Can I use these cans with a Iwatani torch ( as used in torching food or use in encaustics art) ?

I use it with this torch http://amzn.to/2H0i0VV Worked perfectly

Hi. Are these 4oz or 8oz? How many grams? Do they have a notch around the rim to fit into the portable cook stoves? Thank you.

8 oz (227 grams) There is notch in the rim. We bought these to go with the portable cook stoves we gave our married children for gifts.

Does anyone know if these will fit the "Max Burton" single burner stove?

Yes, if you are referring to the camping stove.

Does this fit Coleman instastart stove

Took a quick look on the Internet to see what an Instastart stove was, and from what I saw, I can't be sure which one you are looking at. Several Coleman stoves were called Instastart. Depending on which stove you have, you may need the small green propane tanks/cylinders (approx. 16 oz) that you see more often, depending on which type of fuel the Instastart stove requires. The green propane style typically attach outside the stove. As for these canisters, which are butane, they work in the little stoves where the can is completely enclosed behind a hinged door in the stove when it operates. These canisters look a lot like a can of cooking spray. They are about 8 oz.So you'll need to determine which fuel / canister your Instastart requires.