My question relates to size,year and model of following pontiac engine in my 68 firebird engine number clearly shows

hi,im lightsout22 and i think i can help you with this. the h198 is a good number. the h is the month the engine block was made, the second number is ***** day, which is the19th. the last number is ***** year which would be 1968. the pre 1970 engine had 2 motor mount holes on each side. the 1970 and newer has 5 holes per side. if you go to wallaceracing.com, you can get all the pontiac engine info you need. i can tell you though that it is a 1968 block, and it more than likely is a 400 c.i. i hope this helps. if you need anything else, ill do my best to help. please dont forget to rate my answer if you are happy with my service, so that i recieve credit for helping you.

larry, this number is ***** considered an engine stamping code. since it is stamped on the block and not cast into it. however, i have found more information, i dont know if you will be happy about this or not. first, this is 100% without a doubt a 400 c.i. now, the YD identifies the engine as a 400 c.i. and i can tell you that this engine was used in 1967 and 1969 in fullsize pontiac cars, excluding GTO. the GTO had a different stamp. for a 1968 firebird the 400 engine codes were: WZ, YT(H.O MOTOR), WQ, YW(RAM AIR 1), WI, XN(RAM AIR2), WU, AND XT. now, in 1973 the YD was used to identify the 455 c.i. big block. from what i find,i believe the numbers there are a partial vin code from the car this engine was in originally. your 400 is 290hp, 10:5 - 1, 2 bbl. I may be able to find more info if you need it, but if you do, try to send more pictures of this engine and the rest of any numbers on it. the photo helped quite a bit.