We're bringin' back the Flat Tops!

[motorman7]

3 hours ago, Snekers said:

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

Hi Snekers,

    The float pin can be removed by taking off the nut shown in the first picture below.  I put an arrow on it. On the rear carb, the pin came out easy.  The pin on the front carb was stuck,  so I soaked it in Kroil for a day (which didn't help)  and then ended up heating the housing lightly with a torch.  That did the trick and the pin came out.  Was very cautious with this as I did not want to damage the floats.  The forward carb also was not as clean as the rear.  In fact there was some blue-green colored goo in the area where the nozzle is.  The second set of carbs is very different as you can see and has the floats on the base plate.  I do not care for this design as much, but did want the zinc platable parts off of it.   Also, the sight glass cover is a different shape.  Interesting seeing the differences.  Nice improvements on the -2 carbs.

Both styles of the flat tops have bushings on the throttle spindle.  As you can see in the pic, the bushing looks a bit oval (worn) so will need to look into getting a new one of these.  Interesting seeing the green zinc chromate paint over the brass spindle rod.  Not sure why they did that, corrosion preventative?

The key to the re-build here will be all of those little parts.  I made sure to collect every item from both sets.  Will not send those to the plater as they may not make it back.  

I did a quick clean and polish of one of the vacuum chambers.  They clean up well.

[Captain Obvious]

11 minutes ago, motorman7 said:

I do not care for this design as much, but did want the zinc platable parts off of it.   Also, the sight glass cover is a different shape.  Interesting seeing the differences.  Nice improvements on the -2 carbs.

Agreed. The -2 carbs are certainly better. I don't think they ever got the bugs worked out of the -1 and just bailed. It's hard to come up with a post-mortem engineering analysis as to what happened with the progression from -1 to -2, but if I had to guess it was something like "Ooops! We better change that, and quick!"

Couple other comments. First, don't throw away your old float bowl seals. The new ones have a tendency to swell significantly when they come in contact with gasoline (stupid, right?), and you may find yourself wanting to resort back to the old ones and a smear of fuel resistant sealer. So try to carefully pick the old ones out of the grooves without tearing them.

Also, don't give up on the throttle shaft bushings just yet... Just because the hole is off center doesn't necessarily mean that it is oval worn. In fact, the bushing in your pic clearly has more steel on one side than the other, but I suspect they were pressed into the body and then line bored and reamed as a final step to assure alignment between the two bushings. And because of that, they may have ended being machined in such a way that the center hole is not concentric with the outside of the bushing. That doesn't matter... All that matters is that the two of them are in alignment with eachother and are in the center of the carb throat.

I would expect that even if something is worn some, the steel shaft would wear a whole lot faster than the steel bushing. So if you stick a 10mm rod into the bushing, is it all sloppy like, or is it still a good fit?

And about that green coating? I suspect it's a lubricant. So they don't have the sticky brass of the shaft riding on the steel bushing. I wasn't there when they designed it, but I suspect it's meant to be slippy. (That's a mechanical engineering term, isn't it?)

And last... Too bad about the broken alignment cone on the suction piston cover below. Is that a test piece just for clean-up and polish, or is that one that you were going to use on the final product?

15 minutes ago, motorman7 said:

 

[motorman7]

Aaahhh, I see what you are saying about the cones.  Yes, these are the two I plan on using.  On the one carb, both of the plastic alignment nubs are on the base.  On the other carb, one cone is stuck inthe vacuum chamber.

EDIT: sorry about the bad pics.  the vac chamber flange is hiding the base area where the cone is displaced.

Thanks for the feedback on the shaft.  I will clean both parts (shaft and bushings) up a bit and see how the fit is.  I will have to try and find out what the green coating is, and yes, it does feel 'slippy'.  It would be good if I could re-coat the area where the shaft contacts the bushing with the same green material or something similar.

Edited December 17, 2018 by motorman7

[motorman7]

Here's a better pic

[Captain Obvious]

Well to be clear... Your alignment nub has cracked in half and only HALF the nub is stuck in the chamber cover.     The other half is usually still stuck in the carb body, but in your case, it has fallen out somewhere along the way and years. Unfortunate, but not insurmountable.

Those two cones provide very accurate alignment of the chamber cover with respect to the center bore where the piston slides up and down and where the needle slides into the nozzle. If that cover is out of alignment, the needle will rub the side of the nozzle hole and wear something (needle, nozzle, or both). You can usually get it aligned relatively well just by feel, especially since you still have one good nubbin. But if you were insane and had too much time on your hands, you would make an alignment tool that would be used to fixture everything in proper alignment and use some epoxy to cast a new alignment nub to replace the broken one. A feat I have not yet needed to resort to.

