+1 as previously discussed I believe in a number of other threads.
Don't think we've ever looked at the amount of time between the two or compared them in a discussion. Since one can not be easily seen I guess there has not been much interest. Possible subject for another investigation and discussion. Not sure how much data points can be found given we would need to focus on one engine plant
I cannot tell you about six bolt block engines but five bolt High Performance 289 engine assemblies from the Cleveland engine plant 1963-64 the engine assembly date is usually the same date as on the oil pan rail but it could be a day or two later. I have not myself seen more than one day between the two dates on five bolt HP289 block assemblies. For five bolt block engines assembly date means a lot as Ford changed ancillary parts often in 1963-64. Ignition distributors, carburetors, cylinder head castings, spark plug wire revision levels, timing cover castings, how blocks were specifically machined, block engineering numbers, and etcetera used depend on stop and start dates for different designs and or revision levels. It has taken decades to get a good grasp of all the running in model year changes. Some clues can be found in factory training manuals and year MPC files but beware that a MPC published at a later date will drop some information. Ford made so many running changes I am still not sure how five bolt HP289 engines were configured if assembled in the roughly six weeks of June and half of July 1964.
I field questions from Cobra owners trying to return what is left of their original engines back to day one specifications. With changes at the Ford Cleveland plant, something always changed in the April-May time frame, sometimes in June, sometimes in September, in December 1963, and in February 1964. The engine assembly date is the key to understanding how any given five bolt HP289 engine was completed.
