[Roadsters] How to warm up a Roadster?

[Gary McCormick]

Technically it is not a choke, as it does not physically restrict airflow to produce a richer mixture, but functionally it does the same thing, just bass-ackwards because of the way these weird ol' carbs work!

Gary McCormick
San Jose, CA
'70 2000 SRL311-13291

Paul <9laser3 at bright.net> wrote:   Did everybody forget that roadsters with SUs do NOT have real 'chokes'.
Pulling the choke handle only lowers the needle seat making a bigger opening
for fuel to the venturi, richening the mixture.

Paul
Ohio

----- Original Message -----
From: James Fogg 
To: 
Sent: Thursday, September 27, 2007 4:02 PM
Subject: Re: [Roadsters] How to warm up a Roadster?


> > -----Original Message-----
> > From: Mark Dent [mailto:mark at dealermats.com]
> > Sent: Thursday, September 27, 2007 3:20 PM
> > To: James Fogg; datsun-roadsters at autox.team.net
> > Subject: Re: [Roadsters] How to warm up a Roadster?
> >
> > Opening the choke does not lean out the mixture, it richens it.
>
>
> I'm not sure how you figure this. From the perspective of the butterfly
> valve, pulling on the choke handle closes the valve. Pushing the choke
> handle toward the dash opens the butterfly valve. When the valve is
> closed the fuel ratio is enriched because of greater vacuum in the
> venturi. Since air is easier to "pull" than fuel and the carburetor is
> set up for a certain balance of air/fuel, if you block the air entry
> (close the choke) you change the balance of fuel to air.
>
> Everything I've been taught says you enrich the air/fuel mixture to
> start a cold engine.
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