And that green coating? I don't know what it is, but it was commonly used. I last saw that on a late nineties Sentra throttle shaft. At least it looked like the same stuff. Last time I was messing around with the throttle shafts, I took a different route and did this:

 

[Snekers]

5 minutes ago, motorman7 said:

Hi Snekers,

    The float pin can be removed by taking off the nut shown in the first picture below.  I put an arrow on it. On the rear carb, the pin came out easy.  The pin on the front carb was stuck,  so I soaked it in Kroil for a day (which didn't help)  and then ended up heating the housing lightly with a torch.  That did the trick and the pin came out.  Was very cautious with this as I did not want to damage the floats.  The forward carb also was not as clean as the rear.  In fact there was some blue-green colored goo in the area where the nozzle is.  The second set of carbs is very different as you can see and has the floats on the base plate.  I do not care for this design as much, but did want the zinc platable parts off of it.   Also, the sight glass cover is a different shape.  Interesting seeing the differences.  Nice improvements on the -2 carbs.

Both styles of the flat tops have bushings on the throttle spindle.  As you can see in the pic, the bushing looks a bit oval (worn) so will need to look into getting a new one of these.  Interesting seeing the green zinc chromate paint over the brass spindle rod.  Not sure why they did that, corrosion preventative?

The key to the re-build here will be all of those little parts.  I made sure to collect every item from both sets.  Will not send those to the plater as they may not make it back.  

I did a quick clean and polish of one of the vacuum chambers.  They clean up well.

 

12 minutes ago, Captain Obvious said:

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

 

Thank you guys for the help, mine seem like they’ll take some coaxing to get out. 

[motorman7]

Very cool, O-ring seals. I love it. For these carbs I am currently thinking that I will try and replicate the green material.

For the needle alignment, I would think the one nub and three screws would get me pretty close...but probably not perfect, Depending on the screw and tab hole tolerance. Interesting that the bottom part of the one nub is missing.

Sent from my C6902 using Classic Zcar Club mobile

[RIP260Z]

very nice, regards o-ring seal. Sorry if I mis-lead regards throttle bushing not been there, its been a while since I looked.... keep up the good work.

[Captain Obvious]

10 hours ago, motorman7 said:

For the needle alignment, I would think the one nub and three screws would get me pretty close...but probably not perfect, Depending on the screw and tab hole tolerance.

Agreed. (Without the suction piston installed) Put the cover on and put the three screws in but leave them loose enough that the cover can still rotate around the one existing cone nub. See how much play there is. Might be such that with the tolerance of the mounting screws combined with the single nub there might be very little play to worry about.

But if you do get energetic... I think all you would need is a steel rod with one end turned to be a precision fit into the hole through the suction piston cover, and the other end turned to be a precision fit into the carb body where the nozzle is installed. Remove the nozzle and then slip the rod into place and then put the chamnber cover on. The precision rod will align all the holes on the same centerline. Put the three screws loosely into place and then use a small syringe to inject epoxy into the alignment nub cavity to cast a new pin in place.

I wasn't there at the factory, but I've got a high degree of confidence they did something like that at the factory. You can even see the bubbles in the epoxy material in some of the pins where they didn't get all the air out. That looks like what happened to the intact pin on this body. Looks like a big air inclusion in the epoxy cone:

And I wish I could point you in the right direction for that green coating. I've never looked into it. But with as common as it is, I'm sure there's info out there to be dug up.

[Mark Maras]

 Googled "throttleshafts,greencoating". The green coating appears to be Teflon. Here is one business that coat throttle shafts, Orion Industries, orioncoat.com. There are probably more.

[motorman7]

53 minutes ago, Mark Maras said:

 Googled "throttleshafts,greencoating". The green coating appears to be Teflon. Here is one business that coat throttle shafts, Orion Industries, orioncoat.com. There are probably more.

Thanks for the lead.   This also looks promising and they are right down the road. 

http://www.olycoatings.com/dryfilm.html

http://www.olycoatings.com/thermo.html

I sent them an e-mail to get some more info.

[motorman7]

Got a 260 intake manifold off of eBay in today.  It has several common parts that I am missing and seems to be in nice shape. Paint will need to be removed.