UDC =Upper Dead Center
the BB is set at 5 degrees before UDC

5 degrees before UDC is where you want to set the distributor for a stactic timing. Leave the distributer clamp loose so small adjustments can be made while you crank the engine over.

OF COURSE THIS WILL BE DONE AFTER A COMPRESSION TEST.

Below is a link to the 1955-1959 GMC maintenance Manual. This online source gives specs and tune up sequence for the gmc 270 and 302 motors. The 228s aren't much different, so these spec's will be close. Best bet for you would be to get the Maintenance Manual for your specefic truck.

http://chevy.oldcarmanualproject.com/gmc/5559mm/5559mm365.html

From previous posts, there was an uncertainty to which engine you have, and if your truck was American or Canadian.

Have you confirmed your engine is a 228 or is it a 216 as was used in Canadian trucks, or some other motor that has been replaced by a previous owner?

John

Edit: I just saw your video and pictures of your engine. Your motor is not a 228 GMC. It is very likely a 216 Chevy motor as was standard equipment on a Canadian GMC trucks. As such, the specs for the GMC motors I linked will not due you any good. Search for the timing spec's for a 216 chevy motor. The BB should be close enough for static timing on the 216.

Last edited by bigbadswingdaddy; 05/24/2011 8:54 AM.