ACR B737-500 FLC IN AN ALTDEV. THEY OVERSHOT THEIR ASSIGNED ALT WHILE THE FO WAS OBSERVING BUILDUPS NEAR THE DEP RTE AND THE PIC WAS DISTR WITH AN ATC COM PROB. FO; PF; WAS WITH THE ACR APPROX 6 MONTHS.

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ON JUN/XX/97 AT XA18Z I WAS THE FO ON FLT DEPARTING IAH GOING TO IAD. WE DEPARTED FROM RWY 14L AT IAH WITH HDG 155 DEGS ASSIGNED AND A CLB ALT OF 4000 FT. I WAS THE PLT AT THE CTLS AND THE CAPT WAS WORKING THE RADIOS. AS WE WERE CLBING OUT FROM HOUSTON; I NOTICED THAT THE CAPT WAS HAVING PROBS TRYING TO GET A HDOF FROM THE CTL TWR TO DEP CTL. I WAS HAND FLYING THE ACFT AT THE TIME AND NOTICED A CUMULUS CLOUD AHEAD OF US AND WAS PLEASED TO SEE THAT OUR PRESENT FLT PATH WOULD CLR THAT CLOUD. THE NEXT THING I HEARD WAS THE CAPT SAYING 'ALT' AND SO I LOOKED DOWN AT THE ALTIMETER AND NOTICED IT PASSING 4200 FT AND SO I PROMPTLY TOOK CORRECTIVE ACTION TO CORRECT TO OUR ASSIGNED ALT OF 4000 FT. THE MAX DEV THAT I SAW DURING THE EXCURSION WAS 4400 FT. THE REMAINDER OF THE FLT WAS UNEVENTFUL. I THINK THAT THE CONTRIBUTING FACTORS IN THIS EVENT WAS MY FIXATION OUTSIDE OF THE COCKPIT; AND THE CAPT'S PROB WITH NO HDOF FROM TWR UNTIL NEARING 4000 FT. IN THE FUTURE I WILL CONCENTRATE MORE ON THE DEP PROFILE AND LESS ON CLOUDS.