Engine Identification
As we got into this project, one of our fellow Buick guys offered up this engine for the testing. So our first requirement is to determine what year the motor is. The following are the locations and numbers for the various year 455's.
This is the engine, as it was delivered to the shop. Other than the fact it is painted the wrong color, it appears to be a reasonably complete 455 Buick, freshly rebuilt.
On this particular motor, there are several ways to identify it, thru casting numbers, and VIN codes. The casting numbers will get you close, the VIN will give you the exact year. Also, a two digit Production code was stamped on the block surface, between Number 5 and 7 cylinders, but as is often the case in a rebuild, the decks have been machined, and that stamping is long gone.
First, we look at the easiest way to determine the range of the year this engine was produced. By looking at the casting number, located on the back of the engine, between the "ears" that the trans bolts to.
There is no need to try and remember all the numbers.. you just need to know the last 3 of each.
This is a "735" Block, which was produced from Mid year 1972 thru the end of the 455 production, in 1976. This is the most common block you will find in Salvage yards, for sale on internet boards, or in local publications.
The other 455 casting numbers are:
1231738- Or what is known as a "738" block- This engine block is probably the most desirable among those of us doing restorations, as this would be the original casting number for the 70-mid year 71 455's. The early motors had a 1/2 oil pickup tube and the corresponding 1/2 hole in the block, which is shown in the picture below.
There is some debate over the sizing of this hole. It has long been believed that all 70 455's had a 1/2 inch hole, and oil pan pickup, and that the Stage 1 version in 1970 had this hole resized to 5/8, and a bigger pickup installed. I can tell you from personal inspection and experience, that this may not always have been the case. While this statement is generally true, as is the belief that all 455's received the larger hole and pickup for 71 and later, there are exceptions to these rules. I have seen what I believe to be original untouched engines with the following:
1970 Stage 1 motors with:
a 1/2 inch pickup and hole
a 5/8 pickup but still the 1/2 hole
a 5/8 pickup and 5/8 hole (most common)
1970 Standard (non stg 1) engines with:
5/8 pickup tubes and holes
1/2 pickup tubes and holes (most common)
1971 455's (STG and non STG)
5/8 pickup tubes and holes (most common)
1/2 pickup tubes and 5/8 holes
5/8 Pickup tubes with 1/2 holes.
Now, the reason that I go into this so deeply is simply this... this will be our first example of how the "accepted truth" is not always reality. While it is true that in most cases, 1970 455's had a 1/2 pickup tube and feed hole, and that the factory upgraded the STG 1 motor to a 5/8 pickup tube and hole, and that all 71 and later 455's had the 5/8 hole and tube, this is not a rock solid rule. As with every part on the car, these were running production changes, and nobody shut the line down, if the wrong part or hole size came up on the particular block they were assembling. They screwed the part on, and sent it down the line.
It's important that all budding Buick restorers and hobbyists accept this fact to be the truth, as it will avoid many an internet or bench racing argument. Also, having a full understanding of the nuances of the oil pickup tube hole size, will help in quick identification of the 738 block.. it is a certainty, that if you walk into a guy's garage, and see a bare block sitting on it's end, and it has a small pickup tube hole (1/2, easily identifiable as it is the same size as the pressure hole above it) then your looking at a 1970 or early 71" 738" 455 block, which most probably was not originally a STG 1. Now, if the seller/owner claims that it is an original STG 1 block, then you will have to inspect for the production code on the LH deck surface, which we will get into later. What your most likely looking at is a 70 non-stage 455 block, but it's good to know what I have stated above, since there are very few hard fast rules, when it comes to casting numbers, date codes, and hole sizes.
There is one other block casting number out there, which is the 1238861 block, or the "861" block. This block was used from Mid year '71 thru mid year '72. All 861, and the later 735 blocks that I have worked with, have the larger pickup tube and oil feed hole. The only variation I have seen in this is with the 738 block.
Now, back to our "735" block, and more discussion as to other identification methods.