Does anyone elses B20 NEED to have the choke used for the first start of the day no matter what the exterior temperature? I kind of figured that if it is over 70F the need for the choke would be supurfluous .... My son's B21 in his '78 242 is the same ..... is this some sort of a cruel Swedish joke ? After that first warm up of the day choke is no longer required .... what's the deal ?
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Brett Sutherland & the 1.5 million mile 122 CANADIAN www.ecvintagevolvo.com

Coming from a wet part of the world (England), I find that relative humidity is a bigger culprit than the air temperature in needing choke or not. A warm and wet spring day requires it, but a dry winter one doesn't. Am not a physicist so I'll leave others to explain that...

Every old Volvo I've had required the choke IF it was tuned properly. If the carbs were set way too rich, then it wouldn't be necessary...

On weber equipped cars, its not so necessary if reasonably warm... just have to mash the throttle a couple times and the accelerator pump dumps in some extra gas, but not so with SUs.

I wouldn't worry about it... sounds fine to me.

-Matt
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-Matt '70 145s, '65 1800s, '66 122s wagon, others inc. '53 XK120 FHC

Logic tells me that the SU needs an extra shot of gas for the startup process, since there is no accelerator pump or dash pot to provide the increased fuel volume needed. Lowering the fuel needle provides the richer mixture and opens the venturi butterflies for the extra air needed for initial combustion (fast idle). Once combustion begins, the SU's operating vacuum is established and the choke can be turned off.

Even a fuel injected Volvo uses the cold start valve to achieve the same results all year round. A fouled cold start valve can prevent the engine from starting, causing the primary injectors to flood the engine, even in the summer. A faulty fuel pressure regulator can cause a similar malfunction and flood the engine. It's just that we don't have to do anything with a fuel injected engine, but it's still a similar mechanism.
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Cam a.k.a. CVOLVO.COM

Always that way for me, regardless of external temperature. Warm, the SUs seem more likely to be rich than lean on startup. Once run, the engine holds heat for many hours. I would still need choke after a it stands a few hours in the winter, though.

Not a cruel joke, just another way of letting you stay involved with your car...

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67 144, 86 740T, BMW R69S, R60/2

I believe if it were otherwise you would have a slightly (or more) richer
mixture than needed for optimum running. In fact for optimum fuel economy
(more of a concern to the "Nova" Scottish than to the Gringos in Oklahoma)
you might want to lean it some more to where it is a little cranky till it
is really warmed up. But that hinders driveability, especially if the car
is mostly used on short trips. The cast arn combined manifold is friendlier
in this than the aluminum intake manifold.
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George Downs, Bartlesville, Oklahoma, Central US

It has the Cast ARN manifold .... and it IS cranky until fully warmed up ... guess I should be thankful that since the rebuild the warmup takes MUCH less time than before ....

Brett
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Brett Sutherland & the 1.5 million mile 122 CANADIAN www.ecvintagevolvo.com

I see on jc whitney (ebay, etc also) some sort of aluminizated tape for cover the exhaust manifold and prevent hot temperature on the engine bay. Using it, and by the same token, the hot temperature remain into the manifold... if your has inlet and outlet manifold interconnecter (the hot plaque), could be usefull to cover with that tape the exhaust manifold to promote the heat transfer without heat loss on air.

(my excuses for using spanish phrases with english words).

Joaquin
Rojo 121 Amazon
Lima Peru
(12 to 30 degress celsius all year, I use the choke or press 2 times the accelerator for saturday starting - by now I use the rojo only on weekends)

If it is bothering you you could always set it a notch or two richer.....
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George Downs, Bartlesville, Oklahoma, Central US

LOL Iain says .... Fuel injection will fix the problem ..... Just waiting for the financial gods to smile ..........

Brett
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Brett Sutherland & the 1.5 million mile 122 CANADIAN www.ecvintagevolvo.com

Besides... I'm TOO Scots to richen the mixture .... I've already purchased a new choke cable .... now if I can just get that damn Phillips screw to loosen under the dash that holds the casing in place I'll have the problem solved in a flash ...Well just about time to hit the road for the "CHICKENBURGER" it's ECVVC Meeting night !!!!
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Brett Sutherland & the 1.5 million mile 122 CANADIAN www.ecvintagevolvo.com

Besides... I'm TOO Scots to richen the mixture .... I've already purchased a new choke cable .... now if I can just get that damn Phillips screw to loosen under the dash that holds the casing in place I'll have the problem solved in a flash ...Well just about time to hit the road for the "CHICKENBURGER" it's ECVVC Meeting night !!!!
--
Brett Sutherland & the 1.5 million mile 122 CANADIAN www.ecvintagevolvo.com

Besides... I'm TOO Scots to richen the mixture .... I've already purchased a new choke cable .... now if I can just get that damn Phillips screw to loosen under the dash that holds the casing in place I'll have the problem solved in a flash ...Well just about time to hit the road for the "CHICKENBURGER" it's ECVVC Meeting night !!!!
--
Brett Sutherland & the 1.5 million mile 122 CANADIAN www.ecvintagevolvo.com

It was always that way for me if the carbs were tuned right. I don't know why it's not necessary later in the day, even if the car's been sitting for hours and has cooled off apparently completely.

The iron block and the mass of fuel in the tank both absorb/lose heat slowly. That is they retain whatever heat or lack of heat they have for a long time.

After a nice cool night everything is still 55-65 degrees in there. After a run and shutting down everything maintains a higher than ambient heat for a long time (water in radiator won't but that is the point of the radiator, right?).

There you have it!

Sometimes cranking with the pedal floored and "snapping" it closed will give a small "burst" of fuel to get the engine started. But you have a choke, so...

Mike!