Hey ho...up here in Canada it's getting cold out..my 1969 142s with dual SU's is running fine now, but everyone seems to mumble "better get those carbs set for winter!", so I'm asking now.

I'm quite mechanical, have the Volvo green manual and ain't afraid to try it out. What do they do to winter set carbs!!?? set them a little richer at startup?

I'm a 740 LH 2.2 graduate, but I couldn't pass up a car that was owned by a semi-looney University professor for 29 years, that comes with a stack of maintenence records, polishings, auto trans replacement, seat re-upholsturing and the like for just under $30,000 CAN over 30 years.

The car was bought for $4550 CAN in 70'and was appraised by the someone in 97' for ......you guessed it, $4550 CAN!

I hear they're EXCELLENT winter cars with their skinny wheelbase, good heaters. The 740T just might get parked for the chilly part.

Thanks in advance about the carbs..... Josh

there's a few of us with b21a 240s that have the single SU - aside from using the choke a little more there isn't much that needs to happen. mileage goes down with the winter fuel they give us, but the car runs fine with no change to the mix screw. The 240 gets a cardboard grille backing to restrict air to the rad, and I would double check that you have the highest temperature thermostat.
--
Stef (81 245 B21A SU M46 3.91) 327000km my volvo pages

SUs are the subject of a great deal of mythology, and the people who are telling you to retune for winter are passing some of that on to you.

There is a basis for that idea, however. The mixture carbs produce varies with air density -- denser air leans the mixture. All else being equal, cold air is denser than warm air. This does not mean that the air taken in by the carbs after the car has warmed up is significantly colder in winter, as it's coming from inside the warm engine bay and is heated going through the radiator. The engine itself does not want a richer mix in cold weather; you're only dealing with the carbs' ability to maintain roughly the same mix year-round.

I wouldn't change anything unless you start having problems. It's necessary to use the choke with properly tuned SUs for cold starts in any sort of weather, and the chokes should get you going in winter as well. You might need to warm up just a bit longer before setting out.

Phil,
I'm not sure that I agree with your rationale.
Denser air means a greater pressure drop in the carb = MORE gas sucked in
through the jet. Actually the density change is pretty small compared to
other factors since each degree drop only increases the density by the
inverse of the absolute (Kelvin or rankine) temperature, so the difference
between 20°C (293K) and 0°C (273°K) is only 293 divided by 273 or an increase
of about 7%.
The majority of the reason for enriching the mixture is
that cold gasoline and cold air lead to much poorer vaporization of the fuel
into the air and thus more difficulty in getting it to make a flammable mixture.
Gasoline is made more volatile in the winter to offset this somewhat. They
usually do this by blending butane and other more volatile hydrocarbons into
the gasoline.
--
George Downs Bartlesville, Heart of the USA!

George, I imagine you're right about most of that. I'm sticking with my advice not to retune unless you can observe a need to, though.

I agree 100%. Not broke = don't fix.
--
George Downs Bartlesville, Heart of the USA!

I think George answered it in a roundabout way pointing at what refineries do to fuel. A clean tank full of fresh winter blend fuel is what's required to make SU's run properly in winter. Sucking air from around the exhaust manifold might be helpful too. Stale fuel from last years batch of winter fuel is likely to make it hard to start because all the light ends that make it easy to start have probably evaporated.

Speaking of stale fuel.....

I'll soon be driving my new acquistion -- a 1969 144s -- a B20B with SU carbs fro Philadelphia to Easton, PA.

I am not (yet) apprised of how old the 3/4 tank of gas is.

No matter, I wouold like yoour advice on whether or not I would do well to add some cort of carb cleaner to the gas tank before starting out, and, what would you recommend (Berryman's?)

The car's been driven only around the block and started occasionally the past two years.

http://cgi.ebay.com/ebaymotors/ws/eBayISAPI.dll?ViewItem&item=4584193439&rd=1&sspagename=STRK%3AMEWA%3AIT&rd=1

I don't think you need a carb cleaner with SUs, they don't have any ports in them that are small enough to clog up. I would, take the bung out of the bottom of the tank & see what water & dirt or rust comes out the bottom, if the fuel looks clean as it comes out, put the bung back in & use it, but use as much as possible before getting a fresh tank. The fuel tank drain bung on carb cars has a 7/16"AF head & is tapered pipe thread, so it's very easy to put back in while fuel is coming out of it.

Got that RIGHT!!
--
George Downs Bartlesville, Heart of the USA!

I'm with Phil here 100%. Was gonna say about the same thing. Don't mess with the carbs until problems come up. Then perhaps enrich the mixture slightly, and also advance the timing a tad *maybe*. But don't do anything until it starts misbehaving.

If everything is in proper order, you shouldn't need to do anything at all. Keep in mind these cars were designed and built in Sweden. It gets cold in Sweden too.


--
-Matt I ♥ my ♂

I don't have a manual in front of me at the moment, but the only thing I remember doing to the SU's when it was due to get *really* cold (I owned a 544 in Fairbanks, AK), was changing the oil in the dampers to a lighter grade.
--
1971 142E ITB racer, 1973 1800ES, 2002 S60 T5