[steelcomp]

I don't want to get into an arguement here, but you don't want to change the 660's jetting 10 sizes. You can't compare the two carbs. The 76 jets in the 660s is the stock jet size for that carb. If there are removable jets and a secondary metering block, someone has modified these carbs, but the stock secondary metering plate, as it were, was equal to a 76 jet size, so there isn't really any difference as far as stock calibration. These carbs out of the box are set up a little "fat", as to be safe. Remember, a carb is calibrated to provide a certain amount of fuel for the given size and metering of that carb. Although the 600 vac. secondary carb is similar in size, and the primaries are almost identical (ventury sizes the same, throttle plates a little bigger on the 4224) the callibration is completely different, mainly because the 1850 runs a power valve. This is worth about 6 jet sizes. (If you were to remove the power valve from the 1850, you'd need to go up to 72's)

Do these 4224's have idle mixture screws in the secondary metering blocks? If so, they've been converted to four corner idle, which will help, if you choose to use them. (and they were done right)

Bottom line is, the best place to start with any carb, even if you're running multiple carbs, is to start with the stock setting(s). Make small changes, and make one change at a time or you'll never know what change had what effect. Document your changes in minute detail. What ever you do to one carb, do to the other. Don't buy any more carbs or anything else because they seemed like a good deal or for the bad boy effect. There's a reason someone is getting rid of them. When carbs get modified, it only takes one hole in the wrong place, or one wrong part to turn an expensive carb into a paper weight. The "bad boy" effect won't be so bad when you try and drive these carbs, and they stumble or fall on their face untill the motor catches up, and the guy next to you is GONE! To put it bluntly, these are the wrong carbs, and you're going to spend a lot of time and frustration trying to get them to do something they aren't designed to do. And milling off the air horn dosen't really help anything. Some say the flow bench will show the opposite. But it looks cool.

BTW...I'm not sure what manifold you have, but make sure the (660) carbs, with the added secondary metering block, will fit. they might not.