Carb Needles Used In Non-American Flat Tops

[Captain Obvious]

So here in the US, they used P/N 16354-N3310 needles in the flat top carbs in 73 and 74. The parts manuals says they used the same needle for both years. Then in America they changed out the carbs completely in favor of fuel injection in 75, but I know that's not the case in other parts of the world.

So I'm wondering if they used the same needles in flat top carbs in other parts of the world from 73 to 78. Did they use the 16354-N3310 globally, or did they use something else?

So do any of you non-US enthusiasts have any experience with this? Off the top of my head, just tagging people (not in the US) I can think of?

@kats @EuroDat  @dutchzcarguy  @Gav240z   @RIP260Z   @jonbill @Jason240z

And just because everyone likes pics, here's a pic of 78 flat tops that I hoovered up some time ago:

[Gav240z]

If I get a chance I can look in the Australian Market Parts Manual to see what part no's they quote for these.

[HS30-H]

7 hours ago, Captain Obvious said:

So I'm wondering if they used the same needles in flat top carbs in other parts of the world from 73 to 78. Did they use the 16354-N3310 globally, or did they use something else?

So do any of you non-US enthusiasts have any experience with this? Off the top of my head, just tagging people (not in the US) I can think of?

I'm not on your list, but this is something I've been asked to look into before.

The UK market documentation (FSM, R-Drive parts list & L26 Engine Service Manual) show that three variants of carburettor were used between August 1973 and 1978. They were the HMB46W-1A, 1B & 1C.

The R-Drive parts list shows all the component parts and part numbers for the preceding HJG46W type, but not for the HMB46W. And if you look in the L26 Engine Service Manual it warns strictly against dismantling the piston chamber, piston spring, piston weight, suction piston and  needles. They are very firm about it. I guess they didn't want mechanics to mess with them. Possibly because of emissions-related calibration worries?

There may well be a document which gives the part numbers for the needles, but I haven't seen it. Sorry.

 

[dutchzcarguy]

I (luckely) don't have any experience with the HMB46W carbs.. As i never had a car with those monsters.. (Many years ago i knew someone local that had a 260z and kept on complaining about these carbs because they were impossible to set to a good idle of 650-700 rpm's they were all over the place.

How do i keep e'm apart the good and the bad carb?  we say: "Hou Je Graag" to the HJG46W, what means: i like keeping this! The other one is: "Hou Maar Bij (je)" HMB46W, what means You just keep that (junk)  hahaha..  

Long... lóng time ago i bought 2 sets of HMB46W  complete carb sets for a few bucks just to investigate them .... still not took the time to do that hahaha... (the seller told me one set is working fine the other needs some adjusting.. oh well... i think they need both (a lot) of adjusting now! 

Think i got about 3 other HJG sets so 5 in total left somewhere on my garage attic..

About the partnumbers of the needles, i don't have any partnumber books.. 

[Captain Obvious]

Thanks all for the help so far. Hoping that someone can turn something up.

 

3 hours ago, HS30-H said:

The UK market documentation (FSM, R-Drive parts list & L26 Engine Service Manual) show that three variants of carburettor were used between August 1973 and 1978. They were the HMB46W-1A, 1B & 1C.

The documentation I have mentions nine different revisions of the flat tops (HMB46W-1 through -9) used in the US. But who knows how, or even if, those revisions correspond to your 1A through 1C. And beyond that, the doc I'm referring to is dated at the end of 1975, so who knows what happened after that through 1978?

Does your UK market docs indicate any time line as to WHEN those 1A, B, C variants were used?

[dutchzcarguy]

Here i got a page from a serv.manual of Nissan  It says on the back: Printed June 1986 !! so i guess one of the last ones!  Also "PublicationNo: SM8E-0L28G0 

 

I see they mention a HMB46W-1C and HMB46W-10 !

Sorry for bad picture but better than nothing 😉  I also got a serv. man from 1975 but no explanations in there for the carbs.. as they are in the engine books..

[HS30-H]

1 hour ago, Captain Obvious said:

Does your UK market docs indicate any time line as to WHEN those 1A, B, C variants were used?

The ones that I have to hand don't, no. But then I simply might not have the one document that does.

@dutchzcarguyhas just shown that the suffixes went up to '10' at least, but I have no idea when these supersessions were applied.

I think @RIP260Z is your man for this. Ian has done some good research on the HMBs which shows them to be a good design, unworthy of the 'boat anchor' reputation. Hopefully he will contribute. 

 

[Captain Obvious]

Thanks again for the help guys. I'll hold tight and hope others can chime in.

And I'm certainly in agreement with the flat tops being good carbs. Swimming upstream against strong current, but moving my arms anyway.

And thanks Dutch for that document page. I'll add that to my files. 

[dutchzcarguy]

19 hours ago, HS30-H said:

no idea when these supersessions were applied.

