carburetor question for experts

[deQuincey]

hi

i have one important question, i have been reading two different manuals of the zenith-inat carburetors overhauling, one seems to be an US version document, very detailed and nice, and the other is in french (so supposed to be european), it is not so clear, but the specification table is sharp !

i am speaking about this:

this is the number of washers to space the float-valve in the fuel reservoir,

according to the usa manual, in every 3 litre engine it should be 2mm, so 2 washers

but the french one says 1mm (1 washer) for all the engines (2,5, 2,8, or 3litres)

what can i do ? i own an euro spec. original 3.0 litre car, so: should i follow the french manual or the other one ?

which function will be affected by this decission ?

regards

 

[Stevehose]

The mm amount is determined by the float clearance "A", from the manual, so see what this works out to be, otherwise I would try one and see if it floods or starves then adjust:

This distance should be as follows:
INAT 35/40 19.0 ... 19.5 mm


If the measured distance is within this tolerance range, install a I mm thick sealing ring between float needle valve and bedplate.


If the actual distance is out of tolerance, correct by altering the sealing ring thickness. Before the measurement is taken, the float mounting must be in good working order.

 

[deQuincey]

thanks, this is the third version manual i have seen regarding this item, i know it seems to be the most scientifical one, but ...

which is the good one ?

 

[Stevehose]

I referred to all 3 when I did mine because neither one seemed complete, 61Porsche would know, perhaps PM him.

thanks, this is the third version manual i have seen regarding this item, i know it seems to be the most scientifical one, but ...

which is the good one ?

 

[61porsche]

Zenith float setting

DeQ,

Comment- your photos show staining around the valve which means that gasket was leaking. This was causing your rough running.

Do not use the aluminum washers. Use the red or grey( 2mm) fiber washer from the kit. As far as I know the only correct float valve gasket kit comes from Mercedes. ( They are all fiber- 1/2, 1, 1 1/2, and 2 mm.)

The manuals assume all new parts in perfect order. After 40 years, the float may weigh more, the pivot is worn a bit. Don't worry about it.

Once you have the carb all back together and running- you will know if the float is right.... visually you will see fuel coming out of the venturi - drips or lots of fuel. Only then, change the gasket with the carb body ON THE CAR.

When tightening this float valve- snug and a little more. They can and do break.

I have done all sorts of adjustments to the thickness- two washers( fiber only), brass shim on the float. What my experience tells me is that there is a small angle of float before it rubs on the bowl. So don't go too thick and start doing more. When this happens, and you pointed it out, is the gasket is slightly different and rubs the float thereby hanging it slightly open than
the gasket thickness. Trim the gasket around the fuel bowl if you must. The float must swing freely.

Today's gas is much different than when the cars were new. The specific gravity of the fuel effects the float which has a very specific weight.

Stop the drip.

Fix the leaking float valve. Read the manual on how to pinch off the hoses to check the valves BEFORE rebuilding or carefully study the parts for wear, staining, etc.

My hat is off to you my friend- hand made gaskets! I don't think I could even find the material any more.

P.S. Your choke- I have never seen one where the kickdown was held just with the spring. There is a serratted washer and thin nut on all I have seen.

P.S. P.S. The slotted screw in the choke housing looks to be leaking from the gasket behind the housing by the evidence of the crud around the screw head.

keep the pictures coming....bravo.

 

[deQuincey]

thanks and some debate

DeQ,

Comment- your photos show staining around the valve which means that gasket was leaking. This was causing your rough running.
probably, but take care, that was a fiber washer !
now i went to a carb repair shop and they gave me aluminium washers !

Do not use the aluminum washers.
WHY NOT ?, lets see: these are not washers only, they are spacers, but also they have to seal the fuel that came with the pressure given by the pump. so why not use aluminium, i am using aluminium washers in many other aplications inside the engine, i.e. for the oil pressure sensor, so why not ?

Use the red or grey( 2mm) fiber washer from the kit. As far as I know the only correct float valve gasket kit comes from Mercedes. ( They are all fiber- 1/2, 1, 1 1/2, and 2 mm.), any help about htis kit ? where to find ? if from mercedes, any reference ?

.

