help, zeniths, choke cover issue

[deQuincey]

hi

as i probably have mentioned before i am trying to build a second set of zeniths, to be able to compare these new ones with the original set that is actually on the car

the reason is that i can not tell if the actual situation and performance of my carbs is the best possible one. and if the result of this second set is the same, i will put them on the shelf for future harder times

antecedents:
it has been virtually impossible to find a pair of the exact type of my zeniths.
instead i found a 3.0CSA set in the UK, and the most promising 3.0CS set in madrid, but these last ones were partly broken due to a bad decission of the PO about how to store a engine ( the intake manifold facing the floor:shock: )

so, i am trying to build a correct set using parts from these two sets plus the older set i bought from a 3.0CS USA version

the body and main parts will be taken from the UK 3.0CSA set

situation, choke covers:
i mean the parts that contain the bimetallic circular spring that is heated by the coolant and by the electric resistance

again i have three sets of these parts, two UK, two madrid, two USA, and they are in different condition the best ones are the USA ones, but here it comes the difference and the question

when you meassure the electric resistance, you have 30 Ohm in both the european ones, and 15 Ohm in the USA ones

according to the blue manuals the EU ones should be 20 Ohm and the USA should be 15 Ohm, but there is no explanation for this difference

questions,

does anyone know why there is a difference in the specifications between usa and eu ?
why ? or what is the effect of this difference ?
do you think that i can use the usa spec choke covers in my EU carbs ?
if doing so which can be the difference in behaviour expected ?

thank you in advance

 

[deQuincey]

rethinking this issue

according to a simple electric law, for a certain voltage, the lower the resistance value, the higher the temperature reached

so for 15 Ohms (USA version) the temperature reached in the solenoid will be higher than in the EU case (30 Ohms)

i have no certainty but i assume that the temperature will be reached faster in the USA case than in the EU case, too

so that means that the choke butterfly will open earlier in the USA than in the EU

consider that the electric solenoid ads heat to the choke cover since the car is started, helping the cold engine to warm up

when i say add heat is because the main heat is given by the coolant passing through the adjacent chamber of the choke cover

i know i am solving none of my questions, but only giving more facts...

regards

 

[61porsche]

electric choke values

DQ,

Part of the answer is yes, you can use either. The only difference is that your reference mark may shift on the cover and perhaps the USA releases slightly earlier for presumably emissions. But BMW also used differing ohms for displacement. ( 2800, 3.0, 3.3 ) I've never found the difference to be critical or noticeable since there are many cars with replacement engines up to 3.5s.

Just use the same value on both carbs unless you're really in a pinch.

I hope that this helps.

 

[deQuincey]

yes, thank you jerry, that was my idea, use the same value in both
and thanks for your comments, it seems sound to use one or the other
emissions ?, yes probably, i can not find any other reason, trying to complete the "rich" stage as soon as possible
thanks again

 

[roundel]

Zeniths

I have several ssets of these carbs (somewhere...) that are almost new & have been stored for almost 40 years. Obviously the rubber elements would need to be replaced but the hardware, spindles, linkages, etc...will be perfect.
Located in Sussex, England.
Alex

 

[deQuincey]

a question on the thermostart valve

hi

there is a doubt about the electric installation of the thermostart valve (see the pic to identify it)

you know that zenith carbs were apparently similar, but very different in the details, the set that i am repairing now has a lateral thermostart valve, it seems to work well, so when i connect it to the battery it starts warming up and opens the tiny valve attached to it

the question is the following: is this valve always open when the car is working in normal conditions ? and the more important thing: is the electrical resistance always ON and heating ?

according to the installation drawing it seems so:

apparently it is connected to the same point where the iddle shut-off valve is

can anyone confirm this ? i am preparing the wiring right now

regards

 

[Tony_V]

I think it should only be open when the engine is cold.

 

[deQuincey]

I think it should only be open when the engine is cold.

thank you for your input
unfortunately i can not agree, according the manual it is closed when the engine is cold and the outside temp is below 15 ºC, and then the electric resistance starts warming it up and it opens

so the hot makes the opening, i can not think that it will close again if the engine is warm, and moreover you still feed the resistance with electrc power