OK, Colin ~ you had me pretty confused there before dinner, talking about all those bolt holes in your SUs.

I checked my Haynes manual to see what you were describing, then went to the garage and checked my own 1970 and some spare SUs I have. Here's the deal:

I was right originally. There are FOUR screws / bolts which hold the air filter baseplate to the front of the SUs. Yes, there are four "holes" in the front of each carb, but only two of them are threaded. The others don't get bolts.

My manual shows several types of airfilter baseplates. SOME (not all) of them have MOUNTING FLANGES on them, which fit into some of the unthreaded holes on the face of the SUs.

My car has individual filters on it now, so I had to dig out my spare baseplates to study them. One of the holes on the front of the SUs aligns with a blank space on the baseplate. Yes, the gasket has a hole cut into it for that hole. But there isn't a hole in the baseplate, so you couldn't put a bolt in there if you wanted to unless you drilled a new hole in the baseplate.

The gasket also has a hole cut into it for the other "threadless" hole in the SU, but that's where the manual shows the mounting flange. Neither of my spare baseplates ('70 and '71) has a flange ("factory delete") ~ so don't worry about that.

The only holes you need to fill are the two threaded holes, one on either side of the throttle throat. Two on each carb, total of four bolts.

The shorter bolt, with the combination head (wrench or Phillips), goes into the OUTER hole of each carb. The longer bolt with the extended head (wrench only) goes into the INNERMOST hole of each carb. Therefore, the extended bolts are closest to each other, and the shorter bolts are farthest from each other. (Short-long-long-short, from either direction).

The long butterfly thumbscrew bolts screw into the extended heads of the close-together bolts, holding the outside of the airfilter to the baseplate.

I have edited my original reply in your Post to reflect this info correctly.
Frank

*(PS ~ I also noted in your photo that you mounted your rear engine hoist loop onto the wrong manifold bolt. It goes on the rearmost exhaust bolt (sharing with the hot water tube flange), not the intake manifold. Exhaust manifold is made of heavier material than the lightweight intakes were ~ might make a difference if you ever actually try to lift the engine. Don't know if a Concours judge would take points for that or not).

And another thought, Colin ~

You might want to hold off mounting the outside of the 'breadbox' air cleaner until after you've started the car and tuned the SUs. The new carbs will need to be syncronized, which will require you to put a UniSyn over each of them to match the airflow. If you mount the outside of the air cleaner now, you'll just have to remove it again to do that, or to spray starting fluid down their little throats when you start it.

Hi Frank,

Thanks for all your careful research. I totally understand what you have described...and I checked and have all the correct hardware! Great!

I was only planning on putting the base of the air cleaner on so I could have all the vacuum lines going into it...but it won't really make a difference now that I think about it for tunning purposes. Also you are correct about the engine hoist bracket...funny thing is, that was where it was mounted when we got the car...and it seems like there isn't much length left on that last stud after putting on the heater line. I even put a slightly longer stud in there...I'll take a look at it tonight and see what works.

Thanks,

Colin

_________________
Currently Own - RED 70' 240Z, GREEN 72' 240Z

First Owned - New 72' GREEN 240Z
2nd Owned - Used BLUE 74' 260Z

just quickly...
when i sync my carbs i always keep the base plate on the carbs. the base plate usually has a kind of air trumpet on it to smooth the entrance of the air.
if you take the base plate off so its just the bare su it can give you a different reading. keeping the base plate on is more of a truer reading for when the carb/filter is reassembled.
i usually run my carbs without the filter and box. but i always keep the base plate on.. runs well but then becomes subject to sucking in exhaust heat.
remedy = run a heat shield..
just dont go driving down dusty roads:)