Originally Posted by b-man (Post 6450921)

1969 was the year the factory began producing some exhaust manifolds without the end bolt holes. I guess they decided they could save money that way, usually that’s the reason.

In 1965 both the manifolds and heads had all 6 bolt holes but they assembled the manifolds to the heads using only 4 bolts, there are pictures of 1965 GTO engines built that way sitting and waiting at the factory.

Usually the big-valve performance heads would have all 6 bolt holes drilled and tapped (1969 #62 & #48) but the low performance small valve heads (#46 & #47) had all 6 bosses cast into the head but only 4 were drilled and tapped.

Even some of the round-port heads (1971 #197 & 1972 7F6 455 HO heads) had only 4 bolt holes drilled and tapped, if you want to run headers you have to drill and tap the end bolt holes. The exhaust manifolds used on these heads were held on by only 3 bolts if that doesn’t sound crazy, the way the manifolds were cast only allowed for one bolt for the center two exhaust ports.

In a nutshell the factory didn’t give a damn if headers would seal or not, the exhaust manifolds sealed up fine with 4 or even 3 bolts in some instances.

Originally Posted by grivera (Post 6462976)

My 1969 47s have bolt holes on the ends. Should I assume they were added?