We're bringin' back the Flat Tops!

[motorman7]

Got the Rotors and drums turned at the machine shop.  Cleaned and re-packed hub bearings.  Assembled passenger side hub and rotor to strut. Also attached the small brake lines.  Started disassembly of the intake manifold parts and horn.  Took lots of pics of these items for later reference.  

[motorman7]

Just got the clock in from Ron at  zclocks.com.  This baby looks brand new! New quartz mechanism has been installed.  Should be a lot more reliable than the old mech.

[motorman7]

                  I cleaned the outside of the rear drums and painted them with high temp ceramic aluminum paint.  They look pretty, but I am not sure that I like the finish.  They seem a bit too glossy.  I may change my mind and bead blast them and give them a high temp matte clear coat.

 

      And now what you all have been waiting for....I am venturing into the Flat Tops.  I have three sets of the flat top carbs with two of them being mostly complete.  The third set is missing the little diaphragm canisters, heat shields and linkage.  The set on the left has the '2' stamped on the body and I am assuming those are the original carbs.  They were also in the best condition.  My plan here is to disassemble the best two sets and get all of the yellow zinc parts out to plating.  I will keep the third, incomplete set, as a reference for when it's time to put everything back together. 

    I  have 4 rebuild kits.  I will look through those when I start to put everything back together.  Hopefully they are not too old and the rubber is all in good condition.

    I disassembled the rear carb and it looked to be in pretty nice shape.  The trick with getting the phillips head screws out is to put the screwdriver in the screw head and tap the top of the screwdriver firmly with a hammer.  That seems to loosen the screw and set the screwdriver deep in the head.  All of the screw came out nicely using this method.  I took lots of pics during disassembly to make sure this all goes back together correctly.  Pics are below.

    

 

Edited December 14, 2018 by motorman7

[Gav240z]

4 hours ago, motorman7 said:

I cleaned the outside of the rear drums and painted them with high temp ceramic aluminum paint.  They look pretty, but I am not sure that I like the finish.  They seem a bit too glossy.  I may change my mind and bead blast them and give them a high temp matte clear coat.

How about vapour blast, given they are made of alloy? Leaves a nice shot peened like finish and seals the surface to some extent against contamination plus it won't rub off like paint?

It's what I used on my SU Carbs.

[Zup]

Quote

The third set is missing the little diaphragm canisters

Choke vacuum breakers

If the goal is to make the choke circuit functional, those diaphragms are often damaged and will not hold a vacuum--you should check them soon using a hand vacuum pump and start looking for replacements that will hold vacuum.

It took me several sets to acquire one set of good diaphragms. Another fitzy spot is the linkage on the side of each of the carbs that actuates the choke vacuum breaker---a small u-shaped bent rod that connects the vacuum breakers to the choke plate shaft that is held by small cotter pins and has very small washers and springs as part of the assembly.

Most flat tops are missing these parts as previous owners and/ or mechanics defeated the choke circuit entirely by removing them from the carbs. There are specific adjustments that must be made to enable the choke circuit to function correctly and it is a bit of a pain to get set.

1973 Flat Top Carb Info from TSB.pdf 

or better yet

1973 240z 1974 260z fuel system modifications.pdf

Once set on a well maintained engine the choke circuit shouldn't need much more attention mechanically. 

You were familiar with the flat tops already from your previously owned 73 240Z, but these publications will provide some additional critical knowledge as to their adjustment.

[grannyknot]

7 hours ago, motorman7 said:

And now what you all have been waiting for....I am venturing into the Flat Tops.

Yes!  Never had a chance to see how a flat top is put together, kind of a rare sight as most were pitched years ago.

[Zup]

For me it is the sheer number of springs, washers, metal bits and small pieces that proves to be so daunting as compared to the SIMPLE earlier SU's. It is no wonder to me why they have been given such a dower reputation over the years.

Most of us , including me, are inherently somewhat lazy when it comes to complex assemblies---we just want it to work and be spared of the anguish of learning something new to make that happen.

[RIP260Z]

Are you going to rebush the throttle spindle in the carb housing? A big source of air leak, meaning no balance due to being worn.

the brass nut (you have pictured, from underside of carb) will come out that holds the needle guide in (its glued) as the needle can wear a groove in this guide, again meaning un-able to get the carb set. The needle is easily damaged/bent. They do come out, I have never found NOS replacements, but found an SU needle with the same profile.

I have some NOS diaphrams....somewhere..

Now this thread is getting interesting...

 

 

[Zup]

@RIP260Z

On ‎12‎/‎14‎/‎2018 at 7:33 AM, RIP260Z said:

I have never found NOS replacements, but found an SU needle with the same profile.

Please elaborate---what did you find as a suitable replacement for the N62??

Edited December 24, 2018 by Zup
corrected needle number

[RIP260Z]

It was many years ago...I sent a needle out of a carb to a SU (Skinner Union) specialist, and got them to match the profile of mine, with something SU already stocked. I will have to see what I did with the info..they did send me a pair of SU needles, if I recall.

[Captain Obvious]

Nice work on the flat tops. I'm sure you already know this, but just in case... Make sure whatever cleaning method you employ on the carb bodies does not destroy the original epoxy alignment cone nubbins for the suction piston cover (the "flat" in flat-top).

And make sure you keep each carb body, suction piston, and piston cover (the "flat" in flat-top) together as a matched set. They are aligned together using those formed in place epoxy cones and need to be kept together as a trio. And hopefully they haven't been mixed and matched in the past!

 

[Captain Obvious]

You're talking about the fuel nozzles:

1 hour ago, RIP260Z said:

the brass nut (you have pictured, from underside of carb) will come out that holds the needle guide in (its glued) as the needle can wear a groove in this guide,

I would not take those out unless there is an indicated reason to do so. Inspect in place... Make sure they are in good shape (not worn or corroded). Make sure they are at the proper depth setting and haven't been messed with in the past.

If they are in good shape and are at the proper mixture setting, then I would leave them installed. I wouldn't pull them just to pull them.

(However.... If you do decide you need to remove them, let me know as I've got some special tools that makes it easy-peasy.    )