Zenith V-type Carburettor, Jet sizes

[MartinRaine]

Hi Please dose any one know if a 5 or a 5 5 slow running jet is correct for a 1935 zenith carb and if you any other info on the jets, and settings. Thanks Martin

[george garside]

up to & including engine number 540469 slow running 5
after that 50

presumably thae chanage comes with the change to VM type carb.

[Keith Andrews]

Be awahere that the orginal british pool fuel was of a much lower octane and there fore of a far higher sperfic gravity than todays modern fuels...So going one step up (larger jet) would be a prudent move if cant check your O2 or COx levels.

Also If any play in the butterfly bushes will cause lean condition...It is basically a waste of time messing with jets etc if there is play in the butterfly bushes....ineffect a huge inlet manifold leak.
Check play in several directions....
Check vac leaks with a small pencil lpg torch ,only cost a couple bucks,(unlit) diected at different areas.

[george garside]

presumably this would apply more to the main jet than the slow running jet which provided a idle at around 200 rpm could be achieved would be deemed ok. I totally agree about the air leeks as no amount of rejetting will cure such a problem.

For what its worth , and just as a recount of what I di rather than A piece of 'technical advice ' I came up with the following low cost way of curing throttle spindle leeks.
If anybody decides to try it only attempt it on a scrap carb.
very carefully & slowly run a drill through the throttle spindle holes so as to return it to something like round - a round file can be used instead of drill - do not enlarge hole byond its largest worn diameter.The throttle shaft will now be a loose fit!. If possible check throttle shaft for lack of roundness at contact points and true up gently by wrapping with strip of emery paper & pulling back & forth.

Find or make to thin washers that are a good fit on throttle spindle ( but bit a oush fut).
File a little off the end of the boss on each side of the carb body through wich the throttle spindle passes, the amount filed off each boss being roughly equal to the thickness of one of the washers.

Remove choke tube

Gease throttle spindle ( vaseline ok) particularly in the bearing areas. Use a thin layer of grease i.e. so the surface of shaft is just greasy .

Assemble shaft & butterfly back onto carb making sure the butterfly is fully closed i.e. back throttole stop right off. Rig up sosme sot of device to ensure butterfly is jammed full closed as this will help to centrre the throtle spindle. I made up a piece of wooden dowel to go down the top as a tight fit.
Mix some original areldite ( not the fast setting stuff) or similer epoxy glue. Stuff areldite into gap between throttle shaft & hole in carb body until it comes out evenly on inside of carb . Glue the washers to the carb bosses . REmove sny surplus areldite from inside ventury before it sets! & leave carb in warm place for 48 hours.

All being well you should then have an airtite easy revolving throttle spindle on its new areldite bearing! I used this method on a number of worn carbs & always got a satisfactory result.

I did howwever experiment of one or two scrap carbs first & more or less any scapyard carb will do as long as it has a throttle spindle & butterfly so don't wast good or even bad Jowett carbs experimenting.
Usual disclaimer " if you get it wrong its your fault, not mine or the clubs" or words to that effect!

george

[Forumadmin]

or a carb restoration service can rebush for $15

[Tony Fearn]

( but bit a oush fut).george

George, you should have been born rather more to the North! I'm impressed with this dodge, but unless it's Gaelic I'm lost with this phrase!

Tony.

P.S. I don't think we'll ever come nearer than Llandridnod Wells to Anglesey, so are you coming?

[MartinRaine]

Hi i have a brand new carburettor that has never been fitted, so there is no wear on thes carb at all, i was just wondering what in a perfect world that slow running jet should be, Ps the engine is fully refurbished. Thanks Martin

[Keith Andrews]

presumably this would apply more to the main jet than the slow running jet which provided a idle at around 200 rpm

Yes but while out may as do it right get it better even on the idle circuit.

Goerge your drilling out etc, yes it will work IF drilled with a leader but very much a temp fix..
The correct method is remove the butterflt shaft, using a reemer with a leader so both shaft holes are perfectly lined up ..reem out and fix in new bushes...reem these to size with a leader and replace the butterfly shaft because it will be worn on one side.
Slide the butterflyy in, a drop of locktight on each screw thread, just nick up the screws enough for the butterfly to self center when fully closed...and put up to the sun or bright light getting it to center. Using a dolly crimp the lower side of the screws.

I have not done a single barrel carb..have done a 4 barrel Holley some yrs back....
My conclusion and what I have done since

or a carb restoration service can rebush for $15

Sums up very well
I would also be very hesident as to be using areldite...espec in our modern fuel enviroment and heat expansion co effirnt between the areldite and aluminum ally...IF anything I would be using an epoxy.
Got one question though Goerge, how do u stop the areldite/epoxy from gluing the shft to the body?

Once u have the butterflys re set DO NOT put heave springs on to hold your accerator pedal up or what ever....
This prematurly destroys so many carbs.
Look at most carbs , espec late model..they have a return sring built around the butterflt shaft...this removes any sidways loading and wear on the shaft and bushes...Yes have a secondary return spring..a light one. If the saccerator is too light under foot, also note car manufactures have a separtate spring mechanism for the pedal that doesnt load the butterfly shaft...for good reason.
If car manufactures thought they could save a few cents by using a heavy throttle spring on the carb they would have done so.

[george garside]

[quote="Tony Fearn"][quote="george garside"] ( but bit a oush fut).george[/quote]

George, you should have been born rather more to the North! I'm impressed with this dodge, but unless it's Gaelic I'm lost with this phrase!

Tony.

P.S. I don't think we'll ever come nearer than Llandridnod Wells to Anglesey, so are you coming?[/quote]

Sorry Tony I can't claim 'oush fut' to be Gaelic - merely failed attempt at touch typing. May manage a day at Llandidrod Wells depending on what other plans I have forced upon me !

george

[george garside]

[quote="Keith Andrews"][quote]presumably this would apply more to the main jet than the slow running jet which provided a idle at around 200 rpm [/quote]
Yes but while out may as do it right get it better even on the idle circuit.

Goerge your drilling out etc, yes it will work IF drilled with a leader but very much a temp fix..

Kieth - lasted fine for around 30,000 miles of daily use & was still fine when I sold the vehicle.

I would also be very hesident as to be using areldite...espec in our modern fuel enviroment and heat expansion co effirnt between the areldite and aluminum ally...IF anything I would be using an epoxy.
Got one question though Goerge, how do u stop the areldite/epoxy from gluing the shft to the body?

I thought araldite was an epoxy!

The aforementioned greasing of the throttle spindle prevented the shaft being glued to the body.

george



]

[Keith Andrews]

Kieth - lasted fine for around 30,000 miles of daily use & was still fine when I sold the vehicle.

To get to work for that ime ..and assuming its not wearing out actually checked no wear is very suprising...espec considering if was replaced with modern alloy bushes...Im not doubting you....99% of these fixes are simply patch repairs.
As too fine...can still be worn and not backfire due to lean condtion...Fine doesnt always = running ..espec when driving a car daily, one doent notice things going off ..one gets used to conditions slowly deteriate
Areldite and epoxy are different...check out the labels espec when appling to glueing different plastic types.
In general application epoxy is the more versitile.