well it's been chilly here in minneapolis (-7 F last night); anyway she's starting fine runs ok if i keep the choke pulled just a little, but my question is really how do i preheat SUs? was thinking of trying to find a late model air filter setup and run a tube near the exhaust manifold; but i was wondering if there were any other solutions to preheat my carbs.
i saw some MG cannister style air filter assemblies on ebay, they looked like they might work, any suggestions?

It's not necessary to heat the carbs per se. What you need is heated air. You can do that either to the air as it enters the carbs, or after. The late integrated iron manifold is best for smooth running in cold weather - in Canada it gets cold a lot....
The pre-heated air is also a good idea, although the manifold heat should be enough.
A viscous drive fan is a great idea too, and blocking some of the air into the rad is as well.
A good block heater, and 10W-30 or even 5W-30 synthetic oil will make the engine perform like a summer day. I run 5W-30 in my B23A year round, no air pre-heat, with the stock water heated intake manifold (and a 188 thermostat) that the OHC engines use. No problems. With the integrated iron manifold you'll have the best luck. The aluminum manifold is not the way to go.
It's a Volvo after all - from a cold land...

When I bought my new ’66 Amazon I lived in Prince Albert, Saskatchewan where -40 (C or F, take your pick) was not uncommon in the winter. A block heater, a heated plate under the battery, a chunk of cardboard over the rad with a 6” hole in the middle, and the lightest oil you could find was the formula for winter starting success and creature comfort. The biggest issue was seeing through the ice fog while on the road. :-)

Properly tuned and prepped these babies will start and run quite nicely in winter’s worst.

Cheers,
--
Barry -- 1967 122S 'Betty'

It's often recommended to drop the jets a couple flats if you run the car regularly through the cold part of the winter. For short journeys you can part block the front grille with cooking foil. Does the same job that the radiator blind did on the early Amazons. There should be a rubber "flap" threaded on the hose on the front carb to stop the cold air blowing straight onto the float chamber. It's usually missing.

the later combination style exhaust manifold is supposed to to the pre-heating function. It works okay, but something closer to the later volvo setup with a steel shell around the manifold that leads to the air filter might work better.

I was using a pair of 140-style HIF6s that had a 3" hose on the air filter box that went down towards the manifold, so I'd guess that there is a 140 manifold shell that might be just what you need.

Then again, I may have mis-interpreted the function of that hose...

There used to be electric heater rings that would fit around the domes of SU's; I believe they were to prevent carb icing, but they would probably heat the oil in the dashpots too and make it less viscous when carbs were cold (faster throttle response).

Bill

One method of getting heat to the carburetors is to make spacer blocks out of aluminum to mount between the carbs and the intake manifold. Make it of sufficient thickness to allow a generous hole to be bored through to pipe engine coolant.