 

[deQuincey]

DeQ,

P.S. Your choke- I have never seen one where the kickdown was held just with the spring. There is a serratted washer and thin nut on all I have seen.

P.S. P.S. The slotted screw in the choke housing looks to be leaking from the gasket behind the housing by the evidence of the crud around the screw head.

can you post a pic of the common choke, and detail of the serrated washer ?

 

[61porsche]

1. My concern from your picture on the choke kickdown is that there is evidence of rubbing on the choke diaphram rod. Bend it slightly away. my mistake on the kick-down- nut on the shaft of the throttle butterfly.

2. Al. washer- never seen it used on the float valve. if you feel that the alloy is soft and can be tightened on cast alloy without cracking it. I agree that it's ok on cast iron- a lot denser material. Proceed with caution otherwise.
US kits from Walker or CA come with only two washers- one red 1mm and one grey 2mm. A nitrile rubber O ring of the proper thickness might be the more modern approach.

3. Mercedes sold just a washer kit with the 4 washers. I have only seen it on Ebay. The BMW later suppliment mentions them, but of course that was then and years ago.

I always just end up with the 2mm grey fiber.

If you carefully examine the float valves shown in your photos, there is a height difference between the ball type and pin type. Going past 2.5 mm and the float won't open enough to full open. ( I did this and had to correct it. Turned out to be the gasket not being tightened enough. Second condition is that the gasket for the section over hung the bowl section and held the float from opening very far.

Tip- when placing the float section on the body, hold the float closed with one finger.

 

[deQuincey]

1. My concern from your picture on the choke kickdown is that there is evidence of rubbing on the choke diaphram rod. Bend it slightly away. my mistake on the kick-down- nut on the shaft of the throttle butterfly.
yeah, i bent it back today, see the reparation thread

2. Al. washer- never seen it used on the float valve. if you feel that the alloy is soft and can be tightened on cast alloy without cracking it. I agree that it's ok on cast iron- a lot denser material. Proceed with caution otherwise.
US kits from Walker or CA come with only two washers- one red 1mm and one grey 2mm. A nitrile rubber O ring of the proper thickness might be the more modern approach.
my carbs, came originally with a copper washer, you might know i have also two sets of american carbs, also with copper washers,

today i called the people of the carb repair shop, and they say that all they knew was copper or aluminum washers, but you were right: special care on the tightening

3. Mercedes sold just a washer kit with the 4 washers. I have only seen it on Ebay. The BMW later suppliment mentions them, but of course that was then and years ago.

I always just end up with the 2mm grey fiber.

If you carefully examine the float valves shown in your photos, there is a height difference between the ball type and pin type. Going past 2.5 mm and the float won't open enough to full open. ( I did this and had to correct it. Turned out to be the gasket not being tightened enough. Second condition is that the gasket for the section over hung the bowl section and held the float from opening very far.


Tip- when placing the float section on the body, hold the float closed with one finger.
thanks

,

 

[deQuincey]

new question

take a look to this assembly:

is it alright ?

can you see the serrated part down there ?

can you discuss the position of the spring end in the left side of the pic ? is it ok there ?, should it be in the next member of the part ?

 

[61porsche]

Place the butterfly in the closed or normal position. The cam and screw should rest on the smaller step. Then I can tell.

When cold, and the accelerator is pushed, the spring action moves that cam and screw to the larger part. The throttle butterfly opens a little.

 

[deQuincey]

another question

regarding the positioning of the heater housing choke cover the manual says that you have to align the marks, but i find two marks:

in the following pic, red arrow shows the cover serrated mark (this one can be positioned by rotating the cover
the blue arrow shows a notch, a small mark
while the green arrow shows a greater mark
which is the one to be aligned ?
what does the rich sign mean ? is it any adjustment that can be done there by rotating towards the "rich" direction ? what action does affect this, the cold iddle ?

regards

 

[61porsche]

Turn the page in the manual. There are two settings. One for Euro and another for US.( runs leaner- more choke; second notch.)

For moderate weather use the Euro setting. The first notch.

The important part is that they are both the same ; carb to carb. You may well have to watch the choke flap operation to make sure both butterflys open relatively the same. ( Come off choke.)