Join Date: Jan 2015
Location: Injun Territory, 'Merica!
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The partial VIN was stamped in a gang stamp fixture and occasionally is stamped fairly light or deep on one end then trailing off to lighter stamping on the other end. The stamping is, typically, close to parallel to the passenger side of the timing cover, relatively low on the block face. if its a Fremont built car, look higher up on the machined face of the block, its often cocked at an angle. On any other plant '68+ model Pontiac V8 block, with the engine in the car, you may need to remove the lower radiator hose from the timing cover, and use a a small tooth brush sized wire brush on the face of the block in the above noted area.
'YS coded 400 engines were most common installed in '67-72 GTO's and many were pulled over the years for one reason or another. Have owned several 68 YS coded engines out of partscars, and eventuallly all of those '68 YS blocks ended back up in other '68 GTO's being restored. Many of us vendors have offered for sale close dated blocks in a similar manner for decades, so it is smart if you have the PHS invoice copy on a '67 to mid year '68 Pontiac to ck the assembly number of the block above the two letter code, YS, to the number in the little box noted engine unit number on the copy of the IBM card.
It also makes sense to look for the partial VIN, though these on occasion were not stamped. Also ck for the correct 68 model 16 casting heads with screw in studs. Their casting dates should mirror a range close to that of the date of the block. The alpa numeric block casting date is back by the distributor hole. Many '70's and early 80's driver GTO's and Firebirds 400's got later lower compression heads swapped on like '71 casting 96's, 4X's, 6X's. If the dates on the 16 casting heads turn out to be late '69 or dated in early to mid '70, the heads most likely have been changed to '70 model small valve 16 heads...the casting number on these appears different...have seen it before. In that case, also easy to pull the valve covers, look for screw in studs with the steel guide plates bolted under the flared base of the rocker studs. The small valve 70's 16's were press in stud. Best to you documenting the engine.