible that I have an air cleaner from a 260? the prod date on my car is 2/73. any ideas wouild be appreciated.

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Hi Dale:

Wow - 30K original miles, have you had it all along, or was it a great find on your part? A great find either way, I guess.

As for the air cleaners, the units are generally carb specific. Does your 73 have the roundtop or flattop carbs? If you have roundtops you most likely have the early air cleaner. If you have the flattops, you most likely have the later air cleaner.

The early and late air cleaner units are also visually dissimilar. The early units have round intakes (air horns) to the carbs, while the later units have square intakes.

As for the connections, on the early air cleaner the attachments consist of (1) the big (snorkel) air intake, (2) the carb vent tubes, (3) the valve cover vent tube, and (4) the tube from the air/smog pump. I think that's it, anyway.

For the later air cleaner the number of connections increased significantly due to the new emissions equipment. If it turns out you have the later unit, let me know, and I'll look up all of the connections in the '74 FSM.

Hope this helps,


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Hey! I lived in Woodland for 10 years! We moved over here a couple of years ago and I had been looking for a good Z since then.

I got this one just last week. IT runs very strong but I need to find out why it stumbles so much. Along that line I am trying to eliminate things systematically.. The Carbs are the Late model Hitachi's ( Flat top). I had a '73 while I lived in Woodland and I don't remember ever having this problem with the filter or the two large holes in the cover. These holes look like they came in the cover. No evidence of hacking.


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Hey -- small world out there! It sounds like Santa Rosa is the place to find z's, if your find is any indication.

Okay, so you most likely have the later air cleaner type. I would guess those holes are towards the very bottom of the cover, facing the engine? If so, (according to the FSM) they are part of a hot air system that activates while the car is warming up and allows warm air off of the exhaust manifold into the carbs until the temp hits 130degF or so and the valve shuts, only allowing air from the snorkel into the carbs.

The front hole is where the vacuum motor sits that opens/closes the valve. The other hole is the intake, connected to somewhere (I'm afraid I'm not sure exactly where) on the exhaust manifold via a piece of what looks like flexible heating duct material.

As far as air filters go, I'd guess that you picked up one that fits the earlier cleaner assembly. FWIW I have a K&N filter in my stock air cleaner in my '70 240, which fit, but not perfectly. My 260 is still a work in progress, so I haven't gotten around to picking up an air filter for it.

For the stumbling, it seems that a tune up is a great place to start. Most folks will recommend swapping in some of the earlier round top carbs for easier tuning and supposedly better performance. I'm rebuilding a set of flattops now for the 260 to see if they are really that bad.



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