You would need someone with all the service bulletin's that Datsun/Nissan had in that timeslot.. but they are... like Hen's teeth.. i think/fear.. 😮 Maybe there is one somewere on line.. that would be nice! (I like to know if someone finds one!)

[Gav240z]

On 10/15/2022 at 12:12 PM, Captain Obvious said:

Thanks again for the help guys. I'll hold tight and hope others can chime in.

And I'm certainly in agreement with the flat tops being good carbs. Swimming upstream against strong current, but moving my arms anyway.

And thanks Dutch for that document page. I'll add that to my files. 

https://www.viczcar.com/forums/topic/5381-whats-the-difference-between-240z-carbys-and-260z-carbys/?do=findComment&comment=84116

https://www.viczcar.com/forums/topic/5381-whats-the-difference-between-240z-carbys-and-260z-carbys/?do=findComment&comment=116901
https://www.viczcar.com/forums/topic/9945-flat-top-carbs/?do=findComment&comment=116889

2 comments worth checking out. I've not had much first hand experience with the later flat top's but I have heard a few people know how to get them to run right and they work well when tuned correctly.

[Captain Obvious]

Thanks for the links Gav240Z.

[RIP260Z]

Sorry for the later reply, busy season with work.

I intended to restore an RS30Q, and had the car, but the CSP took its place, and the RS30Q was sold, so I never got to try I found/modfiy/stock set up.

It's been a while since I was in Flat top carb world. A quick look/thought.

On my parts microfiche, there is only two needles listed, 16354-N3500, N-86A and 16354-N3310 and listed as applied model is L26 Australia.

Mentioned above is HMB46W -1 to -10, looking in the 240z/260z fuel system modifications plus booklet, mentions on page 18 "note: HMB46W-5 and -9 carburetors have the improved choke valves (no stamped number)." On the previous page (17) is mentions F1 and R1 as the second type, the third type F2 and R2, where Fand R are front and rear carbs. This corresponds to choke part numbers, 1st type, no part number (and that page is missing from my microfiche), second type 16188-N3300 and third is 16188-N3310.

The power valves also correspond to F/R1 and F/R2, (16059-N3314 and 16059-N3313 respectively, with the later having a green blob of paint on the valve, which I have seen.

So, what I am trying to say, point to, is I think the -1 to-10 covers small modifications/tweeks, with the HMB46W's as there production progressed. It also on what model the carb was on. I am unsure if any JDM market had the HMB46W fitted (HS30-H?), apart from their recalled Fairlady Z with the 2.6L fitted. It could like the Hitachi HJG38-11, NOS I have, this having an -11 suffix. This carb was I think, ran as singles or twins on various models, the P510, Fairlady Z, B110, N10 Cherry, all these models. I very much doubt ran exactly the same carb, cc would mean that needle valve would differ. The fuel inlet pipe on the NOS one I have differs in orientation than others I have seen, does this warrant a -* number change? The HJ38 has its number etched on the side of the fuel bowl.

Which brings me back to needles...I haven't seen anything with 1A to 1C (probably as the 1st page of my copied microfiche is missing), but I think it is lining up with changes to other modifications/tweeks to the carbs. I did send a needle off to be matched with an SU Burlen one, and it was pretty close.

I completely stripped a pair of HMB46's years ago to try to get a better understanding of these "boat anchors" work. People can run these carbs successfully, and some can. It's only fuel air and vaccum...! The key I think is they have to set up just so, and are a little less forgiving than the HJG46W. Some of these set up points are in the fuel modification system. What I found on stripping them if I recall is the nozzle kit (16496-N3311) is very easily worn, where the needle cuts a groove/makes the nozzle oval, rather than a centred fit. I found the power valve assembles clogged up with carbon, the valves are made up of 3 or 4 plates, with the centre one has little set brass nozzles set into the aluminium housing. These power valves run off a separate curcuit if I recall, giving an extra shot of fuel at a certain level of throttle, so have to be clean. I think there is a knock on affect if things are just set up just so.

The throttle shafts like the HJG46 could do with bearings inserted like Z therapy do. Also, if I remember rightly, the HMB46W's there is only one idle mixture screw that does both carbs, linked to both via hoses. This makes tuning difficult, as there has to a happy medium (or unhappy) to get it to run as best it can. I did come up with a mod that gives you individual adjustment to each carb, which I think would help.

Fuel level, very crucial, they eye level glass is a faff to see. The volume of the fuel bowl, which is under the carb is quite small, so getting that fuel float set is crucial,which is linked to fuel pressure. I did think of a large fuel bowl (cut a slice off a spare carb and make it into a spacer) to give you more volume, but I never thought it all the way though and see if it would work.

I seem to remember a very small inset fuel filter in the carb body, another thing to keep clean. Also, there are devices on the air filter box that need to be kept in working order too.

Right cup of tea time. I hope that helps.

Cheers

Ian