We're bringin' back the Flat Tops!

[Zup]

7 hours ago, motorman7 said:

Interestingly, it looks like the original one was folded over as you can see in the last pic.

Indeed!

During the rebuild of my flattops I had the same issue.

From a NOS set of power valves I purchased, I found that on one valve there where two screws that completely missed the intended holes---one of the screws penetrated and wrinkled the diaphragm. It had to be incorrectly assembled from the factory!

No way it could function as intended. I replaced the diaphragm.

Might be a pattern here?

Wonderful work Rich, simply beautiful execution!

Edited January 25, 2019 by Zup

[Captain Obvious]

Nice work. Soon people will be clamoring all over each other to replace their round tops with flat tops.       OK, maybe not.

Do you really think that one diaphragm was folded over and pinched? I would expect a permanent hard crease if that were the case. Maybe it just shrank up a little and rolled under itself after you took the power valve apart. Doesn't really matter though as you're replacing both of them.

And I think I mentioned before... Don't throw out your old bowl seals. You may find they work better than the new ones from the rebuild kits.

[motorman7]

2 hours ago, Captain Obvious said:

Soon people will be clamoring all over each other to replace their round tops with flat tops.    

I think you are a prophet.  I think there will come a time when it will be popular for the '73 and '74 owners to put the flat tops on.  They just need to see more nice examples.

 

2 hours ago, Captain Obvious said:

Do you really think that one diaphragm was folded over and pinched? I would expect a permanent hard crease if that were the case. Maybe it just shrank up a little and rolled under itself after you took the power valve apart. Doesn't really matter though as you're replacing both of them.

And I think I mentioned before... Don't throw out your old bowl seals. You may find they work better than the new ones from the rebuild kits.

I am pretty sure it was folded under, but could be wrong.  I took it off very carefully.  The material is very supple, perhaps that is why no crease.  Plus, there was a bunch of black 'gunk' right in the area of the crease on the last aluminum section.  Not sure what the gunk was, but it came off easy with carb cleaner.  Will have to see if I have pictures of that.  Will also see how the pump in the second carb looks.

I  should be able to finish out the carbs this weekend...assuming I get my throttle shafts.  Will also carefully save the bowl seals.

[rcb280z]

Wow, nice work!

I wonder how much Nissan charged back in the day to rebuild the flat tops. Couldn't have been cheap but then again it's never cheap going to the dealer now is it? The flat tops look complicated.

Just curious.

Edited January 26, 2019 by rcb280z

[Captain Obvious]

I wouldn't be surprised if the dealers just pulled them off and replaced them with round tops as well. Sure would have saved a lot of time for their techs rather than having to understand and properly set-up the flat tops.

I wonder. Anyone here have any dealer experience from back when these cars were still going to the dealers for service? What was the internal Nissan reputation of the flat tops?

[motorman7]

2 hours ago, Captain Obvious said:

I wouldn't be surprised if the dealers just pulled them off and replaced them with round tops as well. Sure would have saved a lot of time for their techs rather than having to understand and properly set-up the flat tops.

I wonder. Anyone here have any dealer experience from back when these cars were still going to the dealers for service? What was the internal Nissan reputation of the flat tops?

I agree, there is definitely a steeper learning curve with these.  That being said, I really enjoy the challenge of re-building these.  It is nice to clean everything (love that Gumout spray) and re-assemble with fresh parts. 

 

Just got the throttle shafts in.  I like the coating and it is definitely durable as they use this stuff on racing pistons.  I did a quick test fit and they fit in nicely.  Not too loose, not too tight.  Not too worried about the color difference as most of this will be covered up...Pics are a little dark

Edited January 26, 2019 by motorman7

[w3wilkes]

4 hours ago, Captain Obvious said:

I wonder. Anyone here have any dealer experience from back when these cars were still going to the dealers for service? What was the internal Nissan reputation of the flat tops?

