2.7L CIS airbox cold start spider
 

I have seen two different air boxes for the 2.7L CIS.

One has no spider coming from the cold start injector and another has a metal spider. Are they interchangeable and do they require a different fitting between the air box and the cold start injector?

Thanks in advance!

The box with the spider is for the '76 or later engines with aux air regulators (no hand throttle).

If memory serves, the 77 came with the non-spider, but Porsche redesigned the boxes at some point to reduce backfires, so if you bought a replacement one after a certain date, it had the spider in it- don’t know what that date was.

Thanks for the replies. The engine is from a 1976 911S so I expect the metal spider is okay - cheers!

Well, my '77 (gray market, left factory in summer '76) didn't have the internal spider as best I recall. But it did have the hand throttle. Which turns out to be quite useful in the car's 3.0 CIS race car configuration depending on the weather and so on.

By '76 the S was the only model imported to the US. The silly non-S from '74 had been dropped from the model offerings, and the S designation wasn't needed any more.

You could probably get a borescope down in there to look - pull the connecting ribbed rubber boot, open the throttle, and put the scope in if you couldn't see what you need anyway? Of course, if you have a pop-off valve, just open it and look?

I believe the spider is a desirable feature - keep it. The airboxes (of the same port diameter) are interchangeable.

The air box that is currently on the motor does not have the spider (I had a backfire that blew the pop off valve apart and suspect air box damage). I have a line one a replacement that does have the metal spider and wondered if it needed a different fitting air box to cold start injector.

Thanks for the response - I agree. It makes sense when I look at it.

It's worthwhile to test the "new" box prior to installation (assuming you're buying used).

Locktite Plastic Welder epoxy is about the only readily-available adhesive that I've found that will stick to those to seal the seams. Don't try to take the box apart - just seal the seams.