the ACTUAL float height for the 1.7 340 with a solex carb?

[seannaayy]

hi guyss, gettin a bit miffed with the 340 as i cant quite get the float height set correctly, 1t i set it too low, so it bogged down on acceleration and around right hand bends, and now its too high so it pulls away nicely, but then looses power in midrange.

ive looked everywhere for the correct height to set it, and seem to be coming up with 33.8mm but cant see that being true as the float itseelf is more like 35mm :s this is the carb that has 2 sides to the float bowwl

has anyone got the correct method and sizes to set it? cheers *

*its very possible that im being stupid and keep doing it wrong or measuring it for and to the wrong places

[morgan105]

My books also show 33.8 from gasket to float with carb inverted.

[seannaayy]

am i being daft, is it for my carb or maybe a different one?

[jtbo]

hi guyss, gettin a bit miffed with the 340 as i cant quite get the float height set correctly, 1t i set it too low, so it bogged down on acceleration and around right hand bends, and now its too high so it pulls away nicely, but then looses power in midrange.

ive looked everywhere for the correct height to set it, and seem to be coming up with 33.8mm but cant see that being true as the float itseelf is more like 35mm :s this is the carb that has 2 sides to the float bowwl

has anyone got the correct method and sizes to set it? cheers *

*its very possible that im being stupid and keep doing it wrong or measuring it for and to the wrong places

Measuring is bit funny in those Solex carbs, you need to measure it so that that ball is not pushed in, but so that ball is touching float arm.

Haynes carburetor book instructs to measure from upper face of plastic float to gasket, but picture shows measurement being made from lower face of plastic float.

I can't remember how I did measure, but after a while tinkering I managed to measure it correctly from mine, but I think that picture was misleading, float is indeed larger than measurement value.

Also check vent valve adjustment while you are at it, that should have clearance of 0.5mm so that you can blow trough vent valve, but even small movement of throttle should close the valve, that might have some effect to flow of fuel too, those carbs can be quite sensitive and I think that is one thing hardly ever adjusted.

[morgan105]

You need to flip over the carb upper body so the float is at the top, make sure the needle valve IS pressed in and measure from the upper body gasket to the bottom of the float (which is now at the top when holding upper body upside down). Adjust as necessary by bending the inner float tag. There should be no more of a difference of 1mm on the floats.

[jtbo]

You need to flip over the carb upper body so the float is at the top, make sure the needle valve IS pressed in and measure from the upper body gasket to the bottom of the float (which is now at the top when holding upper body upside down). Adjust as necessary by bending the inner float tag. There should be no more of a difference of 1mm on the floats.

Doing it that way would mean that float need to be shaved off by around 2mm as float is higher than 33.8mm.

[seannaayy]

yeah this is the problem, think the vent valve is ok, however the gap is more than 0.5mm but does close instantly with a bit of throttle.
hmm is it definately done with the carb upper body flipped? and not when its hanging down? btw i have been trying with the upper carb body flipped, just a new idea heh

the measurement isnt taken from one of the moulding lines is it? is it definately the top(technically bottom) of the float?

thanks for the replies guys

[morgan105]

Bottom of float.

[jtbo]

Bottom of float.

Measure A is a lot more than 33.8mm as that black float is much more than 33.8mm.

[seannaayy]

yeah thats what im troubled about, what should the measure b, be?

and that diagram also shows the needle ball pressed in?

my god this is awkward haha

[morgan105]

What is the model number of the carb to make sure it confirms to what my books say?

[jtbo]

yeah thats what im troubled about, what should the measure b, be?

and that diagram also shows the needle ball pressed in?

my god this is awkward haha

I think that I recall what I found out when I had this issue, floats increase in size with time, there is no other possibility as I have two set of floats from very same carb and other ones were 3mm taller, that black plastic was much larger with other set of floats. They did look the same, but were not same size when measured.

What is then correct dimension of floats? If our floats are allergic to modern petrol and swallow like thumb you hit with sledgehammer, then that must be bit of an problem when trying to set cars so that they run properly?

Carb models Solex Sisac Z10/Z11 should be almost the same, I did saw B172K 33.7mm, but 0.1mm is smaller than my margin of error for sure.

[Chris_C]

I've not had a new set of 1.7 floats for a long time, but the 33.8mm measure does work. Have you tried reading through the green books? That gives a great explanation from memory.

The other issue is when the floats were made, and if there were made by anyone intelligent. With the changes to fuel since 85/86 when the 1.7 was thought about and launched in a 300 the make up of petrol has changed hugely and the density of the liquid we get now is different to that when the books were made. I.e, the floats are either more or less floaty for the same density of float in the different density of petrol, so it can cause some weird effects.

[morgan105]

Green books say 33 - 37mm, that's a bit of a difference.

[jtbo]

Green books say 33 - 37mm, that's a bit of a difference.

That is interesting, I have seen only 33.8mm and 33.7mm for Solex carbs, but indeed for B172 that is given as 33-37mm (or maybe green book is in error?).

why so broad range and why to give 33.8mm for B200 models if that is impossible with those too (or then someone has put B172 floats to my carb which is perfectly possible with somepoint of car's life).

I have Mac's B172K carb guide here, in that too 33.8mm is quoted and I don't think that Mac would put wrong value there or not know if there would be need for as large as 37mm because of float size variation?

This is truly a mystery that needs solving, so all members can know what is proper setting and how to know which is the reason why some floats differ in size such way that 33.8mm mentioned can't be used. Is it model year thing or is it just variation in manufacturing (hard to believe)?

My spare carb had smaller floats, that carb was on top of 240, that was older, than my MY88 360, is there a pattern of later model floats being larger and if so, why B200 greenbook has no mentioning of such?

Anyway with range of 33-37mm seannaayy is at the beginning square, with such large range one is as good as with no measurement at all and needs to do adjust a bit, test a bit routine until properly working level is found, I guess. If petrol has different weights today, then there might be also need to have adjustment to jets and emulsion tubes to get car work perfectly, so measurements and settings in books are probably not going to work at all and one needs to find jets that do work, which means it would be total pain to get thing to work.

Anyway it would be nice to really know this aspect as it would certainly help more than value which cannot be met or trusted.