We're bringin' back the Flat Tops!

[RIP260Z]

Yes, fuel nozzles. Worn usually down to bent needles. Mine were also very carbonized (as were the power valves), all not helping them run well.

[Zup]

@Captain Obvious

 

1 hour ago, Captain Obvious said:

You're talking about the fuel nozzles:

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.    )

Good advice from our resident Sage---and I thank you again for the use of your "special tools".

I'm still up for a copy of them Bruce!

[motorman7]

3 hours ago, Zup said:

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.

Hi Jim, I am really excited about working on these, believe it or not.  Being a mechanical engineer by profession I really like all of the mechanisms, bushings, springs, etc.  I have been actuating and cycling some of the mechanisms prior to disassembly just to nail down each function.  I was actually pretty impressed with how smoothly the choke mechanism operated and how easy it was to remove the floats. Also, it was fairly clean inside, for the most part as you can see in the pics.

 It really helps to have the extra sets, that way I can be selective about the parts that I use for the primary set when the parts are re-zinced. I should have spares of most parts which will be nice.  Also, having a completed carb will make the re-assembly go a bit faster.  The key will be having everything organized and making sure all the parts operate well.

For the Choke vacuum breakers, I am hoping that there are two good ones out of the four.  I will hook up my vacuum pump and check them out here soon.

[motorman7]

1 hour ago, Captain Obvious said:

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!

 

Thanks for the heads up on this.  Will make sure I keep the parts well organized so I don't inadvertently swap these items. 

[motorman7]

3 hours ago, RIP260Z said:

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..

 

 

I noted the throttle spindle seemed a bit loose in it's bushings.  I will have to look into getting a new set of these.  I may also be interested in the diaphragms if these to not hold a vacuum.  Thanks for the comments. 

[RIP260Z]

Zup, motorman7, I looked into my notes (old receipt) [over 10 years ago] at what jet needles I got as a SU replacement. But, I don't think it is quite as straightforward, as the North American market got a different part number (16354-N3310) than the UK/Europe market (16354-N3500). The Australian market have the same as the North American market.

You quote N61, meaning what is etched onto the jet needle (yes?), whilst the microfiche for the European has N-56A. And my notes say N57 from the jet needle I physically took out. So, I had;

https://burlen.co.uk/

profile my jet needle N57, and got AUD1550 needle (KQ) as the nearest profile. If my memory serves me, it was very close, only at the point of the needle did the measurements differ, but this matters less, as this is where the full throttle operates on the jet needle. So, I would suggest getting yours matched, I don't know who in the US is any good on this, but I am sure someone else could recommend. If not, send them to Burlen...

Motorman7, if my memory serves me, there isn't a bush for the throttle spindle, just a drilled hole in the aluminium carb body. It maybe a solution if having bushings/bearing put in like Ztherapy does for the Hitatchi SU for the earlier models.

Here is also a picture of a pair of NOS nozzles for reference.

[Captain Obvious]

Love the pic of the NOS nozzle.

[motorman7]

56 minutes ago, Captain Obvious said:

Love the pic of the NOS nozzle.

Yes, same here.

Will post pics later today of forward carb disassembly.  

 

  Just had to share this quickly:

I usually talk with my wife about how the car work is coming along and what I am working on.  I came in from the garage yesterday afternoon and she asked me how my "Flat Bread Carbs" were coming along.  So, here is a nice picture of some 'Flat Bread Carbs'.......almost as nice as a good set of 'flat top carbs'.  ?

 

 

[jayhawk]

Love the Flat Bread Carbs!  With regard to Flat Top Carbs, I recently found this write up about SU HIF (IF= Integrated Float) type carbs (which is what our Flat tops are) and how they differ from the SU -HS types (round tops).  This is from a specialist in british SU carbs, specifically those on Austin A-series engines in classic Minis and similar cars.   This article is titled "SU Carbs - HIF, a more finely honed instrument"  and shows the purpose and advantages of the HIF design.  It is informative to note that there are a number of significant advantages to the British HIF design and only one disadvantage.  Anyway, I thought the folks following this thread might be interested.

https://www.calverst.com/technical-info/su-carbs-hif-a-more-finely-honed-instrument/

 

[Snekers]

Been following this for a while, I love seeing flat tops getting some love.

Not to derail the thread, but I’m currently rebuilding a set of flat tops, and I’ve run into a prediciment. I can’t seem to figure out how to take out the float pin, what’s the procedure? Thanks

[Captain Obvious]

3 hours ago, Snekers said:

I’m currently rebuilding a set of flat tops, and I’ve run into a prediciment. I can’t seem to figure out how to take out the float pin, what’s the procedure?

I'm not sure what you're asking here... If you're asking simply how you are supposed to remove the float pin, then you unscrew the cap covering the end of the pin, grab the pin lightly with a pair of needle nose pliers, and slide the pin out of the carb body.

If you're asking "I got the cap off the carb body and can SEE the end tip of the float pin, but it's stuck and won't come out. What do I do?" - Then the answer may be found in this recent thread where we were discussing just such an event:
https://www.classiczcars.com/forums/topic/60828-so-were-doing-a-73-restoration-project/?page=2&tab=comments#comment-560533

 

[Captain Obvious]

10 hours ago, motorman7 said:

she asked me how my "Flat Bread Carbs" were coming along.  So, here is a nice picture of some 'Flat Bread Carbs'

Nice!!         Haha!!