I was cleaning the dirt off the SU carbs from my 240Z (HLS30-01841 build date 2/70) as I begin the restoration process, and I noticed that the oil filler caps on top of the SU carb domes (where you add oil to the damping chamber) are metal and not the black plastic that every other 240Z I have seen has.

The tops of the metal caps are flat and smooth with no writing on them, unlike the plastic ones which have the phrase “tighten by hand” on them. The metal plating is about gone but you can tell they were finished with yellow dichromate.

The carbs are the original “4-screw” type and appear to be identical to any other 1970 carbs. I wonder if these caps are indeed original or were they part of some aftermarket re-build kit or maybe they are from another SU carb (even one of the British ones).

Anyone have any ideas?

I was under the impression that some of the very earliest 240Z carbs had metal damper caps. Not very many, but a first few. The low VIN of your car supports that. I suspect they are original.

IIRC, my 1600 Roadster had metal damper caps.

Shoot, you learn something new every day! I'm quessing but, based on my serial number (2126 3/70) they must have changed over to the plastic caps some time between Feb. 1970 and March 1970, as my cap are the black plastic units.

So I'm betting that these carbs with the metal damper caps have squared-off float covers, and no drain plugs in the float bowls. Am I right?

I should have done some more research. They are original! From the ZTherapy site http://www.ztherapy.com/ <http://www.ztherapy.com/>

So I'm betting that these carbs with the metal damper caps have squared-off float covers, and no drain plugs in the float bowls. Am I right?

No drain plugs, Arne, but what you mean by the "squared-off" float covers?

No drain plugs, Arne, but what you mean by the "squared-off" float covers?

The earliest float covers were round, with definite screw hole tabs. As shown here:

Later float covers were "squared-off" as shown on the bottom row here:

My 6/70 also has no drain valves and the squared off float bowl but, I do have the plastic dampers. The heat shield is also with out the notch.

I'm not certain what month car my carbs came from, but they are the same as yours, Jim, no drains, squared covers and plastic damper caps. Mine originally had the notched heat shield and flapper air box, though.

The parts car that I pick up this weekend is 4/71, and does have drains.

The earliest float covers were round, with definite screw hole tabs...

Later float covers were "squared-off" as shown on the bottom row here...

OK. I see. I have the round float covers. So, these are the very early vintage SU carbs!

That means I should restore them and sell my unused set of the later NOS "four-bolt" carbs that I bought from the dealer a few years ago!

If you're after originality, yes, the early ones should be restored and used.