OK, I did my conversion today and cooked on it tonight. Works great! Many thanks to
Ira B, Canadian gas fitter who gave us this excellent instruction:
http://tvwbb.com/showthread.php?49713-Weber-Q-low-flame-or-no-flame&p=542185&viewfull=1#post542185
Since people seem to have trouble finding the single part that will get this done and put together several which will work, but which also increase the potential for leaks, here are my parts links again.
Amazon is also your friend. Here is the single adapter part needed, 3/8 male flare, 1/8 female pipe ...
http://www.amazon.com/exec/obidos/ASIN/B006PKK3XI/tvwb-20
My parts arrived during the week and today I did the swap, here is the procedure with step by step photos.
http://www.amazon.com/exec/obidos/ASIN/B000KKNZKC/tvwb-20
And gas tape is thicker and denser than plumbing PTFE tape. It is yellow, not white, and not expensive. I got a roll at Home Depot, but had I thought about it I could have added it to the Amazon order.
One thing to be careful of is to get the right regulator! The whole reason for doing this is because the regulator on the Q grills does not work that well with 20 pound tanks and a long, unregulated hose. So get a hose
designed for a grill not for a turkey fryer or large flat griddle or something else. Mine was optimized for a grill. Sorry it is sideways, but you can see it is a grill hose on the box.
Remove the Q cooking grates and then the burner tube. I used a 3/8" socket wrench.
Then pull off the control knob and remove the lock nut holding the valve in place. A 5/8" socket fits the nut, but I just used a slip-joint pliers.
The valve is attached to the regulator which is attached to a metal heat shield bracket. Just push the valve back through the hole then swing the assembly down and the whole thing comes right out. The heat shield fits a slot, it is not fastened in place. Here is what you are left with.
Remove the heat shield with a 1/4" ratchet. Now you want to remove the regulator from the valve, and it is on there TIGHT! I put the valve body under my heel on the deck and loosened the regulator with a pliers. Be careful not to put pressure on the brass valve stem! Getting it started is tough, but once it breaks free you can twist it off with your hand. There is some red sealant on the threads, brush that off with a dry toothbrush. Here are the valve and regulator, separated. I put the regulator, small screws, and heat shield in a ziplock freezer bag in case I want to convert back for any reason.
Now you want to put some gas tape on the threads on the valve body. As Ira B cautioned, do this carefully so you don't have tape hanging into where the gas will flow, and wrap it around clockwise so it will not unravel or bunch up as you screw the fitting on. Here are my taped valve threads and the single adapter fitting. Really, if you cannot find this part at your hardware store, order it from Amazon, it is worth waiting for instead of the ungainly long series of parts I've seen others use. This is (a little) safer and a more elegant solution.
I twisted my adapter on by again putting the valve body under my heel on the edge of a deck stair and tightening it on with a wrench. Be careful not to put pressure on the brass valve stem! If you have a channel lock pliers you might want to use it to hold the valve body and wrench the fitting on. It should be tight but not gorilla tight. Here are the joined parts.
Now attach the regulator hose, no tape needed, but snug it up tight. Then insert the valve back into its bracket and reattach with the lock nut being careful to ensure that the control knob indexes properly when replaced. When you have it where you want it, snug the locking nut down tight. Reattach the burner by slipping it over the regulator and tightening the machine screw with your 5/8" ratchet again.
Now attach your tank and with the grill valve off, open the tank valve. Wait a few minutes and see if you can smell any gas. Then use a 50/50 dish soap and water solution and apply it to the valve, adapter and hose fitting (I used a sopping sponge, you can use a brush or spray bottle) and check carefully for leaks by watching to see if any bubbles form.
If not, open the grill valve and light it, checking to see that the burner is evenly lit and the flame ranges from high to low properly. You should be good to go! Here is my new setup!
Did a steak on it tonight, works great!