Rear interior vents

[Richard McDonel]

Earlier this evening I posted a query about the vents on the rear quarter panels; specifically how does any interior air get to the exterior vents on Series 2  240s?  I found an informative discussion dating back to May 2011 that indicated there should be a set of holes, similar to those for the radio speakers, on each interior (plastic) quarter panel at about the same elevation as the exterior vent hole.  A couple of hours later. mulching through the cluttered outbuilding I euphemistically refer to as my workshop, I found one interior panel that I had dumped in with a pile of discarded parts (who says hoarding is a bad thing?), and yes it does have a block of small holes at vent height.  The replacements I bought from MSA and installed do not have these holes.  They are sold as being the correct part for all 70 - 73 240s, but  in reality they appear to be appropriate only for Series 1 cars with vents just below the hatch window.  

I can use my discard as a template and drill holes.  Just beware that if you have a Series 2, the parts on offer for all 240s won't work on your car.  

[cgsheen1]

The S30 chassis continued using the same side vents throughout the rest of the run (240, 260, 280).  If you're concerned only about originality of your internal panels you need the panel with the holes.  If you're only concerned about venting, any panel will do.  The Z interior is plenty porous - if not, why would they dispense with the perforations on the later years...  Interior air has many paths to the side vents.  

[Namerow]

23 hours ago, cgsheen1 said:

Interior air has many paths to the side vents.

Here are a couple of pix that I have on file that show the placement of the 'vent' holes in the later-design hatch side panels (I'm pretty sure that the panels for the Series 1 design did not have these holes).  I don't have a precise measurement (and I'm too lazy to go out to the garage to make one), but the holes appear to be about 2/3 the diameter of the holes used for the plastic rivets...

 

In the 1980's, I worked as a project engineer for a company that designed and built wind tunnels (not model-scale -- the real ones) for the automotive and aerospace industries.  We worked with Porsche, Honda, Volvo, Ford, Hyundai and others (even Williams GP Engineering, but that's another story).  It was clear that the auto manufacturers at that time were only just beginning to pay proper attention to locating and sizing the cabin extractor vents for effective HVAC performance.  The Z was designed in the late 1960's and the extractor vent positioning appears to have been based on educated guesswork rather than wind tunnel testing (although Nissan did own a wind tunnel at the time).  Even when working as designed, the Series 1's extractor vent system can be best described as an intriguing but complicated failure.  The re-location of the vents in the C-pillars got rid of the exhaust fume problem and the water drainage requirement (along with a lot of parts and assembly steps), but the revised design doesn't provide enough outlet area to be very effective.  So I wouldn't be too concerned about venting the plastic interior trim panels because it's not going to make much difference.

Edited December 9, 2018 by Namerow
Corrections made to text and pictures

[Richard McDonel]

Thanks gents,

Namerow - I'm shocked that anyone would think the design of a 240Z was less than perfect.

[Namerow]

Overall, I think it was a brilliant design... for its time.   Some of its shortcomings got remedied by Nissan relatively quickly (e.g. the angled halfshafts).  Others stayed pretty much untouched (you can make up your own list  ).  Of course, that's part of the reason why most of us enjoy owning these cars.

[Richard McDonel]

Thanks for your advice fellows.

In the end, I laid the new left-side panel on a sheet of plywood beneath the discard, and drilled matching holes.  As we all know, the plastic is pretty fragile, so I used a new drill bit and ran in at a slow speed.  Worked just great.  For the right side I drew a paper template, duct-taped it to the new piece, and again all went well.

 

[Namerow]

Any pictures for all of us 'visual learners'?