Posted September 01, 2012 - 08:34 AM
History of the Continental block Thanks to Ron Bolden of QM3 for providing this information.
In the beginning, Continental had two basic blocks, one for the vertical shaft and one for the horizontal shaft engines. The vertical shaft engine block drawing is AA7-B-603. This had a 5 bolt head. From 1947 through 1954 this drawing had gone through Rev. "Z". It was re- drawn in Feb. 1954, and the last revision was made 5-27-57, Rev. # "AC". It was obsoleted in 1957.
The horizontal shaft engine block was originally on drawing AA7-B- 600. This too had a 5 bolt head, and the flywheel side of the block had a hole, approximately 2" in diameter, similar to today's block machined for a side bearing adapter. This casting was introduced in 1947 and was replaced by drawing AA7-B-603 in 1950 and this casting's design had the stator plate mounting bosses on the flywheel side of the block, but it was still a 5 bolt cylinder head. That casting also called for part number AA7-B-527 to be cast on the inside of the block. In 1952 that casting was revised for a 7 bolt head, which replaced the 5 bolt head in 1953 model engines. in 1954, the basic AA7-B-603/AA7-B-527 casting was replaced by a whole new casting, AA7- B-611.
The AA7-B-611 casting is the "Continental" block you are most familiar with. But this casting could have had part numbers AA7-B- 611, AA7-B-532, or AA7-B-548 cast onto it. So the same basic casting had 3 possible numbers on it. AA7-B-611 was the basic casting number. AA7-B-532 was cored for a cylinder bore of 2 1/8" to 2 1/4". The AA7- B-548 casting was cored for a 2 5/16" bore. This was done for less metal. removal in the machining process as Continental produced 3 bore sizes, and 59 block configurations out of this same block.
Now to date your block is a little more difficult. If your Continental block has AA7-B-532, AA7-B-548, or AA7-B-611, it was made sometimes after 1953. The letter "C" on the block stands for Clio Foundry. The other letter stands for the revision date. But it's not that simple either. The number AA7-B-532 was cast on 2 different blocks. The basic AA7-B-611 (2-7-55) and an older block AA7-B-603, (used on a vertical shaft engine), and that dates from 2-2-54. So the revision dates alone are not enough to date your block. You'll need a description of the revisions. So heres the significant revisions and their dates. Keep in mind after the drawing revision was made it took approximately 6 months for that revision to be incorporated into production models.
Rev. "B" 5-27-57 Port size under the valve seat changed from 3/4" to .807/.812". That may be machined "out" in your block, so you can't tell. Rev. "C" 11-15-57 There were 22 changes made to the block under this revision and most of those changes were revised again under revision "H" and "K", see below. The changes you may be able to identify is the thickness of the exhaust flange, changed from 23/32" to 29/32", the addition of the backplate mounting boss at the back of the block close to the pan face toward the flywheel side of the block, and the other significant change was the addition of 2 bosses inside the block that the ignition plate bolted into. So if you exhaust flange thickness was not altered, the backplate mounting boss is missing, and those two plate mounting bosses are not inside your block, your block pre-dates 1958 and it would be safe to say it was produced between 1954-1957.
Rev. "F" 4-22-58. There were 13 changes made under this revision. Most of these changes pertained to the bosses and holes on the top of the block where the ignition plate mounts. It might be tough to identify a block with this revision but the mounting plate changed from a round plate to elongated plate and therefore 2 # 10-24 tapped holes were removed and a 1/4-20 tapped hole was added
Rev. "G" 12-24-58 The two valve spring bosses were added inside the tappet box chamber, not identifiable today if you have guides installed.
Rev. "H" 1-29-60 Go back to revision "C" Those two bosses added to the inside of the block for the ignition mounting plate holes, the height of those bosses was increased from 5/16" to 7/16".
Rev. "J" 2-7-62 This famous revision was a Material change only. The original material specified was S.A.E. 120 Cast Iron Alloy with a base composition of 0.40 Chromium and 0.25 Molybdenum. Revision "J" changed this to: 2.20 - 2.55 Silicon, .55 -.75 Manganese, .130 Max. Sulphur, .300 Max. Phosphorus, and 3.30 - 3.55 Total Carbon.
Rev. "K" 2-7-62 The exhaust flange thickness was increased from 27/32" (see Rev.C) to 1 1/32".
Rev. "L" 5-23-62 The exhaust flange thickness was changed again, from 1 1/32" (see Rev K) to 1.00".
Rev "M" 11-12-63 Last revision made by Continental, which were simply adding dimensions from the centerline of the cylinder bore to the radii dimensions of the stator plate mounting bosses.
These revision letters and explanation of the changes, this may help you history buffs date your Continental block somewhere between 1954 and 1970 when Deco Grand had new patterns made with the number AA7-B- 700S cast on the back. By the way, Deco Grand went up to Revision "W" between 6-7-71 and 7-9-90 including another material change to "Meehanite Alloy". But at least they dated their blocks. We will date and assign a serial number to our blocks. Hope this helps.
mjodrey and MH81 have said thanks