I have dealer experience from back in the day with my 73 240Z. Bought in July 1973 in SLC, UT. It was fine that summer. Over the winter I drove a bunch to both Denver and Albuquerque multiple times. Seems like the next summer is when I had my first vapor lock, more like a loss of power, like 25 to 30 percent, very noticeable but it still ran. I could always start it after being parked, but it would take some cranking. Took it in multiple times. They put on the fuel rail insulation, that didn't really help. They added the electric fuel pump, helped a little. On hot days on the way home from work I'd pop the hood latch like mentioned before. It would help some, always got me home. They fiddled with the flat tops a bunch, but never hinted that the carbs sould be swapped for round tops. It was pretty much like that the rest of the ~20 years I drove it. Other than the really hot days in July and August the flat tops were fine for over 100,000 miles.

Wilkes

[Captain Obvious]

9 hours ago, w3wilkes said:

They fiddled with the flat tops a bunch, but never hinted that the carbs sould be swapped for round tops. It was pretty much like that the rest of the ~20 years I drove it.

Thanks for the dealer experience. I have heard (read it on the internet) that sometimes dealers got fed up with return complaints and just pulled the flat tops off and threw a set of round tops on instead. Easier than teaching their techs how to really really deal with the flat tops.

 

[Captain Obvious]

11 hours ago, motorman7 said:

Just got the throttle shafts in.  I like the coating and it is definitely durable as they use this stuff on racing pistons.  I did a quick test fit and they fit in nicely.  Not too loose, not too tight.

Throttle shafts look cool. Make sure the butterfly plates fit in the slot and the retaining screws still fit the threads. I don't know how thick the coating is, or if it did a good job of getting into the nooks and crannies, but if there are any issues it would be easier to deal with before the shafts are back in the bodies.

[Zup]

Good stuff here!

Interested to know, what were the charges were for the dry film coating of the throttle shafts?

The EGR valve plating looks great! Did you have them plate the entire assembly or did you find a way to disassemble the diaphragm mounting portion from the cast iron base?

Have any of the plated items with internal cavities (tubing, housings, etc.) exhibited bleed out from the plating process that discolored or degraded the surface plate finish?

@Careless described this issue and his use of silicone and plugs to prevent it, as he had the plating done for a restoration he was doing.

[jonathanrussell]

@motorman7..... the yellow zinc plating looks fantastic. Color looks great and nice level of shine. Apologies if you have mentioned this earlier but can you please describe what you did to prep the parts before sending to Sav-On?

Thanks. Really enjoying this topic.

 

[jayhawk]

21 hours ago, Captain Obvious said:

I wouldn't be surprised if the dealers just pulled them off and replaced them with round tops as well. Sure would have saved a lot of time for their techs rather than having to understand and properly set-up the flat tops.

I wonder. Anyone here have any dealer experience from back when these cars were still going to the dealers for service? What was the internal Nissan reputation of the flat tops? 

I've read the same thing on the internet, but have never talked to anyone that actually happened to.  Probably because if true, (since the internet says so) there are very few folks still around that actually owned Flat Top cars during the warranty period of the '73s and '74s. 

In my case,  even though I had no problems, my dealer installed the V3 kit (electric fuel pump, fuel rail insulation. etc) at no charge.  I purchased the car in April '73 and the V3 kit was installed July of '74 at 11,022 miles,  immediately after I returned from a 8 month Navy deployment (the car was in storage from Nov '73 to July '74) So the issues with the carbs must have been cropping up early in '73 since Datsun started installing HMB46-2 in production in '73.  My car is a 10/72 production, so it had the -1 carbs until I foolishly installed round tops in 1980 at 117,000 miles.  

A little side note:  In August '74, my dealer hosted a Fun Run through the Cascades and Datsun sent a rep who gave a presentation on the new flat top carbs.  I do not recall details of his presentation, but do recall it was positive about the nice new features and advantages of the carbs.  So they were making a case for the carbs even to owners in cool climate western Washington.  (nobody I knew then with '73s or '74s had vaporization/percolation problems, but the climate likely had something to do with that)