OK Pontiac guys I need your help.  I've got an opportunity to buy an old engine that was kept in storage by a deceased hot rod guy but for the life of me and my friends we can't determine if it is in fact a poncho engine or what. I know it is a BOP because it has GM on the intake and the starter is on the driver side. How can I further ID this engine as to Cubic inch? I looked for casting #s on the rear of the block but didn't see any. Please help.  

There are lots of Pontiac web sites that tell you where and what to look for. WWW.Pontiacpower.net is just one of many. You should be able to find enough info there to determine if it is a Poncho and what displacement it is. Good Luck.  

C'mon pontiac guys. You want to tell me where to go,like everyone else, but can't tell me where to look on the block for like casting #'s.  We Chevy guys can tell you right quick where to look and what you can expect to find and tell you in a flash what it is.  

i would suggest my dads site www.wallaceracing.com he has all kinds of code searches and calculators.  

Depending on the year of Pontiac Block the side will have the last two digits of the displacement on it. "55"=455, "00"=400 "28"=428. I don't believe the 326 or 350 had those marks (I could be wrong).  The key to really identify Pontiac Blocks if you don't want to look else where to check serial numbers is to measure out the bore. The stroke would be one of three 3.75",4.00" or 4.21" but the bore would be the defining detail.

There are two letters at the front left side of the  block that "help" identify the block, but you have to know the year of the block for it to be definitive, as an engine code for one year would be 400 and a later year be 350.

And you are positive it's a Pontiac Block? GM on the intake and starter on the right hand side is hardly a definiative description of a Pontiac block (Chevy and Olds can be described the same).  If the front and back of the block where the valley pan goes is curved, that's definiative for the block. As is the way the water pump/timing cover connects to the intake manifold, as is the intake manifold its self.  

pontiac began casting displacements in the sides of the block in the late 60's. Between the middle and last freeze plug.  it started with the 428's in 1968. then with the 455's in 1970 when they replaced the 428's. for the 350's they started in 1970 in the front side of the block, while all 1971 and later 400's got the same.   1965 and later blocks got a 2 letter code just below the passenger head in the front signifying the original application. codes were reused  so you need to find out which year it was made.   the block date code is found to the left of the distutor hole. B059= feb 05th 1969.   OH they also put engine size under the valley pan on the lifter valley ribs.  28 for 428 55 for 455 and 00 for 400