I recently smoked a pork shoulder in a weber charcoal kettle grill and I had a lot of trouble maintaining the temperature. Are there any tricks to using a mix of charcoal briquettes and wood chunks for smoking like this?
A couple of suggestions to help maintain constant heat.
Time it such that you are only adding a little fuel at any one time. Adding half new fuel will cool down considerably as it has to catch, burn, etc. Adding 10% fresh at one time is much better, for example.
Conversely, if you're lookin' you ain't cookin'. Open as little as possible. Remember there will be a lag to any specific change. If you change the vent, look at the temp after 5min then after 10min to see if the trend is up or down, and if it is accelerating or slowing. Use that as a guide to your next change.
Thermal mass is your friend. Get yourself some appropriate stones, bricks, etc. If you have any room left over from your fire and meat; fill the space with the bricks. They will help to smooth out the heat from open/closing as they take up space that would otherwise be taken by "cold" air when you open to refuel. Obviously you need to not block actual ventilation.
Overall the kettle is a nice grill; but leaves a little to be desired for smoking. The offset firebox style where you can refuel without disturbing the cook-box has a definite leg-up primarily for the refuelling reason; but with some practice you should still have wonderfully edible results with the kettle.
I'm assuming you're talking about hot smoking rather than cold smoking.
Thin steel is a good conductor of heat, but a poor reservoir. What this means is that the temperature inside is going to track very closely the amount of heat being produced by the briquettes at the time. This is fine for fast cooking, but for a long slow cook, you want stability.
One suggestion would be to add thermal mass to the system by putting heat reservoir objects into the grill, and letting them absorb and steadily re-emit the energy from the charcoal. Stone and ceramic are both options.
The other suggestion is getting the charcoal to burn at a steadier rate. Try adding smaller batches of charcoal more frequently.
A couple of things that I saw on some of the posts. Do not add unburnt fuel to a fire, when you are smoking. This imparts a bitter flavor, while pork hides it some, a experienced BBQ'er will taste it immediately. On brisket and beef ribs, it will ruin it outright and make it inedible. As well you should let the fire burn until the smoke is almost clear vapor and is not bellowing smoke before you put your meat on. You should see wiffs of blue and gray smoke in the vapor this will impart a smooth smokey flavor into the meat. If you have to add fuel during the process, burn the fuel down until it is white ashed on all of it surface in an external vessel such as one of the charcoal burners or a smaller grill.
The recommendation on putting a water pan over the fire, is good advice for direct heat where the meat sits directly above the fire. The reason being that once the grease starts to drip on the fire it is inevitably going to flare up and cause the temperature to skyrocket and meat to burn. Ensure that the pan is larger than the meat, so that it can catch all of the drippings and make sure that you keep water in it at all times. Adding some cider vinegar and apple juice will impart a nice flavor as well.
Ideally if you are going to do any amount of smoking on a regular basis, you should invest in a smoker that has on offset box, smoking on a grill is always a more difficult proposition.
Try the "Minion Method" (Google it) for maintaining your fuel. It's a method where you have a bed of unlit coals to which you add a few lit ones. The lit coals provide the heat, and the other coals slowly ignite throughout your cook. Once you get to your desired heat, it is easy to control with the vents on the bottom.
Don't worry about the unlit coals igniting. As long as you're not using match-light, you won't experience a problem with impurities being cooked into your food. The new Kingsford Blue has fewer and cleaner fillers. Even better, use lump or coconut charcoal.
For more information on the Minion Method, check out The Weber Virtual Bulletin Board (link text). They have a section devoted to the method on the site, and you can find plenty of help in the forums on maintaining temperatures.
For maintaining the same temperature in a kettle grill for longer periods of time the following works well:
Take briquettes and form a circle that has a gap somewhere. How wide and how high you stack them determines the resulting heat, but two deep and one on top is a good starting point. If you light the ring on one side of the gap the charcoal can slowly burn around the ring resulting in a more or less constant temperature for several hours.
A friend of mine, who taught me this technique uses it for pulled pork.
For smoking the wood chips can be placed on top of the circle.
In case my description is unclear (I'm no native speaker) perhaps this picture I found on a google search helps clarify.
I hope the pics are shown, the computer I'm on blocks imgur so I can't see them.
The short answer is, you're always going to have trouble controlling heat in a weber kettle grill.
The longer answer: You can put out some great meat with it. As a practical suggestion on top of the posts above, I would suggest you
1) move all the meat to one side of the grill,
2) put coals on the other side of the grill
3) put a metal water pan above the coals to keep the heat even
4) make sure that the vent is situated above the meat, creating a flow of air from coals over across to the meat.
5) get a wireless thermometer setup for grilling
6) using that, adjust the air vents (start with the bottom vents at half open and top at full as a baseline, close them down as needed to lower temperature).
Enjoy your smoking!