Normally in precision, your 2H inquiry sets trump (tentatively -- the 1C bidder can mastermind later); now a 3C bid would ask pard what round control he has in the suit, and you could, among other things, avoid getting too high when you have two quick club losers. The answers are in steps, so 3D = Jxx or worse, 3H = third round (queen or doubleton), 3S second round (K or singleton), 3NT first round, 4C better than that (depends on your agreement, but AK for sure, AQ maybe/maybe not [yes, the way CC Wei originally wrote it], void maybe/maybe not [no, iirc, in CC Wei precision]). Here, he'd say 4C, and you'd then make the same inquiry in spades, allowing you to bid a safe grand when he holds a doubleton spade or the queen.
Lacking that tool, I'd do some control bidding before toting out blackwood -- i.e., if a 3-level bid is not a conventional asking bid, but rather a natural bid, I might try 3S, hoping to hear 4C (as I would in this case -- I'd follow with 4D, and then ask for aces over any signoff, hoping pard will work out the importance of the spade queen). It's even possible you could hear partner get excited about spades, suggesting Qxxx and making 7NT pretty safe.
On the actual auction you're not in enormous danger of going down if you get the wrong answer to 4NT, but you're forced to guess about the grand. Most people would say that with a ten-card trump fit including AKQ, and no first- or second-round loser in any side suit, you should be bidding a grand. It will have no play if partner holds xxx QJxxx xx AKx, but that would be pretty bad luck, and with even slightly more there may be a spade/minor squeeze.
Note that you have to do all this even if you play that the 1H positive response is limited to 13 HCP, as many do (with 2H showing any 14+, or a more sophisticated version). It's pretty easy for him to have the spade queen, making a grand a good bet, but even opposite as little as xx Qxxxx xxx AKx you are cold for 7H.
Also, if you're using 1430 it's probably time to switch to showing specific kings over 5NT.
Last edited by atakdog; 01-31-2009 at 08:33 PM.